Chapter 01: Introduction to Computer Programming

Dr. Anis Koubaa

Apr 19, 20231

CS140: C++ Programming 1

Al-Imam Mohammad Ibn Saud UniversityAl-Imam Mohammad Ibn Saud University

Computer Programming

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Software Instructions to command computer to perform

actions and make decisions Hardware Standardized version of C++

United States American National Standards Institute (ANSI)

Worldwide International Organization for Standardization (ISO)

Structured programming Object-oriented programming

What is a Computer?

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Computer Device capable of performing computations and

making logical decisions Computer programs

Sets of instructions that control computer’s processing of data

Hardware Various devices comprising computer

Keyboard, screen, mouse, disks, memory, CD-ROM, processing units, …

Software Programs that run on computer

C++ Standard Library

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C++ programs Built from pieces called classes and functions

C++ standard library Rich collections of existing classes and functions

“Building block approach” to creating programs “Software reuse”

Basics of a Typical C++ Environment

C++ systems Program-development environment Language C++ Standard Library

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Basics of a Typical C++ Environment

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Phases of C++ Programs:

1. Edit

2. Preprocess

3. Compile

4. Link

5. Load

6. Execute

Loader

PrimaryMemory

Program is created inthe editor and storedon disk.

Preprocessor programprocesses the code.

Loader puts programin memory.

CPU takes eachinstruction andexecutes it, possiblystoring new datavalues as the programexecutes.

Compiler

Compiler createsobject code and storesit on disk.

Linker links the objectcode with the libraries,creates a.out andstores it on disk

PrimaryMemory

Introduction to C++ Programming

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C++ language Facilitates structured and disciplined approach to

computer program design Following several examples

Illustrate many important features of C++ Each analyzed one statement at a time

Structured programming Object-oriented programming

First Program in C++

Printing a Line of Text

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A Basic C++ Program

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1 // Fig. 1.2: fig01_02.cpp

2 // A first program in C++.

3 #include <iostream>

4

5 // function main begins program execution

6 int main()

7 {

8 std::cout << "Welcome to C++!\n";

9

10 return 0; // indicate that program ended successfully

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12 } // end function main

Welcome to C++!

Simple Program: Printing a Line of Text

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Comments Document programs Improve program readability Ignored by compiler Single-line comment

Begin with //

Preprocessor directives Processed by preprocessor before compiling Begin with #

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Basics of a Typical C++ Environment Input/output

cin Standard input stream (like Read) Normally keyboard

cout Standard output stream (like Write) Normally computer screen

cerr Standard error stream Display error messages

A Simple Program: Printing a Line of Text

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Standard output stream object std::cout “Connected” to screen <<

Stream insertion operator Value to right (right operand) inserted into output stream

Namespace std:: specifies using name that belongs to

“namespace” std std:: removed through use of using statements

Escape characters \ Indicates “special” character output

A Simple Program:Printing a Line of Text

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Escape Sequence Description

\n Newline. Position the screen cursor to the beginning of the next line.

\t Horizontal tab. Move the screen cursor to the next tab stop.

\r Carriage return. Position the screen cursor to the beginning of the current line; do not advance to the next line.

\a Alert. Sound the system bell.

\\ Backslash. Used to print a backslash character.

\" Double quote. Used to print a double quote character.

Printing line with multiple statements

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1 // Fig. 1.4: fig01_04.cpp

2 // Printing a line with multiple statements.

3 #include <iostream>

4

5 // function main begins program execution

6 int main()

7 {

8 std::cout << "Welcome ";

9 std::cout << "to C++!\n";

10

11 return 0; // indicate that program ended successfully

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13 } // end function main

Welcome to C++!

Printing multiple lines with a single statement

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1 // Fig. 1.5: fig01_05.cpp

2 // Printing multiple lines with a single statement

3 #include <iostream>

4

5 // function main begins program execution

6 int main()

7 {

8 std::cout << "Welcome\nto\n\nC++!\n";

9

10 return 0; // indicate that program ended successfully

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12 } // end function main

Welcome

to

 

C++!

Using newline characters to print on multiple lines.

Another Simple Program

Adding Integers

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1 // Fig. 1.6: fig01_06.cpp2 // Addition program.3 #include <iostream>4 5 // function main begins program execution6 int main()7 {8 int integer1; // first number to be input by user 9 int integer2; // second number to be input by user 10 int sum; // variable in which sum will be stored11 12 std::cout << "Enter first integer\n"; // prompt13 std::cin >> integer1; // read an integer14 15 std::cout << "Enter second integer\n"; // prompt16 std::cin >> integer2; // read an integer17 18 sum = integer1 + integer2; // assign result to sum19 20 std::cout << "Sum is " << sum << std::endl; // print sum21 22 return 0; // indicate that program ended successfully23 24 } // end function main

Use stream extraction operator with standard input stream to obtain user input.

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Enter first integer45Enter second integer72Sum is 117

Another Simple Program:Adding Two Integers

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Variables Location in memory where value can be stored Common data types

int - integer numbers char - characters double - floating point numbers

Declare variables with name and data type before useint integer1;int integer2;int sum;

Can declare several variables of same type in one declaration Comma-separated listint integer1, integer2, sum;

Another Simple Program:variable and data type

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Variables Variable names

Valid identifier Series of characters (letters, digits, underscores) Cannot begin with digit Case sensitive

boolbool A boolean variable is defined to be of type bool. A boolean has a value of true or false which

correspond to 1 or 0 accordingly.bool correct = true;

bool Yes; correct = false; Yes = true;

Another Simple Program:variable and data type

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CharactersCharacters

A character variable is defined to be of type char.

