Notes of programming

ITCP / Programming Techniques / Programming Fundamentals of 86

Programming Language Generations Programming Language Generations are used to represent the major steps or generations in the evolution of programming languages. Generations of programming languages are categorized into 5 categories and are: • First Generation of Programming Language or 1GL

Machine language is considered to be the first generation of programming language. In machine language the level of instructions and data that the processor is actually given to work on conventional computers is a string of 0s and 1s. So, the language of 0s and 1s, i.e. machine language is known to be the first generation of programming languages.

• Second Generation of Programming Language or 2GL

2GL or second generation language is Assembler (sometimes called Assembly language). A typical 2GL instruction looks like this:

ADD 12, 8

An assembler converts the assembly language statements into machine

language. • Third Generation of Programming Language or 3GL

Third generation languages are called High-Level programming languages such as C/C++, Pascal or Java etc. A sample Java language statement looks like this:

public static void main(String args[]) {

System.out.println(“Hello Everyone”); }

High-level languages are near to English and the program created in a high-level language is called source program. Compiled type languages i.e. C/C++, Pascal, COBOL and Fortran etc and Interpreter based languages i.e. QBasic, GW-Basic and Visual Basic etc are 3GL.

• Fourth Generation of Programming Language or 4GL

Fourth generation programming language or 4GL is designed to be closer to natural language than a 3GL. Language for accessing databases are often described as 4GLs. A 3GL language statement might look like this:

SELECT NAME FROM EMPLOYEES WHERE SALARY > $7000

• Fifth Generation of Programming Language or 5GL

In fifth generation of programming languages, we use a visual or graphical development interface to create source language that is usually compiled with a 3GL or 4GL compiler. IBM, Microsoft, Borland and other companies make 5GL programming products.


Introduction to C-Language C was created by Dennis Ritchie at Bell Labs in 1972, while working to develop Unix Operating System. It came from Ken Thompson’s B-Language written in 1970.

Levels of Programming Languages There are 3 levels of programming languages i) High-Level Language ii) Middle-Level Language iii) Low-Level Language i) High-Level Language

High-Level Language is designed to try to give programmers everything they could possible want already built into the language.

Following are the high-level languages:

• ADA • BASIC • COBOL • FORTRAN • Pascal

ii) Middle-Level Language

Middle-Level Language gives programmers a minimal set of control to define high-level constructs.

Following are the middle-level languages:

• C/C++ • FORTH

iii) Low-Level Language

Low-Level Language forces programmers to define all program functions directly because nothing is built in the language. Following are the low-level languages:

• Assembly

C is one of a smallest programming language. It has almost 33 reserve words but

doesn’t restrict the programming style. C is often called a middle-level language.


Advantages of using C-Language Following are the advantages of using C-Language

i) Structured Format

C offers top-down structured programming approach. C also allows separately compiled sub-routines to be used without being the part of the program.

ii) Flexibility Being a general-purpose programming language it can be used for solving engineering problems or for writing database systems etc

iii) Portability

Programs written on one system can be run on another system with little or very minor modifications.

iv) Compactness & Efficiency

Programs written in C-Language generate fast and compact code. Programs compiled by C compilers can run about as fast as those written in Assembler.

v) Personalization

In addition to the built-in functions, C-Language allows the user to add his own functions to the language. So it can be personalized to fit one needs.

Uses of C/C++ Programming Language

C is meant for designing Operating Systems. 90% of the Unix code is written in C. Areas other than system programming where C-Language can be used are • Operating Systems • Network Drivers • Communication Packages • Data Bases • Language Interpreters • Utilities • Language Compilers • Spreadsheets • Text Editions • etc etc

C/C++ Character Set C/C++ character set comprises of following characters A,B,C,….Z A,b,c,…...z 0,1,2,……9 , . ; : ? ! “ / ‘ \ | ~ ( ) [ ] { } < > + - # % _ ^ = & *


White Space Characters The character that produces blank space when printed is called a white space character, e.g. • Spaces • Tabs • New Lines

Tokens A group of characters separated by white space is known as a Token. Following are the classes of tokens. i) Keywords

Keywords are the words that make up the C/C++ programming language. Keywords have special meaning to the C/C++ compiler, so they can not be used for other than as a keyword. These must be entered in lower case.

ii) Identifiers

Identifiers are used to describe the names of variables, constants and functions in C/C++, and are also known as Programmer Supplied Words.

iii) Constants

A data object whose pre-set value does not change during the execution of the program is known as constant, i.e. pie.

iv) Variable

Variable is a data object whose value may change during the execution of the program.

v) Functions

Functions are routines to perform commands or operations etc, and may return a value to the calling routine.

vi) String Literals

String Literals are also called a String Constant. It is a sequence of characters surrounded by double quotes. A null byte \0 is appended to the string so that programs that scan the string can find its end.

vii) Operators

Operators are symbols that define how values are manipulated. Operators describe the action that we want to take between the operands.

viii) Other Separators Other Separators are also using in C/C++.


Naming Rules in C/C++ Following are the naming rules in C/C++

• Can contain letters, digits and underscores. • Digit can not be the first character. • Spaces are not allowed. • May not be same as keyword or function name etc. • First 40 characters are significant, i.e. Length can be of max. 40 characters, but

varies from compiler to compiler. • Can not consist of an underscore alone.

Data types and Sizes There are three main data types in C/C++

i) Character char ii) Integer int iii) Floating Point float i) Character data type

Character data type is represented by char and is used for storing a character, digit or special character. A character constant must be enclosed in single quotations i.e. ‘A’, ‘1’ or ‘*’ etc. A variable declared as character uses/occupies one byte of memory.

A character constant can be signed or unsigned.

• The range of binary numbers in signed char is from -128 to +127 • The range for binary numbers in unsigned char is from 0 to 255

So, there are 3 types of character data type, i.e. char, signed char and unsigned char. e.g. • char age means signed char • signed char code means signed char • unsigned char value means unsigned char

ii) Integer data type

Integer data type is represented by int and is used for storing Integers, i.e. numeric values without decimal portions.

• Integer variable can store a value ranging from -32,768 to + 32,767 • Integer data type uses 2 bytes of memory • Integer data type is also represented as short • Another integer type to store larger values is long that can store a value

ranging from -2,147,483,648 to 2,147,483,647 • long takes 4 bytes of memory


• Another int type is signed int which is used to store sign too along with the numeric value.

• Another int type is unsigned int which is used to store values without sign

So, there are 9 types of Integer data types, i.e. int, short, signed int, unsigned int, signed short, unsigned short, long, signed long and unsigned long e.g.

• int a means signed int • signed int b means signed int • unsigned int c means unsigned int • short d means signed short • signed short e means signed short • unsigned short f means unsigned short • long g means signed long • signed long h means signed long • unsigned long i means unsigned long

iii) Float data type

Float data type is represented by float and is used for storing numeric values along with fraction or decimal portion. Float data type takes 4 bytes of memory. A floating point number is expressed in scientific notation. The reason of storing float values in scientific notation is that they can be very large or extremely small, i.e.

2000000000000000 = 2e+15 0.00000000000023 = 2.3e-13

A value written as 47e3 means 47 x 103

• Exponent value ranges from -38 to +38, i.e. 47x10-38 to 47x10+38 • Another float type is double that takes 8 bytes of memory. • Exponent values in double ranges from -308 to + 308, i.e. 47x10-308 to

47x10+308

47e3 = 47 x 103

mantissa exponent


Types of C/C++ Instructions There are 4 types of C/C++ Instructions. i) Type declaration Instructions Variable types and definitions etc. ii) Input/Output Instructions Data Input, Data Display, Data Write etc iii) Control Instructions Controls the sequence of execution of the program instructions. iv) Arithmetic Instructions Arithmetic Operations etc


Preprocessor Directive # is called Preprocessor Directive. The # line tells the compiler to use a file <iostream.h> or <stdio.h> or whatever written in <angle brackets>. Files having .h extension in C/C++ are called header files. They are also sometimes called include files. The iostream.h file is included in the program as it contains the information about the “cout” identifier and the << operator. Normally all the header files of C/C++ are present in the INCLUDE directory.

Main Function A C/C++ program may consist of many functions, classes and other program elements, but on startup, control always goes to main() function. The first statement executed by the C/C++ compiler will be the one that is the first statement in function void main(void) or void(main) or main(). In C/C++ all the statements of a function, either it is main() or any other should be in blocks. A block starts with { (starting brace), then we write statements in the function, and at the end we put } (closing brace), in order to tell the compiler that the above written statements within the block are the statements of a function. The body of a function starts from { and ends at }. Every starting brace should have a closing brace. The statement cout<<”Welcome to C++”; displays the string constant “Welcome to C++” on the screen. We can have one or more statements inside a function. Statements tell the computer to do something. C/C++ statements are always terminated by semicolon.

#include <stdio.h> void main(void) {

printf(“Welcome to C”); }

Preprocessor Directive and is the only thing that should be present in the first column

Statement Terminator

<stdio.h> search function in the directory in which C in installed. “stdio.h” search function in the directory which is presently in use.

Function body

First Program in C

#include <iostream.h> void main(void) {

cout<<“Welcome to C++”; }

Preprocessor Directive and is the only thing that should be present in the first column

Statement Terminator

Function body

First Program in C++


Using Comments in the Program

There are two ways of specifying comments in C++. i) Using // ii) /* and */

All the lines between /* and */ are treated as comments and are normally used when we want to specify many lines as comments. So if we want the C++ compiler to treat some continuous lines as comments then instead of using // at the start of all those lines, it is better to use /* from starting line and */ after the last line and all the lines between starting and ending comments will be treated as comments and will not execute.

