UNIT-II(c programming)

7/30/2019 UNIT-II(c programming)

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UNIT-II

Dennis Ritchie


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1.History of c language

ALGOL

BCPL

B

C


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History of c language

project multics to develop an operating system.1969, language B was developed by Ken

Thompson.

c was develop in 1972 by Dennis M. Ritchieat Bell Labs(AT&T) in USA.

1988 c language was standardized by ANSI as

ANSI CANSI- American National Standards Institute.


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2. Features of C language1. Robust rich set of built in functions and operators can be used to write

any complex programs.

2. C compilers combines the capabilities of low level languages withfeatures of high level language. Therefore it is suitable for writing thesystem softwar5. e, application software and most of the compilers ofother languages also developed with c language.

3. Efficient and fast- rich variety of data types and powerful operators.

4. Portable- c program written on one computer can also run on the othercomputer with small or no modification.

ex- c program written in windows can also run on the linux operatingsystem.

5. Structured programming- every program in c language is divided into

small module or functions so that it makes the program much simpleand debugging, maintenance of the program is easy.

6. Ability to extend itself- A C program is basically a collection of variousfunction supported by C library (also known as header files). We can alsoadd our own functions to the C library. These functions can be reused inother applications or programs by passing pieces of information to the

functions, you can create useful, reusable code.


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3. Structure of c program


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Include

information

about standard

library

Main calls library

function printf to

print this message.


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C program consists of functions and variables.

Function contains the statements that specify

computation operation to be done.

Variables stores the values used during thecomputation.

Function can be named whatever you like. However,

main is the special function where the programexecution starts. Very program must have a main

some where.


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Preprocessor commands

The preprocessor command always starts withsymbol #

#include this is called preprocessorcommand.

Include command tells the preprocessor that we needthe information from selected libraries called headerfile.

Header file- collection of library files.

-> it tells the compiler to include the information aboutthe standard input\ output library.

-> every program must need at least one libraryfunctions which are available in the header file.


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Global variables.

The variables which are declared at the starting

of the program called global variable.

They are visible to all the parts of the program.


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C program consists of functions and variables.

Function contains the statements that specify

computation operation to be done.

Variables stores the values used during thecomputation.

Function can be named whatever you like. However,main is the special function where the programexecution starts. Very program must have a mainsome where.

Functions are communicate each other by passinglist of values called arguments.

Main is defined to be a function that expects noarguments.


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Local variables

The variables which are declared in a function

are called local variables to that function.

These variables visible only within the

function.


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Local variables

The variables which are declared in a function

are called local variables to that function.

These variables visible only within the

function.


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All the statements of main are enclosed in braces.

A function can be called by naming it, followed by aparanthesized list of arguments.

Main calls the printf with argument hello world\n.

The string \n in the string is C notation for thenewline character, which when printed advances theoutput to the left margin on next line.

Printf(hello world\n);


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printf(hello world

);

C compiler prints the error message.

same program can also rewrite as

#includemain()

{

printf(hello);

printf(world);printf(\n);

return 0;

}


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Main function may return some integer value to the

operating system

So at the end of the main add the statement return0.

main() is same as the int main()- it means that the

function main returns some integer value to the os. Otherwise write the main as void main()- it does not

return any value to the operating system and not

necessary to write the return statement.

Each statement in c program must end with (;)

specifies that the instruction is ended.


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Comments

To make the program more readable use the

comments.

They may used to make the program easier to

understand.

Two types of comments

1. block comment

2. line comment.


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1. Block comment

/* write a program for the addition of two integernumbers*/

#include

main()

{

int a=10,b=20,c;

c=a+b;

printf(sum of a and b=%d,c);return 0;

}


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1. Block comment

above two lines

/* write a program for the addition of two integer

numbers*/

are a comment, which explains what the program does.

Any characters between /* and */ are ignored by thecompiler.

Comments may appear anywhere a blank or tab or

newline. /* and */ is used to comment the multiple lines of

code which ignored by the compiler.