A character variable occupies a single byte which contains the code for

the character. This code is a numeric value and depends on the character

coding system being used .

e.g. character A has the ASCII code 65

the character a has the ASCII code 97.

A literal character is written by enclosing the character between a pair of

single quotes (e.g., 'A').

char ch = 'A';

a character variable may be specified to be signed (by default on most

systems) or unsigned.

signed character : -128 through 127

unsigned character : 0 through 255

Another Simple Program:variable and data type

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Integer:Integer: An integer variable may be defined to be of

type: short,

int, or long.

The only difference is that an int uses more or at least the same number of bytes as a short, and a long uses more or at least the same number of bytes as an int (i.e. a short may uses 2 bytes, an int also 2 bytes, and a long 4 bytes.)

short int age = 20;int salary = 65000;long int price = 4500000;

Another Simple Program:variable and data type

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Integer:Integer: By default, an integer variable is assumed to

be signed (i.e., has positive as well as negative values).

An integer can be defined to be unsigned as

well as signed type

unsigned short int age = 20;unsigned int salary = 65000;unsigned long int price = 4500000;

Another Simple Program:variable and data type

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Real Numbers A real variable may be: float or double. The difference is in the number of bytes which therefore

offers a greater range and accuracy for representing real numbers (e.g.; a float may uses 4 bytes and a double may uses 8 bytes).

float interestRate = 0.06; double pi = 3.141592654;

In addition to the decimal notation used so far, literal reals

may also be expressed in scientific notation. For example,

0.002164 may be written in the scientific notation as:

2.164E-3 or 2.164e-3

Which is interpreted as follows: 2.164E-3 = 2.164 × 10-3

Input methods

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Input methods Input stream object

>> (stream extraction operator) Used with std::cin Waits for user to input value, then press Enter (Return)

key Stores value in variable to right of operator

Converts value to variable data type

= (assignment operator) Assigns value to variable Binary operator (two operands) Example:

sum = variable1 + variable2;

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What happens in the memory?

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Memory Concepts

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Variable names Correspond to actual locations in computer's

memory Every variable has name, type, size and value When new value placed into variable, overwrites

previous value Reading variables from memory nondestructive

Memory Concepts

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std::cin >> integer1; Assume user entered 45

std::cin >> integer2; Assume user entered 72

sum = integer1 + integer2;

integer1 45

integer1 45

integer2 72

integer1 45

integer2 72

sum 117

Arithmetic

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Arithmetic calculations *

Multiplication /

Division Integer division truncates remainder

7 / 5 evaluates to 1

% Modulus operator returns remainder

7 % 5 evaluates to 2

Arithmetic

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Rules of operator precedence Operators in parentheses evaluated first

Nested/embedded parentheses Operators in innermost pair first

Multiplication, division, modulus applied first Operators applied from left to right

Addition, subtraction applied last Operators applied from left to right

Operator(s) Operation(s) Order of evaluation (precedence)

() Parentheses Evaluated first. If the parentheses are nested, the expression in the innermost pair is evaluated first. If there are several pairs of parentheses “on the same level” (i.e., not nested), they are evaluated left to right.

*, /, or % Multiplication Division Modulus

Evaluated second. If there are several, they re evaluated left to right.

+ or - Addition Subtraction

Evaluated last. If there are several, they are evaluated left to right.

Decision Making: Equality and Relational Operators

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if structure Make decision based on truth or falsity of

condition If condition met, body executed Else, body not executed

Equality and relational operators Equality operators

Same level of precedence Relational operators

Same level of precedence Associate left to right

Decision Making: Equality and Relational Operators

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Standard algebraic equality operator or relational operator

C++ equality or relational operator

Example of C++ condition

Meaning of C++ condition

Relational operators

> > x > y x is greater than y

< < x < y x is less than y

>= x >= y x is greater than or equal to y

<= x <= y x is less than or equal to y

Equality operators

= == x == y x is equal to y

!= x != y x is not equal to y

Decision Making: Equality and Relational Operators

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using namespace std; Eliminate use of std:: prefix Write cout instead of std::cout

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1 // Fig. 1.14: fig01_14.cpp2 // Using if statements, relational3 // operators, and equality operators.4 #include <iostream>5 6 using std::cout; // program uses cout7 using std::cin; // program uses cin 8 using std::endl; // program uses endl 10 // function main begins program execution11 int main()12 {13 int num1; // first number to be read from user14 int num2; // second number to be read from user15 16 cout << "Enter two integers, and I will tell you\n"17 << "the relationships they satisfy: ";18 cin >> num1 >> num2; // read two integers19 20 if ( num1 == num2 ) 21 cout << num1 << " is equal to " << num2 << endl;22 23 if ( num1 != num2 )24 cout << num1 << " is not equal to " << num2 << endl;25

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26 if ( num1 < num2 )27 cout << num1 << " is less than " << num2 << endl;28 29 if ( num1 > num2 )30 cout << num1 << " is greater than " << num2 << endl;31 32 if ( num1 <= num2 )33 cout << num1 << " is less than or equal to "34 << num2 << endl;35 36 if ( num1 >= num2 )37 cout << num1 << " is greater than or equal to "38 << num2 << endl;39 40 return 0; // indicate that program ended successfully41 42 } // end function main

Enter two integers, and I will tell you

the relationships they satisfy: 22 12

22 is not equal to 12

22 is greater than 12

22 is greater than or equal to 12

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Enter two integers, and I will tell you the relationships they satisfy: 7 7 7 is equal to 7 7 is less than or equal to 7 7 is greater than or equal to 7

Exercise

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Write a program which reads 4 numbers and print the biggest and the lowest numbers