// It is a C++ Program #include <iostream.h> void main(void) //main function { /* These lines are the part of comments and will not execute */ cout<<"We are studying C++"; }

Defining and using Integer Variables 1.cpp

#include <iostream.h> void main(void) { int a; int b; a = 10; b = a + 5; cout<<"A is "<<a <<endl; cout<<"B is "<<b <<endl; }

Output A is 10 B is 15


2.cpp #include <iostream.h> #include <conio.h> void main(void) { int a,b; a = 10; b = a + 5; clrscr(); cout<<"A is "<<a <<" and B is "<<b<<endl; cout<<"Press any key to finish"; getch(); }

Output A is 10 and B is 15 Press any key to finish

Variable Definition and Declaration 3.cpp

#include <iostream.h> #include <conio.h> void main(void) { clrscr(); char first=65; int second=964; float third=5.543; cout<<first<<endl<<second<<endl<<third; getch(); }

Output A 964 5.543

Using Escape Sequences in the Program 4.cpp

#include <iostream.h> #include <conio.h> void main(void) { clrscr(); cout<<"Hello\nHow\nAre\nYou\n"; cout<<”Hello\n\tHow\n\t\tAre\n\t\t\tYou\n”; getch(); }

Output Hello How Are You Hello How Are You


Escape Sequences \ is considered an escape sequence character that causes and escape from the normal interpretation of a string so that the next character is recognized as having a special meaning. Following are the escape sequence characters along with their usage.

Escape Sequence Character \a Audible Alert \b Backspace \f Form feed \n New Line (Carriage Return + Line Feed) \r Return \t Tab \\ Backslash \’ Single quotation \” Double quotation

\xDD i.e. \xDB Hexadecimal Representation

Taking Input in the Program 5.cpp

#include <iostream.h> #include <conio.h> void main(void) { clrscr(); int a, b; cout<<"Enter first value "; cin>>a; cout<<"Enter second value "; cin>>b; cout<<a<<" + "<<b<<" = "<<a+b; getch(); }

Output Enter first value 4 Enter second value 3 4 + 3 = 7


The const Qualifier The keyword const (for constant) precedes the data type of a variable. It specifies that the value of a variable will not change throughout the program.

Temperature Conversion Program 6.cpp

#include <iostream.h> #include <conio.h> void main(void) { clrscr(); int fah; cout<<"Enter Temperature in Fahrenheit "; cin>>fah; int cel = (fah - 32) * 5/9; cout<<"Equivalent temperare in Celcius is "<<cel; getch(); }

Output Enter Temperature in Fahrenheit 32 Equivalent temperare in Celcius is 0

Calculating the Area of a Circle 7.cpp

#include <iostream.h> #include <conio.h> void main(void) { clrscr(); float radius; const float PIE = 3.14; cout<<"Enter radius of circle "; cin>>radius; float area = PIE * radius * radius; cout<<"Area of the circle is "<<area; getch(); }

Output Enter radius of circle 0.5 Area of the circle is 0.785

Type Conversion 8.cpp

#include <iostream.h> #include <conio.h> void main(void) { clrscr(); int count=7; float weight=200.5; double totalweight = count * weight; cout<<"Total weight calculated is "<<totalweight; getch(); }

Output Total weight calculated is 1403.5

So, if we try to perform some Arithmetic operation on different data types, i.e. int, float and double etc then C/C++ calculates the result of such type of Arithmetic expression without giving any error.


Casts Cast is a way through which we change the type of the variable during the execution of the program for a limited time, because variables previously defined type can not calculate the values correctly due to its low range.

Arithmetic Operators Following are the basic Arithmetic operators used in C/C++: i) + (Addition) ii) - (Subtraction) iii) * (Multiplication) iv) / (Division) Apart from the specified basic operators, there are some other operators used in C/C++, and are v) % (Remainder or Modulus) vi) ++ (Increment) vii) -- (Decrement) viii) += (Increment Assignment) ix) -= (Decrement Assignment) x) *= (Multiplication Assignment) xi) /= (Division Assignment) xii) %= (Remainder Assignment) Increment and Decrement operators can be used in two ways, i.e. i) Prefix ii) Postfix

9.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); int test=25000; //range is -32,768 to +32,767 test = (test * 10)/10; cout<<"Result is "<<test<<endl; test = 25000; test = (long(test)*10)/10; cout<<"Result now is "<<test; getch(); }

Output Result is -1214 Result now is 25000


10.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); int a=5,b=2; cout<<"A = 5 and B = 2"<<endl<<endl; cout<<"A B"<<endl<<endl; cout<<a<<" + "<<b<<" = "<<a+b<<endl; cout<<a<<" - "<<b<<" = "<<a-b<<endl; cout<<a<<" x "<<b<<" = "<<a*b<<endl; cout<<a<<" / "<<b<<" = "<<a/b<<endl; cout<<a<<" % "<<b<<" = "<<a%b<<endl<<endl; a=5; cout<<"Value of A now is "<<a<<endl<<endl; cout<<"Prefix operator ++a gives "<<++a<<endl; cout<<"Value of a after Prefix is "<<a<<endl<<endl; cout<<"Postfix operator a++ gives "<<a++<<endl; cout<<"Value of a after Postfix "<<a<<endl<<endl; cout<<"Now for A = 5 and B = 2"<<endl; a=5,b=2; a+=b; cout<<"a += b means value of a is "<<a<<endl; a=5,b=2; a-=b; cout<<"a -= b means value of a is "<<a<<endl; a=5,b=2; a*=b; cout<<"a *= b means value of a is "<<a<<endl; a=5,b=2; a/=b; cout<<"a /= b means value of a is "<<a<<endl; a=5,b=2; a%=b; cout<<"a %= b means value of a is "<<a<<endl; getch(); }

Output A = 5 and B = 2 A B 5 + 2 = 7 5 - 2 = 3 5 x 2 = 10 5 / 2 = 2 5 % 2 = 1 Value of A now is 5


Relational Operators A relational operator compares two values. Comparisons involved in relation operators can be i) < Less than ii) > Greater than iii) == Equals to iv) != Not equals v) <= Less than or equals vi) >= Greater than or equals The result of comparison is either True or False. If a comparison provides 1, it means True and if it provides 0, it means False.

Prefix operator ++a gives 6 Value of a after Prefix is 6 Postfix operator a++ gives 6 Value of a after Postfix 7 Now for A = 5 and B = 2 a += b means value of a is 7 a -= b means value of a is 3 a *= b means value of a is 10 a /= b means value of a is 2 a %= b means value of a is 1

11.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); int number; cout<<"Enter a Number "; cin>>number; cout<<"number < 10 = "<<(number<10)<<endl; cout<<"number > 10 = "<<(number>10)<<endl; cout<<"number == 10 = "<<(number==10)<<endl; getch(); }

Output Enter a Number 10 number < 10 = 0 number > 10 = 0 number == 10 = 1


Using Library Functions 12.cpp

#include <iostream.h> #include <conio.h> #include <math.h> void main(void) { clrscr(); int a; cout<<"Enter a value "; cin>>a; cout<<"Square Root of "<<a<<" is "<<sqrt(a); getch(); }

Output Enter a value 64 Square Root of 64 is 8

13.cpp #include <iostream.h> #include <conio.h> #include <math.h> void main(void) { clrscr(); float a; cout<<"Enter a value "; cin>>a; cout<<"Sine of "<<a<<" is "<<sin(a)<<endl; cout<<"Cosine of "<<a<<" is "<<cos(a)<<endl; cout<<"Tangent of "<<a<<" is "<<tan(a)<<endl; getch(); }

Output Enter a value 10 Sine of 10 is -0.544021 Cosine of 10 is -0.839072 Tangent of 10 is 0.648361


Loops Loops cause a section of program to be repeated certain number of times. As long as condition remains true, the repetition continues, when the condition becomes false, the loop ends and the control passes to the statement following the loop. There are three kinds of loops in C/C++. i) for loop ii) while loop iii) do while loop

The for loop The for loop executes a section of code a fixed number of times. for loop is used normally when we know, before entering the loop, that how many times we want to execute the code.

True

Initialization Expression

Test expression

Body of the loop

Increment /decrement expression

ExitFalse

Operation of for loop

for ( initialization expression ; test expression ; increment/decrement expression ) statement; //single statement in loop body for ( initialization expression ; test expression ; increment/decrement expression ) { statement 1; statement 2; . . . statement n; }

syntax of for loop

Multiple statements in loop body


14.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); int sum=0; for(int a=1;a<=10;a++) { cout<<a<<"\t"<<(11-a)<<endl; sum += a; } cout<<"Sum is "<<sum; getch(); }

15.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); int t; cout<<"Enter Table value ";cin>>t; for(int a=1;a<=10;a++) cout<<t<<" x "<<a<<" = "<<(t*a)<<endl; getch(); }

16.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); int num, fact=1; cout<<"Enter a number ";cin>>num; for(int a=num;a>0;a--) fact *= a; cout<<"Factorial of "<<num<<" is "<<fact; getch(); }

Nested for loop

17.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); for(int a=1;a<=2;a++) for(int b=1;b<=3;b++) cout<<"A is "<<a<<" & B is "<<b<<endl; getch(); }

Output 1 10 2 9 3 8 4 7 5 6 6 5 7 4 8 3 9 2 10 1 Sum is 55

Output Enter Table value 7 7 x 1 = 7 7 x 2 = 14 7 x 3 = 21 7 x 4 = 28 7 x 5 = 35 7 x 6 = 42 7 x 7 = 49 7 x 8 = 56 7 x 9 = 63 7 x 10 = 70

Output Enter a number 4 Factorial of 4 is 24

Output A is 1 & B is 1 A is 1 & B is 2 A is 1 & B is 3 A is 2 & B is 1 A is 2 & B is 2 A is 2 & B is 3


The while loop Normally in for loop we have an idea that how many times we want to execute a section of code but while loop is used when even before starting the loop we have no idea that how many times a section of code will be executed. Like for loop, while loop contains a test expression but there is no initialization or increment/decrement expression etc.