/*/*..*/ - nested block comments are invalid.


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2. Line comment

It uses two slashes // .

This is used to comment single line.

// #include


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Character set

Characters are used to form words, numbers

and expressions.

Characters are categorized as

1.Letters

2.Digits

3.Special characters4.White spaces.


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Character set Letters (upper case and lower case)A B C D E F G H I J K L MN O P Q R S T U V W X Y Za b c d e f g h i j k l mn o p q r s t u v w x y z

Digits0 1 2 3 4 5 6 7 8 9

Special Characters " ( ) * + - / : =

! & $ ; < > % ? , . # @ { } [ ]\ | White spacesblank space

horizontal spaceCarriage return, new line.


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Key words and identifiers

C word is classified as either keywords oridentifiers.

Keywords have fixed meanings these

meanings cannot be changed Keywords must be in lowercase.

Keywords depends on compilers that must be

identified from the c manuals.


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Key words

C key words

auto break case char const

continue default do double else

enum extern float for goto

if int long register return

short signed sizeof static struct

switch typedef union unsigned void

volatile while


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identifiers

Identifiers are name of the variables and

functions.

Identifiers are user defined names means

name given to the variable whatever user

likes.

Ex- int a;// a is identifier

int sum;// sum is identifier.


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variables

When you want to process some information, you can save

the values temporarily in variables.

Program

#include

main()

{int a=10,b=20,c;

c=a+b;

printf(sum of a and b=%d\n,c);

return 0;

}

o/p- sum of a and b=30

Definition- variable which stores the value in the memory location, that value varies

during program execution

variables in the above program are a b and c .

Notevariables must

be declared before they

are used, usually at the

beginning of the

function.


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Variables names There are some restrictions on the variable names

1. Names are made up of letters and digits andunderscore(_).

2. The first character of the name must be a letter

3. The underscore is also a legal first character, but itsuse is not recommended.

4. Upper case and lower case letters are distinct, so a

and A are two different names.

5. C keywords can't be used as variable names

6. White space is not allowed in variable names.


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The following list contains some examples of

legal and illegal C variable names:

Variable Name LegalityPercent Legal

y2x5__fg7h Legal

annual_profit Legal

_1990_tax Legal but not advised

savings#account Illegal: Contains the illegal character #

double Illegal: Is a C keyword

9winter Illegal: First character is a digit


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Data types in C Type specifies a set of values and a set of operations

that can be applied on those values.

The data type defines the amount of storage allocated

to variables, the type of values stored in variables.

There are only a few basic data types in c

char a single byte, capable of holding one character in

the local character set

intan integer, typically reflecting the natural size of

integers on the host machine float single-precision floating point

double double-precision floating point


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There are number of qualifiers that can be applied to the basic

types

The qualifiers are also used to increase the range of the values.

Qualifiers are signed, unsigned, short and long.

Signed, unsigned are applied to char and integers.

short apply to integers.

long is used for integers and double.

unsigned numbers are always positive or zero, and obey the 2n,

signed numbers are

short int a;

long int b;

the word int can omitted


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The charData Type

The shortest data type is character.

It is stored in 1 byte in memory.

Corresponding integer values for all characters are defined in ASCII

code (American Standard Code for Information Interchange).

For example:

character constant ahas an int value 97, b - 98, A- 65 etc.

The keywordchar is used to declare a variable of a character type.

char letter =A;

char letter = 65;


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The int Data Type

An integer number (also called whole number) has no fractional part or

decimal point.

-> The keyword int is used to specify an integer variable.

-> it occupies 2 bytes (16 bits) or 4 bytes (32 bits), depending on themachine architecture.

16-bit integer can have values in the range of

- 32768to

32767

One bit is used for sign.

For 32-bit integer the range is about from -2 to +2 billions

The sizes of the data types are machine dependent


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The sizes of the data types are machine dependent.