True

FalseTest expression

Body of the loop

Exit

Operation of while loop

while ( test expression ) statement; //single statement in loop body while ( test expression ) { statement 1; statement 2; . . . statement n; }

syntax of while loop


18.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); int a=1; while(a<=10) { cout<<a<<"\t"<<(11-a)<<endl; a++; } getch(); }

Output 1 10 2 9 3 8 4 7 5 6 6 5 7 4 8 3 9 2 10 1


19.cpp #include <iostream.h> #include <conio.h> void main(void) { clrscr(); char ch='y'; int t, a; while(ch!='n') { clrscr(); cout<<"Enter Table value ";cin>>t; a=1; while(a<=10) { cout<<t<<" x "<<a<<" = "<<t*a<<endl; a++; } cout<<"Continue ";ch=getche(); } cout<<"\nProgram Finished"; getch(); }

20.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a=15; while(a<1 || a>10) { cout<<"Enter a value (1-10) "; cin>>a; } cout<<"Value entered is between 1 - 10"; getch(); }

Output Enter Table value 5 5 x 1 = 5 5 x 2 = 10 5 x 3 = 15 5 x 4 = 20 5 x 5 = 25 5 x 6 = 30 5 x 7 = 35 5 x 8 = 40 5 x 9 = 45 5 x 10 = 50 Continue n Program Finished

Output Enter a value (1-10) 12 Enter a value (1-10) 31 Enter a value (1-10) -5 Enter a value (1-10) 4 Value entered is between 1 - 10


The do while loop The do while loop is used when we want to guarantee that the loop body should execute at least once, whatever the initial state of the test expression contains. In do while loop, the test expression is placed at the end of the loop.

Body of the loop

True

Test expression

FalseExit

Operation of do while loop

do statement; //single statement in loop body

while ( test expression ) ; do { statement 1; statement 2; . . . statement n; } while ( test expression );

syntax of do while loop


21.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a=1; cout<<"Value\tSquare\tCube"<<endl; do { cout<<a<<"\t"<<a*a<<"\t"<<a*a*a<<endl; a++; }while(a<=10); getch(); }

Output Value Square Cube 1 1 1 2 4 8 3 9 27 4 16 64 5 25 125 6 36 216 7 49 343 8 64 512 9 81 729 10 100 1000


22.cpp #include<iostream.h> #include<conio.h> void main(void) { char ch; int t; do { clrscr(); cout<<"Enter Table value "; cin>>t; for(int a=1;a<=10;a++) cout<<t<<" x "<<a<<" = "<<t*a<<endl; cout<<"Continue "; ch=getche(); }while(ch=='Y' || ch=='y'); cout<<"\nThanks for using program"; getch(); }

Output Enter Table value 4 4 x 1 = 4 4 x 2 = 8 4 x 3 = 12 4 x 4 = 16 4 x 5 = 20 4 x 6 = 24 4 x 7 = 28 4 x 8 = 32 4 x 9 = 36 4 x 10 = 40 Continue n Thanks for using program


Decision Making Statements if statement

if statement is the simplest of the decision making statements. if statement executes a set of commands when a specified condition is true. If specified condition is false then simply the commands associated with if condition will not execute.

False

True

Test expression

statement 1; statement 2;

.

.

Exit

Operation of if statement

if ( test expression ) statement ; //single statement in if body if (test expression) { statement 1; statement 2; . . . statement n; }

syntax of if statement

Multiple statements in if body


23.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a; cout<<"Enter a value "; cin>>a; if(a==10) cout<<"Value entered is 10"; if(a<10) cout<<"Value entered is less than 10"; if(a>10) cout<<"Value entered is greater than 10"; getch(); }

24.cpp #include<iostream.h> #include<conio.h> #include<process.h> void main(void) { clrscr(); long n, j; cout<<"Enter a number ";cin>>n; for(j=2;j<n/2;j++) if(n%j==0) { cout<<"It's not prime,

Divisible by "<<j<<endl; getch(); exit(0); } cout<<"It's Prime\n"; getch(); } // The exit() function causes the program to terminate, and value 0 is used here for successful // termination.

Output Enter a value 7 Value entered is less than 10 Enter a value 10 Value entered is 10 Enter a value 13 Value entered is greater than 10

Output Enter a number 3 It's Prime Enter a number 17 It's Prime Enter a number 15 It's not prime, Divisible by 3 Enter a number 13 It's Prime Enter a number 49 It's not prime, Divisible by 7


The if else statement The if else statement executes one or more commands when a condition is true. If condition is false then those commands are ignored and are not executed. if else is used when we want some commands to be executed when a condition is true and if condition is false then another set of commands should be executed.

Operation of if else statement

True

Test expression

Body of if statement 1; statement 2;

Exit

False

Body of else statement 1; statement 2;

if ( test expression ) statement ; //single statement in if body else statement ; //single statement in else body if (test expression) { statement 1; statement 2; . . statement n; } else { statement 1; statement 2; . . statement n; }

syntax of if else statement

Multiple statements in if body

Multiple statements in else body


Counting words and characters in a C/C++ program 25.cpp

#include<iostream.h> #include<conio.h> void main(void) { int chcount=0; int wdcount=1; char ch='a'; clrscr(); while(ch!='\r') { ch=getche(); if(ch==' ') wdcount++; else chcount++; } cout<<"\nWords = "<<wdcount; cout<<"\nCharacters = "<<(chcount-1); getch(); } Counting words and characters with different technique

26.cpp #include<iostream.h> #include<conio.h> void main(void) { int chcount=0; int wdcount=1; char ch; clrscr(); while((ch=getche()) !='\r') { if(ch==' ') wdcount++; else chcount++; } cout<<"\nWords = "<<wdcount; cout<<"\nCharacters = "<<chcount; getch(); }

Output hello how are you Words = 4 Characters = 14

Output hello how are you Words = 4 Characters = 14


27.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a, b, c; cout<<"Enter values for A, B and C "; cin>>a>>b>>c; if(a==b) if(b==c) cout<<"A. B and C are Equal"; else cout<<"B and C are not Equal"; else cout<<"A and B are not Equal"; getch(); }

Defining Label and use of switch, break and goto statements

28.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a, b; char ch; cout<<"Enter 1st value ";cin>>a; cout<<"Enter 2nd value ";cin>>b; again: cout<<"+, -, x, / "; ch=getche(); cout<<endl; switch(ch) { case '+': cout<<a<<" + "<<b<<" = "<<a+b<<endl; break; case '-': cout<<a<<" - "<<b<<" = "<<a-b<<endl; break; case 'x': cout<<a<<" x "<<b<<" = "<<a*b<<endl; break; case '/': cout<<a<<" / "<<b<<" = "<<a/b<<endl; break; default: cout<<"Wrong Choice\n"; goto again; } getch(); }

Output Enter values for A, B and C 5 5 8 B and C are not Equal Enter values for A, B and C 5 3 3 A and B are not Equal Enter values for A, B and C 4 4 4 A. B and C are Equal Enter values for A, B and C 8 6 8 A and B are not Equal

Output Enter 1st value 5 Enter 2nd value 3 +, -, x, / ? Wrong Choice +, -, x, / @ Wrong Choice +, -, x, / % Wrong Choice +, -, x, / & Wrong Choice +, -, x, / + 5 + 3 = 8


The switch statement The switch statement is similar to the if else or else if construct but is more flexible. If decision tree is large, and all the decisions depend on the value of the same variable, then it is better to use switch statement instead of series of if else or else if statements.

The break statement The break keyword causes the entire switch statement to exit. Control goes to the first statement following the end of the switch statement. If break statement is not used then the control passes down to the next case statement and the statements that we do not want to execute, starts executing. If the value of the switch variable doesn’t match any of the case constants then control passes to the end of the switch without doing anything.

switch variable equals

second case body

True

False

Second case body


third case body

True

False

Third case body


first case body

True

False

First case body

Default body

Fourth case body


fourth case body

True

False

Exit

Operation of switch statement

switch(n) {

case 1: Statement; Statement; Break; case 2: Statement; Statement; Break; case 3: Statement; Statement; Break; case 4: Statement; Statement; Break; default: Statement; Statement;

}

Integer or character variable

Integer or character constant

first case body

causes exit from switch

Integer or character constant

second case body

causes exit from switch

default body and no break statement

Syntax of switch statement


Using multiple cases in switch statement 29.cpp

#include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a, b; char ch; cout<<"Enter 1st value ";cin>>a; cout<<"Enter 2nd value ";cin>>b; cout<<"1. Add\n"; cout<<"2. Subtract\n"; cout<<"3. Multiply\n"; cout<<"4. Divide\n"; again: cout<<"Enter your choice (1-4) "; ch=getche(); cout<<endl; switch(ch) { case '1': case 'A': case 'a': cout<<a<<" + "<<b<<" = "<<a+b<<endl; break; case '2': case 'S': case 's': cout<<a<<" - "<<b<<" = "<<a-b<<endl; break; case '3': case 'M': case 'm': cout<<a<<" x "<<b<<" = "<<a*b<<endl; break; case '4': case 'D': case 'd': cout<<a<<" / "<<b<<" = "<<a/b<<endl; break; default: cout<<"Wrong Choice\n"; goto again; } getch(); }

Output Enter 1st value 5 Enter 2nd value 3 1. Add 2. Subtract 3. Multiply 4. Divide Enter your choice (1-4) 7 Wrong Choice Enter your choice (1-4) k Wrong Choice Enter your choice (1-4) S 5 - 3 = 2


The Conditional Operator There is a compressed way of expressing the if else statement and is called the conditional operator.

Operation of conditional operator

True

test expression

Statement 1;

Exit

False

Statement 2;

Test-expression ? statement1 : statement2 ;

Syntax of conditional operator Conditional operator

30.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a, b; cout<<"Enter 1st value ";cin>>a; cout<<"Enter 2nd value ";cin>>b; (a > b) ? cout<<"1st value is greater" : cout<<"2nd value is greater"; getch(); }

Output Enter 1st value 5 Enter 2nd value 3 1st value is greater Enter 1st value 3 Enter 2nd value 5 2nd value is greater


31.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); for(int i=1;i<=8;i++) { for(int j=0;j<20;j++) { char ch=(j%4) ? ' ' : 'x'; cout<<ch; } cout<<endl; } getch(); }

Output x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x


Logical Operators Other than Arithmetic operators, i.e. +, -, *, /, % etc and Relational Operators, i.e. <, >, <=, >= etc, there is another family of operators called the Logical operators.

Logical operators allow the programmer to combine Boolean (True/False) values.

Operator Effect && Logical AND

|| Logical OR ! Logical NOT

Example of the use of Logical Operators is in program 22.cpp in which Logical

OR is used.

32.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int p; do { cout<<"Enter your percentage (0-100) "; cin>>p; } while(p<0 || p>100); if(p>=90) cout<<p<<"% = A+ Grade"; else if(p>=80 && p<90) cout<<p<<"% = A Grade"; else if(p>=70 && p<80) cout<<p<<"% = B Grade"; else if(p>=60 && p<70) cout<<p<<"% = C Grade"; else if(p>=50 && p<60) cout<<p<<"% = D Grade"; else cout<<p<<"% = F Grade"; getch(); }

33.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); char ch='y'; while(!(ch=='n')) { cout<<"\nHello\n"; cout<<"continue ";ch=getche(); } cout<<"\nEnd";getch(); }

Output Enter your percentage (0-100) -5 Enter your percentage (0-100) 121 Enter your percentage (0-100) 78 78% = B Grade Enter your percentage (0-100) 92 92% = A+ Grade Enter your percentage (0-100) 84 84% = A Grade Enter your percentage (0-100) 71 71% = B Grade Enter your percentage (0-100) 62 62% = C Grade Enter your percentage (0-100) 57 57% = D Grade Enter your percentage (0-100) 49 49% = F Grade

Output Hello continue a Hello continue y Hello continue k Hello continue n End Keeps on displaying Hello until ‘n’ is pressed


34.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); char ch='y'; while(ch!='n') { cout<<"\nHello\n"; cout<<"continue ";ch=getche(); } cout<<"\nEnd";getch(); }

Output Same program with same output as 33.cpp but written in different style


Operators Precedence Operators precedence in C/C++ is

Operator Type Operators

Unary !, ++, --, -

Arithmetic *, /, % +, -

Relational <, >, <=, >= ==, !=

Logical and && or ||

Conditional ? :

Assignment =, +=, -=, *=, /=, %=

If we want an expression to be evaluated first even its operators precedence is not

on the top then it can be done by placing parenthesis around it.


The continue statement If we want to come out of the loop we use break statement, similarly if we want to go back to the top of the loop, we use continue statement.

Condition true

continue

Operation of the continue statement35.cpp

#include <iostream.h> #include <conio.h> void main(void) { long divident, divisor; char ch; do { clrscr(); cout<<"Enter Divident ";cin>>divident; cout<<"Enter Divisor ";cin>>divisor; if(divident==0 || divisor==0) { cout<<"Divident or Divisor can not be 0"; getch(); continue; } cout<<divident<<" / "<<divisor<<" = "<<divident / divisor<<endl; cout<<divident<<" % "<<divisor<<" = "<<divident % divisor<<endl; cout<<"Continue "; ch=getche(); }while(ch!='n'); cout<<"\nProgram Finished"; getch(); }

Output Enter Divident 15 Enter Divisor 0 Divident or Divisor can not be 0 Enter Divident 70 Enter Divisor 5 70 / 5 = 14 70 % 5 = 0 Continue y Enter Divident 12 Enter Divisor 2 12 / 2 = 6 12 % 2 = 0 Continue n Program Finished


The goto Statement goto statement is mostly used in structured programming. In order to use goto statement, we insert a label in our program code at the desired location. Label is a user defined name terminated by a colon sign. The keyword goto is followed by the label name that takes the control to the specified label, i.e.

statement; statement; goto again; statement; statement; again: statements in label again; statements in label again;


Structures Structure is a collection of variables that can be of the same or different data types. The data items in a structure are called the members of the structure.

A user can define its own data types using structures. A structure in C/C++ is like a record of other languages, i.e. Pascal etc.

A structure is defined with the name of “part” that consists of three members. The structure specifier doesn’t set aside any space in memory. The structure “part” is like a new data type but we have not yet created any variables of type “part”.

struct structure-name { data-type variable-name; data-type variable-name; . . . }; struct part { int modelnumber; int partnumber; float cost; };

keyword name of the structure or tag

Structure members

Terminating the structure specifier

S1.cpp #include<iostream.h> #include<conio.h> struct Part { int mn; int pn; float cost; }; void main(void) { clrscr(); Part p1; p1.mn=6244; p1.pn=373; p1.cost-217.5; cout<<"Model Number "<<p1.mn<<endl; cout<<"Part Number "<<p1.pn<<endl; cout<<"Cost is Rs. "<<p1.cost<<endl; getch(); }

Output Model Number 6244 Part Number 373 Cost is Rs. 8.697043e-12


Defining Structure Variables A structure variable is defined the same way as a variable of any built-in data type i.e.

int age; // age is a variable of built-in data type Integer

part p1; //p1 is a variable of structure type part

Accessing Structure Members The members of a structure variable are accessed by a dot operator, i.e.

p1.mn = 6244;

p1.pn = 373;

Combining Structure Specifier and Definition Structure specifer and defining structure variables can be combined into a single statement, i.e.

Initializing Structure Members Structure members can be initialized when a structure variable is defined just as variables can be initialized when it is defined, i.e. int a=13; Similarly, An important point to remember is that structure variables can be assigned to one another when they are of the same structure type.

struct { int mn; int pn; float cost; } p1, p2, p3;

Can be done without structure or tag name, but its variables can not be defined any where else in the program

Defined three variables, i.e. p1, p2 and p3

Part p1={6244, 373, 217.5};

Part p2; p2 = p1;

mn pn cost

Assigns p1 to p2. The value of each member of p1 is assigned to the corresponding member of p2.


S2.cpp #include<iostream.h> #include<conio.h> struct Distance { int feet; float inches; }; void main(void) { clrscr(); Distance d1, d2, d3; cout<<"Enter feet for 1st Distance "; cin>>d1.feet; cout<<"Enter inches for 1st Distance "; cin>>d1.inches; cout<<"Enter feet for 2nd Distance "; cin>>d2.feet; cout<<"Enter inches for 2nd Distance "; cin>>d2.inches; d3.inches = d1.inches + d2.inches; d3.feet = 0; if(d3.inches >= 12.0) { d3.inches -= 12.0; d3.feet++; } d3.feet += d1.feet+ d2.feet; cout<<"Total Distance is "<<d3.feet<<"\'-"<<d3.inches<<"\""; getch(); }

Output Enter feet for 1st Distance 5 Enter inches for 1st Distance 7.5 Enter feet for 2nd Distance 6 Enter inches for 2nd Distance 8.5 Total Distance is 12'-4"

Note d3 = d1 + d2; is not allowed as Arithmetic Operators, i.e. +, - etc can not be used with the data types that are defined by the user.


Structures within Structures Structures can be used inside a structure. Structures within structures are crated when we need a structure to be used in another structure. The following program is an example of the implementation of structures within structures.

Initializing Nested Structures Nested structures can be initialized, the way non-nested structures are initialized. The following example shows how the nested structures created in “s3.spp” is initialized.

S3.cpp #include<iostream.h> #include<conio.h> struct Distance { int feet; float inches; }; struct Room { Distance length; Distance width; }; void main(void) { clrscr(); Room dining; dining.length.feet = 13; dining.length.inches = 6.5; dining.width.feet = 10; dining.width.inches = 5.0; float length = dining.length.feet + dining.length.inches / 12; float width = dining.width.feet + dining.width.inches / 12; cout<<"Dining Room Area is "<< length*width <<" Square Feet"; getch(); }

Output Dining Room Area is 141.059036 Square Feet

length

width

feet inches

inches

feet

Room dining = 13, 6.5 , 10, 5.0 ;


Enumerated Data Types Structures can be looked as a way of providing user-defined data types. Another way of defining our own data types is enumerated data type. Enumerated data type is used when a user knows before a list of values that a data type can use. • In enum, every possible value should have a name, i.e. saturday, sunday etc • Variable of enumerated data type, i.e. d1 and d2 can be given any of the value

listed in the enum specifier. • A value that is not listed in enum specifier can not be assigned to an enum

variable. • Arithmetic operators can be used with enum types, i.e. +, -, / etc • Enumerated data types are treated internally as integers. Normally the first name

in the list is given value 0, 1 to second and so on.

enum variable-name { constant1, constant2, . . . . . }; List of constants separated by commas

terminator

S4.cpp #include <iostream.h> #include <conio.h> enum dow{friday, saturday, sunday, monday, tuesday, wednesday, thursday}; void main(void) { clrscr(); dow d1, d2; d1 = monday; d2 = thursday; int difference = d2 - d1; cout<<"Day between Monday through Thursday are "<<difference<<endl; if(d1<d2) cout<<"Monday comes before Thursday"; getch(); }

Output Day between Monday through Thursday are 3 Monday comes before Thursday


Specifying Integer Values In enum specifier first member name gets a value 0, second gets 1 and so on. But the order can be changed, i.e. instead of starting from 0, if user wants to start from 5, then 6 and so on, then it can be done the following way.

enum dow{friday=5, saturday, sunday, monday, tuesday, wednesday, thursday};

S5.cpp #include <iostream.h> #include <conio.h> enum boolean{false, true}; void main(void) { clrscr(); char ch; boolean muslim = false; cout<<"Are you Muslim "; ch=getche(); if(ch=='y' || ch=='Y') muslim = true; if(muslim) cout<<"\nYou are Muslim"; else cout<<"\nYou are not Muslim"; getch(); }

Output Are you Muslim y You are Muslim Are you Muslim n You are not Muslim


Functions A group of statements that perform a specified operation is called a function. In a function we group several program statements into a unit and give that unit a name that is called function name. That function can be invoked any where in the program.

Program statements that appear in the program more than once are suitable for creating a function. Function code is stored in only one place in the memory. Another reason for creating functions is that a complex or bigger program code is divided into different functions due to which it becomes easy to manage the program.

There are 3 things important related to a function. i) Function Declaration ii) Function Calling iii) Function Definition i) Function Declaration

Function Declaration is also called prototyping. Function declaration tells the compiler that at some later point in the program a function will be called. i.e.

void line(void);

The void line(void); is a function declaration. The first void represents that the return type of the function, void means no return type. The name of the function is line. The void in the parenthesis indicates that line function doesn’t take any arguments. Function declaration is terminated with a semicolon.

ii) Function Calling

Executing or invoking the function is called function calling, i.e.

line();

A function is called or executed by its name followed by the parenthesis. The call is terminated by a semicolon.