Short is 16bits, long 32 bits and int either 16 bits or

32 bits.

These sizes are chosen by the compiler for its ownhardware.

In 16 bit processor short2, int- 2, long- 4

In 32 bit processor short-2, int -4, long-4. They are restricted that short is no longer than int, int

is at least 16 bits , long is at least 32 bits.

Unsigned integer


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Unsigned integer

If you know that the variable cannot have negative values, you may

declare it as unsigned.

unsignedvariable type occupies the same amount of computer memoryas int but the actual value can be twice as large as the maximum

available int, because all values are positive.

To decrease the size of allocated memory for a variable which is not too

large, you may use theshort type which is stored in 2 bytesThefloatData Type

-> The data typefloat represents a floating point number (also called a

real number or numbers with decimal ).->The keywordfloat is used to declare a variable of the type float.

Ex: float float_num1=1.34;

-> The float type variable is usually stored in 4 bytes, which means it is

at least 6 digits of precision.


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ThedoubleData Type

A floating point number can also be represented by thedouble data type.

The data type double is stored on most machines in 8 bytes which is

about 15 decimal places of accuracy.To declare a variable of the type double, use the keyworddouble.

Types in C


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Types in C

typesize

(byte)

smallest

number

largest

numberprecision constant

format

specifier

long double 10 3.4E - 4932 1.1E+4932 1.08E - 191.2345L,

1.234E - 5L%Lf, %Le, %Lg

double 8 1.7E - 308 1.7E+308 2.22E - 161.2345,

1.234E - 5%lf, %le, %lg

float 4 1.7E -38 3.4E+38 1.19E - 71.2345F,

1.234E - 5F%f, %e, %g

unsigned long 4 0 4294967295 123UL %lu

long 4 - 2147483648 2147483647 123L %ld, %li

unsigned 4 0 4294967295 123U %u

int 4 - 2147483648 2147483647 123 %d, %i

unsigned short 2 0 65535 123U %hu

short 2 - 32768 32767 123 %hd, %hi

unsigned char 1 0 255 a, 123, \n %c

char 1 - 127 or 0 127 or 255 a, 123, \n %c-128 127


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Formatted input/ output

The data is to be arranged in a particular format. The data is input to and out put from a stream.

A stream is a source or destination of the data. it isassociated with a physical device, such as terminals

(keyboard, monitor). C has two forms of streams- text stream and binary

stream.

Text stream consists of sequence of characters.

Binary stream consists of a sequence of data in 0sand 1s.


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FIGURE Stream Physical Devices


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The data is formatted using the printf andscanf functions.

Scanf() converts the text stream coming from

the keyboard to data values (char, int,ect) andstores them in the program variables.

Printf() converts the data stored in variablesinto the text stream for output the keyboard.


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IGURE Output Formatting Concept

printf() takes the set of data values and converts them to text stream using

formatting instructions contained in a format control string.

Fomat control specifiers are used to format the text stream.


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Format specifier specifies the data values type, sizeand display position.

Printf statement takes two arguments

1. control string and 2.data values( variables)

Control string contains the format specifiers andsome text.

syntaxprintf(control string,var1,var2,..varn);

Ex-

int a=10, b=20;

printf(a=%d b=%d, a,b);


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URE Output Stream Formatting Example


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URE Formatting Text from an Input Stream

scanf(control string,&var1,&var2.. &varn);

control string includes format specifiers and specifies the field width.


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int a=12,b=23145;

scanf(%2d %5d,&a,&b);

V i bl d l i


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Variable declaration Each variable must be declared and defined before

used in the program.

Variable declaration-

1. tells the compiler what is the name of the variable.

2. specifies what type of data values the variable can

hold.

variable definition- reserves the memory for the

declared variable and store some value is called

garbage value.-> variable declaration and variable definition done at the same

time.


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int a;Variable declaration and definition

23456

a

1000

Variable name

Garbage value

Address of the variable


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Variable initialization

While declaring the variable assign initial

value is called variable initialization.