When the function is called or invoked, then the control goes to the area of the program where the function is defined, i.e. control starts executing the statement that are part of the function. After executing the function, control returns to statement following the function call.

iii) Function Definition

Function definition contains that actual code for the function. The first line of function definition is called the function declarator, that is followed by the function body. Function body is enclosed in braces. Function body contains statements that makeup the function.

Function declarator should have the same name as specified in function prototyping and should have the same number of arguments and return type as a function prototype, i.e.


void line(void) { for(int a=1;a<=20;a++) cout<<”*”; cout<<endl; }

F-1.cpp #include<iostream.h> #include<conio.h> void line(void); //Function Declaration void main(void) { clrscr(); line(); //Function Calling cout<<"Hello"<<endl; line(); cout<<"We are studying functions"<<endl; line(); getch(); } void line(void) //Function Declarator { for(int a=1;a<=20;a++) cout<<"*"; cout<<endl; }

Output ******************** Hello ******************** We are studying functions ********************


Eliminating the Declaration Function declaration can be eliminated in the program if the function definition is specified before the first function call. Although this approach is simpler but is not flexible.

Passing Arguments to Functions

F-2.cpp #include<iostream.h> #include<conio.h> void line(void) //Function Definition without Declaration { for(int a=1;a<=20;a++) cout<<"\xCD"; cout<<endl; } void main(void) { clrscr(); line(); cout<<"Hello"<<endl; line(); cout<<"We are studying functions"<<endl; line(); getch(); }

Output ════════════════════ Hello ════════════════════ We are studying functions ════════════════════


Passing by Value An argument is a piece of data, i.e. a value passes from program to function, and these passed values etc can be used by the function according to the requirements. There are two ways in Passing by Value, through which arguments can be passed to the functions, i.e. i) Passing Constants to functions ii) Passing Variables to functions i) Passing Constants to functions

As the name represents, In passing constants to functions, a character, integer or float constant is actually passed as argument to the function, i.e.

line(‘*’);

square(5);

F-3.cpp #include<iostream.h> #include<conio.h> void chline(char, int); void main(void) { clrscr(); chline('=',10); //Character and Integer constants passed cout<<"Hello"<<endl; chline('*',20); cout<<"We are studying functions"<<endl; chline('-',10); getch(); } void chline(char ch, int n) { for(int a=1;a<=n;a++) cout<<ch; cout<<endl; }

Output ========== Hello ******************** We are studying functions ----------


ii) Passing Variables to functions In passing variables to functions, instead of passing a constant, the value that needs to be passes as arguments is placed/stored in a variable, and that variable is used as arguments, i.e.

line(a);

square(n);

Passing Structure Variables to functions The way we pass constants or variables as arguments to functions of the default data types, we have the capability of passing constants or variables of the structure types.

When passing constants of the structure type, the sequence of the members should be the same as defined in the structures.

Passing Structure Variable to Functions

F-4.cpp #include<iostream.h> #include<conio.h> void chline(char, int); void main(void) { clrscr(); char ch; int n; cout<<"Enter a character "; cin>>ch; cout<<"Enter a value "; cin>>n; chline(ch, n); //Character and Integer variables passed cout<<"Hello"<<endl; chline(ch, n); cout<<"We are studying functions"<<endl; chline(ch, n); getch(); } void chline(char ch, int n) { for(int a=1;a<=n;a++) cout<<ch; cout<<endl; }

Output Enter a character + Enter a value 10 ++++++++++ Hello ++++++++++ We are studying functions ++++++++++


The way we pass variables of default data types to functions, we can pass variables of structure types. Structures should be defined before the function declaration where variables of that structure type is used.

Returning values from Functions

F-5.cpp #include<iostream.h> #include<conio.h> struct Distance { int feet; float inches; }; void showDistance(Distance); void main(void) { clrscr(); Distance d1, d2; cout<<"Enter feet for 1st Distance "; cin>>d1.feet; cout<<"Enter inches for 1st Distance "; cin>>d1.inches; cout<<"Enter feet for 2nd Distance "; cin>>d2.feet; cout<<"Enter inches for 2nd Distance "; cin>>d2.inches; cout<<"\nFirst Distance is "; showDistance(d1); cout<<"\nSecond Distance is "; showDistance(d2); getch(); } void showDistance(Distance dd) { cout<<dd.feet<<"\'-"<<dd.inches<<"\""; }

Output Enter feet for 1st Distance 5 Enter inches for 1st Distance 6.5 Enter feet for 2nd Distance 7 Enter inches for 2nd Distance 8.5 First Distance is 5'-6.5" Second Distance is 7'-8.5"


When a function completes its execution, it can return a single value to the calling program. An important thing to note is that functions can return only a single value. If we want our function to return more than one value, then we can use some other techniques, i.e. If our function returns the value back to a structure variable, an if our structure is a combination of many members of the same or different data types, then it means that one structure variable will be containing more than one members and like this our return values were more than once.

The return statement

F-6.cpp #include<iostream.h> #include<conio.h> float p2k(float); void main(void) { clrscr(); float pounds, kilograms; cout<<"Enter weight in Pounds "; cin>>pounds; kilograms = p2k(pounds); cout<<pounds<<" Pounds = "<<kilograms<<" Kilograms"; getch(); } float p2k(float pounds) { float kilograms = 0.453592 * pounds; return kilograms; }

Output Enter weight in Pounds 200 200 Pounds = 90.718399 Kilograms

Function will return a float type of value

Returned value will be stored in kilograms variable

return 0.453592 * pounds ; or return (0.453592 * pounds) ;


When we call a function than one or more arguments can be sent to a function, but a function can only return one argument. Multiple arguments can not be returned from a function using return statement, but can be made to do so if our return variable is of structure type.

Functions return type should always be included in the function declaration. If function doesn’t return anything then we use void to indicate that function will not return a value.

If a functions return type is not specified in the function declaration then the compiler assumes that functions return type is int. So, if a function is declared as, i.e.

test();

then it means that the function will return an integer type of value on completion, as in its declaration, no return type was specified.

It is better that we always specify the return type even if it is int. This habit makes the program listing consistent and readable.


Returning Structure Variables The way functions return the values of default data types, we can create functions that return variables of structure type.

F-7.cpp #include<iostream.h> #include<conio.h> struct Distance { int feet; float inches; }; Distance sumDistance(Distance, Distance); void showDistance(Distance); void main(void) { clrscr(); Distance d1, d2, d3; cout<<"Enter feet for 1st Distance "; cin>>d1.feet; cout<<"Enter inches for 1st Distance "; cin>>d1.inches; cout<<"Enter feet for 2nd Distance "; cin>>d2.feet; cout<<"Enter inches for 2nd Distance "; cin>>d2.inches; d3 = sumDistance(d1, d2); cout<<"\nFirst Distance is "; showDistance(d1); cout<<"\nSecond Distance is "; showDistance(d2); cout<<"\nSum of Distance is "; showDistance(d3); getch(); } Distance sumDistance(Distance dd1, Distance dd2) { Distance dd3; dd3.inches = dd1.inches + dd2.inches; dd3.feet = 0; if(dd3.inches >= 12.0) { dd3.inches -=12.0; dd3.feet++; } dd3.feet += dd1.feet + dd2.feet; return dd3; } void showDistance(Distance dd) { cout<<dd.feet<<"'-"<<dd.inches<<"\""; cout<<endl; }

Output Enter feet for 1st Distance 5 Enter inches for 1st Distance 6.5 Enter feet for 2nd Distance 8 Enter inches for 2nd Distance 9.5 First Distance is 5'-6.5" Second Distance is 8'-9.5" Sum of Distance is 14'-4"


Passing by Reference In passing arguments by reference, instead of passing a value to the function, its reference that is the address of that variable is passed.

Passing by reference has two main advantages, i.e. i) Function can access the actual variables of the calling function. ii) Provides a mechanism for returning more than one value from the called function

to its calling function.

A reference provides an alias (different name or second name) for a variable.

F-8.cpp #include<iostream.h> #include<conio.h> void swap(int&, int&); void main(void) { clrscr(); int a, b; cout<<"Enter value for a "; cin>>a; cout<<"Enter value for b "; cin>>b; cout<<"\nBefore Swapping"<<endl; cout<<"A is "<<a<<" and B is "<<b<<endl; swap(a, b); cout<<"\nAfter Swapping"<<endl; cout<<"A is "<<a<<" and B is "<<b<<endl; getch(); } void swap(int& aa, int& bb) { int t = aa; aa = bb; bb = t; }

Output Enter value for a 10 Enter value for b 20 Before Swapping A is 10 and B is 20 After Swapping A is 20 and B is 10

Function has not returned any value but even then the variables in the main function have changed value

Passing default data types by reference


Passing Structures by Reference

F-9.cpp #include<iostream.h> #include<conio.h> struct Distance { int feet; float inches; }; void scale(Distance&, float); void show(Distance); void main(void) { clrscr(); Distance d1; cout<<"Enter feet for distance "; cin>>d1.feet; cout<<"Enter inches for distance "; cin>>d1.inches; cout<<"Distance is "; show(d1); scale(d1,0.5); cout<<"Distance now is "; show(d1); getch(); } void scale(Distance& d, float factor) { float inches = (d.feet*12 + d.inches ) * factor; d.feet = inches / 12; d.inches = inches - d.feet * 12; } void show(Distance d) { cout<<d.feet<<"\'-"<<d.inches<<"\""; cout<<endl; }

Output Enter feet for distance 10 Enter inches for distance 6.6 Distance is 10'-6.6" Distance now is 5'-3.299999"


Overloaded Functions Or

Function Overloading Overloaded functions perform different activities depending on the kind of data send to it.

F-10.cpp #include<iostream.h> #include<conio.h> void line(void); void line(int); void line(char); void line(int, char); void line(char, int); void main(void) { clrscr(); line(10); line(); line('=',15); line('*'); line(20,'-'); getch(); } void line(void) { for(int a=1;a<=10;a++) cout<<"*"; cout<<endl; } void line(int n) { for(int a=1;a<=n;a++) cout<<"*"; cout<<endl; } void line(char c) { for(int a=1;a<=10;a++) cout<<c; cout<<endl; } void line(int n, char c) { for(int a=1;a<=n;a++) cout<<c; cout<<endl; } void line(char c, int n) { for(int a=1;a<=n;a++) cout<<c; cout<<endl; }

Output ********** ********** =============== ********** --------------------


Overloaded function or Function overloading means that more than one function with the same name exists in the program. Same function name would be declared and defined in the program more than once, differing in the number of arguments.

When the function will be called, then number of arguments will decide that which function will be actually called, i.e.

void line();

void line(int);

void line(char);

void line(int, char);

void line(char, int);

We can see the above mentioned declarations that all five functions have the same name, i.e. line, but every functions prototype is different from one another, and similarly, when we’ll call the function line than its number of arguments will decide, which function to execute.

Function definition doesn’t need to be in sequence the way functions are declared, but only requirement is that the number of function definitions should be equal to the number of function declarations.


Different types of Arguments in Overloaded Functions or

Arguments of different data types in Overloaded Functions In overloaded functions, the compiler can distinguish even if we provide different types of arguments in the functions. The following program has overloaded function with the name of show that has two different types of arguments, i.e. one is of float type and other is of structure type. On calling the function, the arguments decide that will function we want to overload. So, if we send arguments of float type than the function having float type arguments is overload or if we send structure type arguments, then function having structure type arguments is overloaded.

F-11.cpp #include<iostream.h> #include<conio.h> struct Distance { int feet; float inches; }; void show(Distance); void show(float); void main(void) { clrscr(); Distance d1; float allinches; cout<<"Enter feet for distance "; cin>>d1.feet; cout<<"Enter inches for distance "; cin>>d1.inches; cout<<"Enter complete distance in inches "; cin>>allinches; cout<<<"\nFirst distance is "; show(d1); cout<<<"\nSecond distance is "; show(allinches); getch(); } void show(Distance d1) { cout<<d1.feet<<"\'-"<<d1.inches<<"\""<<endl; } void show(float ai) { int feet = ai / 12; float inches = ai - feet * 12; cout<<feet<<"\'-"<<inches<<"\""<<endl; }

Output Enter feet for distance 5 Enter inches for distance 5.5 Enter complete distance in inches 95 First distance is 5'-5.5" Second distance is 7'-11"


Default Arguments in Function Declaration and Calling A function can be called without specifying all its arguments, if in function declaration we provide default values for the arguments that are not specified.

When the function is called, the missing argument is assumed to be the last argument. Missing arguments should always be the trailing arguments.

F-12.cpp #include<iostream.h> #include<conio.h> void line(char='*', int=20); void main(void) { clrscr(); line(); line('='); line('-',10); getch(); } void line(char ch, int n) { for(int a=1;a<=n;a++) cout<<ch; cout<<endl; }

Output ******************** ==================== ----------


Inline Functions In order to prevent repeating some statement again and again in a program we create function of those statements. Function reduces program code and program seems to be well organized. Whenever a function is called, the control jumps from main program code to the function code and this process requires saving the information of main program and then loading the information of called function that reduces or wastes sometime. If a function that has long code then it is only a small time but if a function is small, i.e. only one or two statements than it is better to repeat it in the program instead of creating its function as it will be wasting more time. Although in this way the program code will become lengthier and program organization will not be as clear as it become in the case of functions, but the benefit in this way will be reduced execution time. Program will run faster but program listing will be longer and more complex A solution to this problem is inline functions. Inline functions are written like normal functions but compiles into inline code instead of into a function. The program remains well organized as function is shown as a separate entity but when the program is compiled, the function body is inserted into the program whenever a function call occurs. Very small functions, i.e. which have one or two statements are candidates to be inlined. For inline functions, the compiler must have seen the function definition (not only the declaration), because it inserts the actual code into the program. So, for inline function, function declaration can be eliminated. Inline keyword is used before that function prototyping to tell the compiler that a function is inline, i.e.

inline float ps2kg(float pounds) { return 0.453592 * pounds; }

F-13.cpp #include<iostream.h> #include<conio.h> inline float p2k(float pounds) //inline function { return 0.453592 * pounds; } void main(void) { clrscr(); int pounds; cout<<"Enter weight in pounds "; cin>>pounds; cout<<pounds<<" Pounds = "<<p2k(pounds); cout<<" Kilograms"; getch(); }

Output Enter weight in pounds 180 180 Pounds = 81.646561 Kilograms


Storage Classes of Variables There are three storage classes of variables i) Automatic Variables ii) External Variables iii) Static Variables i) Automatic Variables

Variables defined within function body are called automatic variables. Keyword auto can be used to specify an automatic variable, i.e.

void main(void) { auto int age; Auto char grade; . . . }

void ps2kg(void) { auto float pounds; . . }

As auto is default, i.e. a variable created within a function is always

automatic, even if it is not specified, so it is very rarely used. Automatic variable is also called local variable as it is visible only locally in the function where it was created. Local or Automatic variables are stored on the stack, that grows downward in the memory.

Automatic variable or Local variable has two important characteristics, i.e. Lifetime and Visibility.

Lifetime An automatic variable is not created until the function in which it is defined is called. A variable created in a function will occupy memory for storing values only when the function in which it is defined will execute. The variable will be destroyed and its value will be lost and the memory it has occupied will be released as soon the control transfers from the function in which it was defined. The time period between the creation and destruction of a variable is called lifetime or duration. The lifetime of an automatic variable depends upon the execution of the function in which it is defined. Limiting the lifetime of automatic variables saves memory. If a function is not executing then the variables it uses during execution are only needed when that function executes so removing them when function is not executing frees up memory that can be used by other functions.


Visibility Variables visibility describes where within a program it can be accessed. Automatic variables are only visible and can be accessed within the function in which they are defined. So, the scope of automatic variable is the part of the program where the variable is visible.

A programmer can be confident by limiting the visibility of the variables that no function can accidentally change the values of variables defined in other functions.

Limiting the visibility is an important feature of Object-Oriented Programming. An automatic variable that is created but not initialized contains garbage values.

ii) External Variables

External variables are defined outside of (external to) any function. An external variable is visible to all the functions in a program. External variables are also called Global Variables, as they are known by all the functions in a program. External variables normally are defined at the beginning of the listing so they are visible to all the functions.

#include <iostream.h> #include <conio.h> char ch=’a; void getchar(); void putchar(); void main(void) { clrscr(); while(ch!=’\r’) { getchar(); Putchar(); } } void getchar() { ch=getch(); } void putchar() { cout<<ch; }

An external variable is used when we want to access a variable in more

than one function. In OOP, external variables are not used frequently.


External or global variables are stored on the heap that grows upward in the memory.

Lifetime External variables exist for the life of the program. Memory space is set for them when the program starts and continues in existence until the program ends.

Visibility

An external variable defined at the start of the program listing will be visible to all the functions defined after the external variable.

An external variable that is created but not initialized contains 0. iii) Static Variables

There are two types of static variables, i.e. Static Automatic Variables and Static External Variables.

A static automatic variable has the visibility of a local variable but the lifetime of an external variable. A static automatic variable is visible only inside the function in which it is defined but remains in existence for the life of the program.

Static automatic variables are used when we want a function to remember a value. static keyword is used to create a static automatic variable. A static automatic variable that is created but not initialized contains 0. The initialization of static automatic variables takes place only once, and that is when the first time their function is called.

F-14.cpp #include<iostream.h> #include<conio.h> float getAverage(float); void main(void) { clrscr(); float data=1, average; while(data!=0) { cout<<"Enter a number "; cin>>data; average = getAverage(data); cout<<"New Average is "<<average<<endl; } getch(); } float getAverage(float newdata) { static float total = 0; static int count = 0; count++; total += newdata; return total / count; }

Output Enter a number 5 New Average is 5 Enter a number 15 New Average is 10 Enter a number 25 New Average is 15 Enter a number 35 New Average is 20 Enter a number 10 New Average is 18 Enter a number 20 New Average is 18.333334 Enter a number 30 New Average is 20 Enter a number 0 New Average is 17.5


Returning by Reference As values can be passed by reference, similarly values can be returned by reference. Returning by reference allows us to use a function call on the left side of equal sign, i.e. A function declaration showing returning by reference is:

int& set(void);


Creating a Header File //save this file "line.h" in INCLUDE directory #include<iostream.h> #include<conio.h> void line(void) { for(int a=1;a<=20;a++) cout<<"*"; cout<<endl; } void hello(void) { cout<<"\nHello Hello Hello\n"; } //save this file “header.cpp” #include<iostream.h> #include<conio.h> #include<line.h> void main(void) { clrscr(); line(); hello(); line(); getch(); }

Output ******************** Hello Hello Hello ********************


Arrays Array is a collection of variables of the same data type placed contiguously in memory. The items or elements of array are accessed by index number. Arrays can be used to store basic data types, i.e. int, char and float etc. Arrays can also be used as data members in classes. Array can also be used to hold objects. Arrays can also by used in structures, i.e. we can create an array of variable of structure types and we can use array even inside the structures for defining its members etc.

ARR-1.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int t[7], sum=0; for(int a=0;a<=6;a++) { cout<<"Enter Temperature for day "<<a+1<<" "; cin>>t[a]; sum += t[a]; } for(a=0;a<=6;a++) cout<<"Temperature of day "<<a+1<<" is "<<t[a]<<endl; cout<<"\nAverage temperature is "<<sum/7; getch(); }

ARR-2.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a[5], b[5]; for(int n=0;n<=4;n++) { cout<<"Enter value in element no. "<<n+1<<" "; cin>>a[n]; b[n] = a[n] * a[n]; } cout<<"Array A\tArray B"<<endl; for(n=0;n<=4;n++) cout<<a[n]<<"\t"<<b[n]<<endl; getch(); }

Output Enter Temperature for day 1 34 Enter Temperature for day 2 32 Enter Temperature for day 3 33 Enter Temperature for day 4 35 Enter Temperature for day 5 36 Enter Temperature for day 6 41 Enter Temperature for day 7 32 Temperature of day 1 is 34 Temperature of day 2 is 32 Temperature of day 3 is 33 Temperature of day 4 is 35 Temperature of day 5 is 36 Temperature of day 6 is 41 Temperature of day 7 is 32 Average temperature is 34

Output Enter value in element no. 1 3 Enter value in element no. 2 4 Enter value in element no. 3 5 Enter value in element no. 4 6 Enter value in element no. 5 7 Array A Array B 3 9 4 16 5 25 6 36 7 49


Defining Arrays Like other variables in C/C++, an Array must be defined before it can be used to store information etc. Array definition is:

Array Elements The items in an Array are called elements. (Items of a structure are called members).