Data type identifier= initial value;

ex int a=10;

float b=2.1;float pi=3.14;

char ch=A;


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constants Constants- fixed values those cannot be

changed during the program execution.

Several types of constants are used

1.Character constants

1.1 single character constants

1.2 string constants.

2. Numeric constants.2.1 integer constant

2.2 real constants.


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Type qualifier const

One way to use the constant is with memory

constants. Memory constants use a c type

qualifier; const.

This indicates that the data cannot be

changed.

const type identifier= value;

const float pi=3.14;


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Ex-#include

void main()

{

float area,radius=3.0;

const float pi=3.14;

area=pi*radius*radius;

printf(area of a circle= %f,area);}


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1. Character constants

A single character constants are enclosed in

single quotes.

Ex- 1 X %

Character constants have integer values called

ASCII values.

char ch=A;

printf(%d,ch); ->65

similarly printf(%c,65)-> A


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String constants- string a collection of

characters or sequence of characters enclosed

in double quotes.

The characters may be letters, numbers,special characters and blank space.

Ex- snist

2011

A.

Backslash \escape characters


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Backslash \escape characters Backslash characters are used in output functions.

These backslash characters are preceded with the \ symbol.

Constant meaning

\a Alert(bell)

\b Back space

\f Form feed

\n New line

\r Carriage return

\v Vertical tab

\t Horizontal tab

\ Single quote

\ Double quotes

\? Question mark

\\ Backslash

\0 null


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Numeric constants

1. integer constant- sequence of digits like

0to 9.

Ex- 123 -678 0 +78.

Rules

1. Integer constant have at least one digit

2. No decimal points

3. No commas or blanks are allowed.4. The allowable range for integer constant is

-32768 to 32767.


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To store the larger integer constants on 16 bit machine

use the qualifiers such as U,L,UL.

Type Representation Value

int +245 245

int -678 678

unsigned integer 65342u/65342U 65342

unsigned long int 99999UL 99999

long integer 999999L 999999


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2. Real constants- the numbers containing

fractional parts like 3.14.

1.9099 -0.89 +3.14

Real constants are also expressed in

exponential notation.

Mantissa e exponent

The part appearing before e is called mantissa this may

be the fractional number or integer number and part following e is called

exponent .

Ex 215.65 may be written as 2.1565e2.


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Examples of real constants

Type Representation Value

double 0. 0.0

double 0.0 .0

float -2.0f -2.0

long double 3.14159276544L 3.14159276544


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#include

void main()

{

const int a=10;int b=20;

a=a+1;

b=b+1;

printf(a=%d b=%d,a,b);

}

operators


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operators

C language is robust because it has rich set of

operators. Operatora symbol used to perform a

mathematical or logical manipulations.

Operands- data values\variables are called

operands.

Operators must be applied on the operands.

Expression- combination of operands and operators,

which evaluated to one value i.e either true or false..

X=Y+Z

expression

Operands- x,y,z

Operators- =, +


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Types of operators

Following are the c operators.1.Arithmetic operators

2.Relational operators.

3.Logical operators.4.Assignment operators.

5.Increment and decrement operators.

6.Conditional operators.7.Bitwise operators.

8.Special operators.

1 Arithmetic operators


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1. Arithmetic operators

Arithmeticoperators

Meaning

+ Addition or unary operator

- Subtraction or unary operator

* Multiplication

/ Division- gives only coefficient.

% Modulo division- givesremainder.

c= a+b;

z= x-y;

2.Relational operators.


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p

Relational operators are used to compare the

relationship between two operands.

Relationaloperators

Meaning

< Is less than> Is greater than

= Greater than or equal to

= = Equal to

!= Not equal to

The value of a relational

Expression is either one or

zero. It is one if the

Specified relation is true and

zero if the relation is false .

Relational operators are used

if and else, while, for

statements.

3 Logical operators


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3. Logical operators. Logical operators used to test more than one

condition and make decision. Yields a value either one or zero

Logicaloperator

meaning

&& Logical AND

|| Logical OR

! Logical NOT

Ex- x


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AND OR truth table

Op1 Op2 AND OR

0 0 0 0

0 1 0 1

1 0 0 1

1 1 1 1

4. Assignment operators


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g p

The value of an expression assigned to a

variable.

Assignment operator is =

variable = expression;

a= a+1; =>a+=1;

x= x-1; => x-=1;

x=x*(y-1); =>x*=y-1;

x=x/(y-1); => x/=y-1; x=x%y; =>x%=y;

5 Increment and decrement operators


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5. Increment and decrement operators.

Increment operator- ++

Decrement operator - --

++- add one(1) value to the operand

-- - subtracts one value to the operand.

++x; equal to x=x+1;or x+=1;

--y; equal to y=y-1;or y-=1;

6 Conditional operators ?:


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6. Conditional operators ?:

Another name is ternary operator

Syntax

Exp1?exp2:exp3;

where exp1, exp2,exp3 are expressions.

Exp1 evaluated first if it is non zero (true), then the exp2 is evaluate

and becomes the value of the expression.

if exp1 is zero(0), then exp3 is evaluated and become the value of

the expression.

?:

ex- a=1;

b=2;

x= (a


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p

Manipulates the data which is in binary form.

Bitwise

operators

Meaning

& Bitwise AND

| Bitwise OR

^ Exclusive OR

> Shift right

~ Ones compliment


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/Examples:& Bitwise AND 0110 & 0011 0010

| Bitwise OR 0110 | 0011 0111

^ Bitwise XOR 0110 ^ 0011 0101

Right shift 01101110 >> 3 00001101

~ One's complement ~0011 1100

Notice: > multiply/divide by 2n

Don't confuse bitwise & | with logical && ||


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8. Special operators

Special operators- *, -> ., , sizeof()Sizeof()- unary operator (operates on a single value)

Produces a result that represent the size in bytes or the data specified

Format

sizeofdata

e.g.

int a = 5;

sizeof(a);//produces 4

Orsizeof(data type)

e.g. sizeof(char);//produces 1


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Unary operators- operators used on a single

operand - -, +, ++, --.

Binary operators - operators used to apply in

between two operands- +, -, /, %.


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FIGURE Expression Categories

Primary expression


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Primary expression

An expression as only one operand no

operator is called primary expression. It may be name of the variable, constant, or a

parenthesized expression.

a, snist,1.56, (x=10*2).

Post fix expression- expression containsoperand followed by one operator.

ex- a++; a- -;Operand must be the variable in post fix expression.


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FIGURE Result of Postfix a++

expression

1. Value of the variable a is assigned to x

2. Value of the a is incremented by 1.


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Example on post fix expression

#includevoid main()

{

a=10;

x=a++;

printf(x=%d, a=%d,x,a);

}

out put- x=10, a=11


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FIGURE Prefix Expression

Prefix expression- operator followed by the operand.

ex- ++a;


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FIGURE Result of Prefix ++a


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Example on pre fix expression

#includevoid main()

{

a=10;

x=++a;

printf(x=%d, a=%d,x,a);

}

out put- x=11, a=11


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FIGURE Unary Expressions

Unary expression- unary operator followed by the operand


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Table Examples of Unary Plus And Minus Expressions


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FIGURE Binary Expressions

Binary expressions- operator must be placed in between the

two operands.

1Operand must be integral data type( int, float)

Ex- a+ba-c

Precedence and association rules among


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operators Precedence- the order in which expression is

evaluated.

Every operator has a special precedence.

The operators which has higher precedence in the

expression is evaluated first. example- a=8+4*2; a=?

Associativity- Operators on the same line in the chart

have the same precedence, and the "Associativity"column on the right gives their evaluation order.