The first element of array starts from 0, so an array of 5 elements has index numbers 0 – 4.

Initializing Arrays Arrays can be initialized just as a variable can be initialized at the time of creation. Following example shows an int type of array having 5 elements is initialized.

int age[5] = { 27, 13, 31, 25, 37 };

int age[5];

Data type of Array

Name of Array

Bracket delimit Array size

Size of the Array

Array elements in Memory

Age[0]

Age[1]

Age[2]

Age[3]

Age[4]


Multidimensional Arrays Arrays can be multidimensional. A two dimensional array consists of Rows and Columns as we have them in a matrix. Following example shows multidimensional array created as having 4 Rows and 3 Columns.

int matrix[4][3];

ARR-3.cpp #include<iostream.h> #include<conio.h> const int ROW = 4; const int COLUMN = 3; void main(void) { clrscr(); int matrix[ROW][COLUMN]; for(int a=0;a<ROW;a++) for(int b=0;b<COLUMN;b++) { cout<<"Enter ROW "<<a+1<<" COLUMN "<<b+1<<" "; cin>>matrix[a][b]; } for(a=0;a<ROW;a++) { for(b=0;b<COLUMN;b++) cout<<matrix[a][b]<<"\t"; cout<<endl; } getch(); }

Output Enter ROW 1 COLUMN 1 1 Enter ROW 1 COLUMN 2 2 Enter ROW 1 COLUMN 3 3 Enter ROW 2 COLUMN 1 4 Enter ROW 2 COLUMN 2 5 Enter ROW 2 COLUMN 3 6 Enter ROW 3 COLUMN 1 7 Enter ROW 3 COLUMN 2 8 Enter ROW 3 COLUMN 3 9 Enter ROW 4 COLUMN 1 10 Enter ROW 4 COLUMN 2 11 Enter ROW 4 COLUMN 3 12 1 2 3 4 5 6 7 8 9 10 11 12


Passing Arrays to Functions

Passing Arrays to Functions ARR-4.cpp

#include<iostream.h> #include<conio.h> const int LENGTH=7; void show(int[LENGTH]); void main(void) { clrscr(); int t[LENGTH]; for(int a=0;a<LENGTH;a++) { cout<<"Enter Temperature for day "<<a+1<<" "; cin>>t[a]; } show(t); getch(); } void show(int temperature[LENGTH]) { int s=0; for(int a=0;a<LENGTH;a++) { cout<<"\nTemperature for day "<<a+1<<" is "; cout<<temperature[a]; s += temperature[a]; } cout<<"\nSum of Temperatures is "<<s; cout<<"\nAverage of Temperature is "<<s/LENGTH; }

Output Enter Temperature for day 1 23 Enter Temperature for day 2 24 Enter Temperature for day 3 25 Enter Temperature for day 4 26 Enter Temperature for day 5 27 Enter Temperature for day 6 28 Enter Temperature for day 7 29 Temperature for day 1 is 23 Temperature for day 2 is 24 Temperature for day 3 is 25 Temperature for day 4 is 26 Temperature for day 5 is 27 Temperature for day 6 is 28 Temperature for day 7 is 29 Sum of Temperatures is 182 Average of Temperature is 26


Array of Structures

ARR-5.cpp #include<iostream.h> #include<conio.h> const int LENGTH = 3; struct part { int mn; int pn; float cost; }; void main(void) { clrscr(); part p[LENGTH]; for(int a=0;a<LENGTH;a++) { cout<<"\nItem Number "<<a+1<<endl; cout<<"Enter Model Number ";cin>>p[a].mn; cout<<"Enter Part Number ";cin>>p[a].pn; cout<<"Enter Cost ";cin>>p[a].cost; } clrscr(); for(a=0;a<LENGTH;a++) { cout<<"\nItem Number "<<a+1<<endl; cout<<"\nModel Number "<<p[a].mn; cout<<"\nPart Number "<<p[a].pn; cout<<"\nCost is "<<p[a].cost<<" Rs. "<<endl; } getch(); }

Output Item Number 1 Enter Model Number 10 Enter Part Number 100 Enter Cost 1000 Item Number 2 Enter Model Number 11 Enter Part Number 110 Enter Cost 2000 Item Number 3 Enter Model Number 12 Enter Part Number 120 Enter Cost 3000 Item Number 1 Model Number 10 Part Number 100 Cost is 1000 Rs. Item Number 2 Model Number 11 Part Number 110 Cost is 2000 Rs. Item Number 3 Model Number 12 Part Number 120 Cost is 3000 Rs.


Passing Array into another Array

ARR-6.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a[5], b[5]; for(int x=0;x<5;x++) { cout<<"Enter element no. "<<x+1<<" "; cin>>a[x]; b[x] = a[x]; } cout<<"\nA\tB\n"; for(x=0;x<5;x++) cout<<a[x]<<"\t"<<b[4-x]<<endl; getch(); }

ARR-7.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a[5], l, h; for(int x=0;x<5;x++) { cout<<"Enter element no. "<<x+1<<" "; cin>>a[x]; } l = a[0], h=a[0]; for(x=0;x<5;x++) { if(a[x]<l) l = a[x]; if(a[x]>h) h = a[x]; } for(x=0;x<5;x++) cout<<a[x]<<endl; cout<<"Highest Value entered is "<<h<<endl; cout<<"Lowest value entered is "<<l<<endl; getch(); }

Output Enter element no. 1 1 Enter element no. 2 2 Enter element no. 3 3 Enter element no. 4 4 Enter element no. 5 5 A B 1 5 2 4 3 3 4 2 5 1

Output Enter element no. 1 5 Enter element no. 2 78 Enter element no. 3 3 Enter element no. 4 256 Enter element no. 5 17 5 78 3 256 17 Highest Value entered is 256 Lowest value entered is 3


Objects containing Arrays

ARR-8.cpp #include<iostream.h> #include<conio.h> const int MAX=50; class Stack { private: int st[MAX]; int top; public: Stack() { top = -1; } void push(int var) { st[++top] = var; } int pop() { return st[top--]; } }; void main(void) { clrscr(); Stack s1; s1.push(11); s1.push(22); s1.push(33); s1.push(44); s1.push(55); cout<<"1. "<<s1.pop()<<endl; cout<<"2. "<<s1.pop()<<endl; cout<<"3. "<<s1.pop()<<endl; cout<<"4. "<<s1.pop()<<endl; cout<<"5. "<<s1.pop()<<endl; getch(); }

Output 1. 55 2. 44 3. 33 4. 22 5. 11


Array of Objects

ARR-9.cpp #include<iostream.h> #include<conio.h> const int MAX=10; class Distance { private: int feet; float inches; public: void getDist() { cout<<"\nEnter feet ";cin>>feet; cout<<"\nEnter inches ";cin>>inches; } void showDist() { cout<<feet<<"\'-"<<inches<<"\""; } }; void main(void) { clrscr(); Distance dist[MAX]; int n=0; char ch; cout<<endl; do { cout<<"\nEnter distance number "<<n+1; dist[n++].getDist(); cout<<"Enter another ";cin>>ch; }while(ch!='n'); for(int j=0;j<n;j++) { cout<<"\nDistance number "<<j+1<<" is "; dist[j].showDist(); } getch(); }

Output Enter distance number 1 Enter feet 4 Enter inches 5.5 Enter another y Enter distance number 2 Enter feet 3 Enter inches 5.9 Enter another y Enter distance number 3 Enter feet 6 Enter inches 6.5 Enter another n Distance number 1 is 4'-5.5" Distance number 2 is 3'-5.9" Distance number 3 is 6'-6.5"


Arrays of Characters (Strings)

ARR-10.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); char str[50]; cout<<"Enter a String "; cin>>str; cout<<"You Entered "<<str; getch(); }

Output Enter a String Hello You Entered Hello Enter a String Hello Everyone You Entered Hello Enter a String NationalUniversityOfModernLanguagesH-9IslamabadPakistan You Entered NationalUniversityOfModernLanguagesH-9IslamabadPakistan

Hello\0

.

.

.

.

.

Characters in String

Terminating 0 or null byte

String

String Buffer

str

Unused part of

the buffer


Reading Embedded Blanks

Avoiding Buffer Overflows

ARR-11.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); char str[10]; cout<<"Enter a String "; cin.get(str,10); //get is a member function of cout<<"You Entered "<<str; // the stream class of which getch(); // cin is an object }

Output Enter a String How Are You You Entered How Are Y

ARR-12.cpp #include<iostream.h> #include<iomanip.h> #include<conio.h> const int MAX=10; void main(void) { clrscr(); char str[MAX]; cout<<"Enter a String "; cin>>setw(MAX)>>str; cout<<"You Entered "<<str; getch(); }

Output Enter a String abcdefghijklmnop You Entered abcdefghi


String Constants

Reading Multiple Lines

ARR-13.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); char str[] = "National University of Modern Languages"; // or // char str[] = {'N','a','t', . . . . .}; cout<<str; getch(); }

Output National University of Modern Languages

ARR-14.cpp #include<iostream.h> #include<conio.h> const int MAX=200; void main(void) { clrscr(); char str[MAX]; cout<<"Enter a String "; cin.get(str,MAX,'!'); cout<<"You Entered "<<str; getch(); }

Output Enter a String National University of Modern Languages ! You Entered National University of Modern Languages


Copying a String

ARR-15.cpp #include<iostream.h> #include<conio.h> #include<string.h> const int MAX=10; void main(void) { clrscr(); char name1[MAX], name2[MAX]; cout<<"Enter a String "; cin.get(name1, MAX); strcpy(name2, name1); cout<<"Name 1 = "<<name1<<endl; cout<<"Name 2 = "<<name2<<endl; getch(); }

Output Enter a String NUML Name 1 = NUML Name 2 = NUML


Arrays of Strings

ARR-16.cpp #include<iostream.h> #include<conio.h> const int DAYS = 7; const int LENGTH = 10; void main(void) { clrscr(); char weekdays[DAYS][LENGTH] = {"Friday","Saturday","Sunday","Monday", "Tuesday","Wednesday","Thursday"}; for(int a=0;a<DAYS;a++) cout<<weekdays[a]<<endl; getch(); }

Output Friday Saturday Sunday Monday Tuesday Wednesday Thursday

0

1

2

3

4

5

6

0 1 2 3 3 5 6 7 8 9weekday[0]

weekday[1]

weekday[2]

weekday[3]

weekday[4]

weekday[5]

weekday[6]

F r i d a y

S a t u r d a y

S u n d a y

M o n d a y

T u e s d a y

W e d n e s d a y

T h u r s d a y a a

7

10


Pointers A variable that holds an address value is called a pointer variable or pointer.