Operator Precedence ChartOperator Type Operator Associativity


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Primary Expression Operators () [] . -> expr++ expr-- left-to-right

Unary Operators * & + - ! ~ ++expr --expr (typecast) sizeof right-to-left

Binary Operators * / % left-to-right

+ -

>> =

== !=

&

^

|

&&

||

Ternary Operator ?: right-to-left

Assignment Operators = += -= *= /= %= >>=


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83

FIGURE 3-8 Left-to-Right Associativity

Implicit Conversion

Type conversion- converting from one data type to another data type


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Implicit Conversion

If the compiler expects one type at a position, but another type is provided, thenimplicit conversion occurs. Compiler itself converts one type to other.

Conversion during assignments:

char c = 'a';

int i;

i = c; /* i is assigned by the ascii of a */

Arithmetic conversionif two operands of a binary operator are not the sametype, implicit conversion occurs:

int i = 5 , j = 1;float x = 1.0, y;

y = x / i; /* y = 1.0 / 5.0 */

y = j / i; /* y = 1 / 5 so y = 0 */

You can override Cs default conversions by specifying your own temporary type

change using the format:

(data type) expression

(data type) can be any valid C data type and expression is any variable, constant or

a combination of both

int x;

x=(int)7.5;

Explicit Conversion or type casting

Decision control structures


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Decision control structuresTill now we have used sequence control structure in the programs, in which the various

steps are executed sequentially i.e. in the same order in which they appear in the

program.In C programming the instructions are executed sequentially, by default.

At times, we need a set of instructions to be executed in one situation and an another

set of instructions to be executed in another situation.

In such cases we have to use decision control instructions.This can beacheived in C using;

(a)The if statement

(b)The if-else statement

(c)The conditional operators

1 If


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1. If statement

Based on the condition execute the set ofinstructions otherwise skip them.

C uses the key word if to implement the

decision control instruction. general form of if statement

if( condition\expression)

{

execute the statements;

}

Condition following the

if must be enclosed within

parenthesis.If the condition is true then

execute the given statement

otherwise the statements not

executed.

If


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If statement

If it has single statement to execute then curlybraces are optional.

More than one statement curly braces are

compulsory.

Ex- int rno=2408;

if(rno==2408)

printf(this is ECE-C2);

f condition


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condition

statement

statement

if ( condition )

statement;

Enter

Test

Body of the IF Statement

Exit

If l


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If- else statements

if statement will execute a single statement, or a group ofstatements, when the expression following if evaluates to true.But it does nothing when the expression evaluates to false.

In case, we want to execute one group of statements if theexpression evaluates to true and another group of statements ifthe expression evaluates to false, we need to use the If-elsestatement.

The syntax of If-else statement is as follows;if (condition\expression){

Statement1}

else {

statement2 }

statement-x

The expression evaluated to true,statement1 is executed.

If false, statement2 is executed.

Both cases statement-x is executed

The if-else StatementAn else clausecan be added to an if statement to make an if-else


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statement

If the condition is true, statement1 is executed; if the condition isfalse, statement2 is executed

One or the other will be executed, but not both

Enter

Test

Body of the

IF Statement1

Exit

Body of the

ELSE Statement2

Flowchart for if-else


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Examplefloat percentage;

printf (enter the percentage);

scanf (%f, &percentage);

if (percentage


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Few points to remember

else must be written exactly below the if

If there is only one statement in if and else

block we can drop the pair of curly braces.

if( x>0)

if(a>b)

z=a;else

z=b;

if( x>0)

{

if(a>b)

z=a;

}

else

z=b;

Nested if else- within the if else we caninclude other if-else either in if block or


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else block

TF

TF

Nested if- else


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Marks obtained by the student must given through

keyboard. Print the result as per the following

rules.

1. Percentage is above or equal to 75- distinction.

2. Percentage is less than 75 and equal to 60- first

class.3. Percentage is less than 60 and equal to 50- second

class.

4. Percentage is less than 50 and equal to 40- thirdclass.

5. Percentage is below 40 failed.

#includevoid main()

{

float m1 m2 m3 m4;


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float m1,m2,m3,m4;

float perc;

printf(enter marks\n);

scanf(%f%f%f%f,&m1,&m2,

&m3,&m4);

perc=(m1+m2+m3+m4)/4;

if(perc>=75)

printf(\ndistinction);

else

{

if(per=60)

printf(\n first class);

else{if(per=50)

printf(\n second class);

else {

if(per=40)

printf(\n third class);

else

printf(\nfail);

}//else

}//else

}//else

Disadvantages-

care must be taken to match thecorresponding pair of braces.

Else if statement


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if(expression1)

statement-1;else if(expression-2)

statement-2;

else if(expression-3)

statement-3;else if (expression-n)

statement-n;

else

statement-x;statement-y

Draw the flowchart for the else if statement.

else if clauseNested if else


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#include

void main()

{

float m1,m2,m3,m4;float perc;



&m3,&m4);

perc=(m1+m2+m3+m4)/4;

if(perc>=75)

printf(\ndistinction);

else

{

if(per=60)


else{

if(per=50)


else {if(per=40)


else

printf(\nfail);

}//else

}//else

}//else

#include

void main()

{

float m1,m2,m3,m4;float perc;



&m3,&m4);

perc=(m1+m2+m3+m4)/4;

if(perc>=75)printf(\ndistinction);

else if(per=60)


else if(per=50)


else if(per=40)


else

printf(\nfail);

Nested if else

Switch statement


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Switch statement

In else if statement as the no of choiceincreases the program becomes difficult to

read.

C has a built in multi way decision statementcall it as switch.

The control statement that allows us to make

a decision from the number of choices iscalled switch.

Switch statement


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General form of switchswitch (expression)

{case value-1:

block1;

break;

case value-2:

block2;break;

case value-n:

blockn;

break;

default:

default block;

}//switch

statement-x;

1. The expression is any expression

that must evaluates to integer value.

2. The keyword case followed by aninteger or a character constant.

3. Each value in each case must be

different from all the others.

4. How this program runs? First

expression is evaluated.5. This evaluated value compares

against the values that follow the

case statements.

6. When a match is found, executes the

statements following that case andall the other cases were skipped.

7. If no match is found with any of the

case statements, default block is executed.

8. Default is optional.

9. At last statementx is executed.Break is used to exit from block

Examples on switch


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Void main()

{

int a;scanf(%d,&a);

switch(a)

{

case 1:

printf(One);break;

case 2:

printf(two);

break;

case 3:

printf(three);break;

default:

printf(this is default);

}//switch

}//main

Void main()

{

int a;scanf(%d,&a);

switch(a)

{

case 1:

printf(One);

case 2:printf(two);

case 3:

printf(three);

default:

printf(this is default);}//switch

}//main

Note- there is no break in default case.

Tips about the usage of switch

case al es ma not be in the ascending order We can p t the


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case values may not be in the ascending order. We can put the

cases in any order.

int a;

scanf(%d,&a);

switch(a)

{

case 3:

printf(One);

break;

case 1:printf(two);

break;

case 2:

printf(three);

break;

default:

printf(this is default);

}//switch

we can also use char values in case and switch.


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char ch=x;

switch(ch)

{case A:

printf(this is A);

break;

case x:

printf ( this is small x);

break;

default: printf (other letter);

}//switch

ch expression evaluated to the asciivalue of x it is also an integer value

can also execute a common set of statements for multiple


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cases.

ex- write a program to test whether the given alphabet is vowel

or consonant.Void main(){ char ch;

printf( enter the alphabet);

scanf(%c,&ch);

switch(ch)

{case a:

case e:

case i:

case o:

case u:printf (\nthe alphabet is vowel);

break;

default:

printf(\nthe alphabet is consonant);

}

if there are multiple statements to be executed in the case noneed to enclose them in pair of curly braces.