Pointers are used for • Accessing Array elements • Passing arguments to a function when the function needs to modify the original

argument • Passing arrays and strings to functions • Obtaining memory from the system

The address stored in a pointer should be of the same type as the pointer, i.e. address of a float variable can not be assigned to a pointer of integer. There is a general purpose pointer that can point to any data type and is called “pointer to void”

P-1.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int v1=11, v2=22,v3=33; cout<<"Value of v1 is "<<v1<<" and address is "<<&v1<<endl; cout<<"Value of v2 is "<<v2<<" and address is "<<&v2<<endl; cout<<"Value of v3 is "<<v3<<" and address is "<<&v3<<endl; getch(); }

P-2.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int v1=11, v2=22; cout<<"Value of v1 is "<<v1<<endl; cout<<"Value of v2 is "<<v2<<endl; cout<<"Address of v1 is "<<&v1<<endl; cout<<"Address of v2 is "<<&v2<<endl; int* p1; //Pointer to Integer p1 = &v1; // Store address of v1 in pointer p1 cout<<"Value of p1 is "<<p1<<endl; p1 = &v2; cout<<"Value of p1 is "<<p1<<endl; getch(); }

Output Value of v1 is 11 and address is 0x8fc3fff4 Value of v2 is 22 and address is 0x8fc3fff2 Value of v3 is 33 and address is 0x8fc3fff0

Output Value of v1 is 11 Value of v2 is 22 Address of v1 is 0x8fc6fff4 Address of v2 is 0x8fc6fff2 Value of p1 is 0x8fc6fff4 Value of p1 is 0x8fc6fff2

Address of operator


P-3.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int v1=11, v2=22; int* p1; p1 = &v1; // Store address of v1 in pointer p1 cout<<"Value of v1 is "<<*p1<<endl; p1 = &v2; cout<<"Value of v2 is "<<*p1<<endl; getch(); }

P-4.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int v1, v2; int* p1; p1 = &v1; *p1 = 10; cout<<"v1 = "<<v1<<endl; v2 = *p1 + *p1 + 5; cout<<"v2 = "<<v2<<endl; getch(); }

P-5.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int i=10; float f=15.27; int* pi; float* pf; void* gp; //”pointer to void”, i.e. general purpose pointer pi = &i; //correct pf = &f; //correct cout<<"\nValue of i is "<<i<<endl; cout<<"address of i is "<<pi<<endl; cout<<"\nvalue of f is "<<f<<endl; cout<<"address of f is "<<pf<<endl; // pi = &f; //incorrect // pf = &i; //incorrect gp = &i; //correct // *gp = *gp * *gp; //incorrect // cout<<"value of gp is "<<*gp<<endl; //incorrect cout<<"\naddress of gp is "<<gp<<endl; gp = &f; //correct // *gp = *gp * *gp; //incorrect // cout<<"value of gp is "<<*gp<<endl; //incorrect cout<<"\naddress of gp is "<<gp<<endl; getch(); }

Output Value of v1 is 11 Value of v2 is 22

Output v1 = 10 v2 = 25

Output Value of i is 10 address of i is 0x8f7efff4 value of f is 15.27 address of f is 0x8f7efff0 address of gp is 0x8f7efff4 address of gp is 0x8f7efff0

When an asterisk is used before a variable name, i.e. *p1, then it is called “Indirection Operator”, i.e. the value of the variable pointed to by. So *p1 represents the value of the variable pointed to by p1.


Pointer to Arrays

P-6.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a[5] = {15,35,24,87,42}; for(int b=0;b<5;b++) cout<<*(a+b)<<endl; getch(); }

P-7.cpp This program sends the address of array to a function that displays the array elements #include<iostream.h> #include<conio.h> void show(int*); void main(void) { clrscr(); int a[5] = {13,21,78,32,64}; show(a); getch(); } void show(int* c) { cout<<"Press any key to display array"<<endl; getch(); for(int b=0;b<5;b++) cout<<*(c+b)<<endl; }

Output 15 35 24 87 42

Output Press any key to display array 13 21 78 32 64

a[0]

a1]

a[2]

a[3]

a[4]

a

*(a+2)

*(a+b) is equivalent to a[b]


Pointer constants and pointer variables

P-8.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); int a[5] = {13,21,78,32,64}; int* p; p = a; //points to a for(int b=0;b<5;b++) cout<<*(p++)<<endl; getch(); }

P-9.cpp Passing Reference as Arguments

#include<iostream.h> #include<conio.h> void square(int&); void main(void) { clrscr(); int v = 5; cout<<"Value is "<<v<<endl; square(v); cout<<"Square is "<<v<<endl; getch(); } void square(int& n) { n*=n; }

P-10.cpp Passing Pointer as Arguments

#include<iostream.h> #include<conio.h> void square(int*); void main(void) { clrscr(); int v = 5; cout<<"Value is "<<v<<endl; square(&v); cout<<"Square is "<<v<<endl; getch(); } void square(int* n) { *n = *n * *n; }

Output 13 21 78 32 64

Output Value is 5 Square is 25

Output Value is 5 Square is 25

Passing variable by reference

Passing pointer as arguments


Pointers and Functions

P-11.cpp #include<iostream.h> #include<conio.h> void cube(int*); void main(void) { clrscr(); int a; cout<<"Enter a Value "; cin>>a; cout<<"Cube of "<<a<<" is "; cube(&a); getch(); } void cube(int* n) { *n = *n * *n * *n; cout<<*n; }

Output Enter a Value 3 Cube of 3 is 27


New and Delete Operator

P-12.cpp #include<iostream.h> #include<conio.h> #include<string.h> void main(void) { clrscr(); char* name="National University of Modern Languages"; int l = strlen(name); char* p; p = new char[l]; strcpy(p,name); cout<<"p = "<<p; delete[] p; getch(); }

Output p = National University of Modern Languages

Returns a pointer that points to a section of memory capable of storing string name

Returns memory to the Operating System that was taken using new operator


Pointers to Objects

P-13.cpp #include<iostream.h> #include<conio.h> class Distance { private: int feet; float inches; public: void getDist() { cout<<"\nEnter feet ";cin>>feet; cout<<"Enter inches ";cin>>inches; } void showDist() { cout<<endl<<feet<<"\'-"<<inches<<"\""<<endl; } }; void main(void) { clrscr(); Distance d1; d1.getDist(); d1.showDist(); Distance* dp; dp = new Distance; dp -> getDist(); // or (*dp).getDist(); dp -> showDist(); getch(); }

Output Enter feet 5 Enter inches 5.5 5'-5.5" Enter feet 6 Enter inches 6.5 6'-6.5"


Passing Array to Functions using Pointer notation

Strings as Function Arguments

P-14.cpp #include<iostream.h> #include<conio.h> void square(int*); void main(void) { clrscr(); int a[5]={0}; for(int n=0;n<5;n++) { cout<<"Enter element no. "<<n+1<<" "; cin>>a[n]; } square(a); for(n=0;n<5;n++) cout<<a[n]<<endl; getch(); } void square(int* v) { for(int i=0;i<5;i++) *v++ *= *v; }

Swapping Through Pointers P-15.cpp

#include<iostream.h> #include<conio.h> void change(int*, int*); void main(void) { clrscr(); int n1=99, n2=11; int n3=22, n4=88; cout<<"Befor Swapping"<<endl; cout<<"n1 = "<<n1<<" n2 = "<<n2<<endl; cout<<"n3 = "<<n3<<" n4 = "<<n4<<endl; change(&n1,&n2); change(&n3,&n4); cout<<"After Swapping"<<endl; cout<<"n1 = "<<n1<<" n2 = "<<n2<<endl; cout<<"n3 = "<<n3<<" n4 = "<<n4<<endl; getch(); } void change(int* s1,int* s2) { int t = *s1; *s1 = *s2; *s2 = t; }

Output Enter element no. 1 3 Enter element no. 2 12 Enter element no. 3 9 Enter element no. 4 3 Enter element no. 5 7 9 144 81 9 49

Output Befor Swapping n1 = 99 n2 = 11 n3 = 22 n4 = 88 After Swapping n1 = 11 n2 = 99 n3 = 88 n4 = 22


Pointers and Strings Pointers to String Constants

P-16.cpp #include<iostream.h> #include<conio.h> void main(void) { clrscr(); char s1[]="NUML"; //Defined as Array char* s2 ="NUML"; //Defined as Pointer cout<<s1<<endl; cout<<s2<<endl; s2++; //Starts pointing to U instead of N in NUML cout<<s2<<endl; getch(); }

Output NUML NUML UML


Strings as Function Arguments

P-17.cpp #include<iostream.h> #include<conio.h> void dispString(char*); void main(void) { clrscr(); char name[]="National University of Modern Languages"; dispString(name); getch(); } void dispString(char* s) { while(*s) //until null character cout<<*s++; //print characters }

Output National University of Modern Languages

Notes of programming

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