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Every statement in the switch must belong to some case or

other. Even if a statement does not belong to any other case the

compiler doesnt give any error. However that statement neverexecuted.

Ex-

switch(x)

{

printf(\nhai);case 1:

printf(one);

break;

}//switch if no default case, the compiler executes the statement immediately

following the close brace of switch

switch may occur within another switch called


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nested switch.

continue statement should not used in switch.

Switch statement is mainly used for the menu drivenprograms.

value in the case must be an int constant or char

constant or an expression that evaluates to one ofthese constants. even float is not allowed.void main()

{ int x;

scanf("%d",&x);

switch(x)

{ case (x


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/*An institution gives grades to its students as follows:

a. Grade A if he gets 80 or more marks

b. Grade B if he gets between 60 and 79(both inclusive)

c. Grade C if he gets between 50 and 59(both inclusive)d. Grade D if he gets between 40 and 49(both inclusive)

e. Grade F otherwise.*/

void main()

{

float perc;int index;

clrscr();

printf("\nenter the percentage marks");

scanf("%f",&perc);

index=perc/10;

switch(index){

case 10:

case 9:

case 8:

printf("\n grade A");

break;

case 7:

case 6:

printf("\n grade B");break;

case 5:

printf("\ngrade C");

break;

case 4:

printf("\ngrade D");break;

default:

printf("\n grade F");

}//switch

Repetitive control structures

P ll t f t f i t ti


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Program allows to perform a set of instructions

repeatedly until a particular condition is being

satisfied.

This is called repetitive control structures or

loop control structures.

Loop control structures are:

1. while statement

2. do- while statement3. for statement

Loops in C

While loop


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Set of instructions to be executed repeatedly

until the condition is satisfied.

ex- print the integer numbers from 1 to 10.

Compound statements

while( expression)

{

Statements

}

Syntax for while

Single statementwhile( expression)

Statement

While statement


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The statement (or a block of statements) is executed

repetitively until the condition becomes false.

while ( condition )

statement;

while is a

reserved word If the condition is true, the

statement is executed.

Then the condition is

evaluated again.

The expression may be relational or logical expression.

The statements in the loop may be single or block of statements. If single

->while(i


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p y g g

the curly braces are optional.

The expression must be eventually become false, otherwise the loop would

be executed forever, indefinitely.

int i=1;

while(i


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float a=1.0;

while(a loop goes into infinite loop.

Write a c program to find the sum of the first n naturalnumbers


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While example

#include

void main(void){

int n,i = 1, sum = 0;

printf(\nenter n value);

scanf(%d,&n);while ( i


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Statements in the loop are executed

first (at least once, and condition istested last

Loop is controlled by a condition orcounter

Syntax

do {

statement;

statement;

} while (condition);statement;

Write a c program to find the sum of the first n naturalnumbers


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While example

#include

void main(void){

int n,i = 1, sum = 0;


scanf(%d,&n);while ( i


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for (expr1; expr2; expr3)

statement;

expr1 controls the looping action,

expr2 represents a condition that

ensures loop continuation, expr3

modifies the value of the control

variable initially assigned by expr1

When a for statement is executed for first time i=1 is initialized.

Next expr2 is evaluated and tested at the beginning of each pass

through the loop. if it true it executes the body of the loop.When control reaches to closed braces, control return back to expr3 ass

If the loop continuation condition is initially false, the body part of the

loop is not performed

Any of the three parts can be omitted, but the semicolons must be kept

for(i=1;i


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for (i=1; i


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#include

void main(void)

{int n,i = 1, sum = 0;


scanf(%d,&n);

while ( i


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expr1,expr2 and expr3 in for can be replaced

by any valid expression.

ex:-

for (scanf(%d,&i);i


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If for loop have single statement we can omittthe curly braces.

for(i=1;i


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Int i=1;for(;i


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Executed from the inside out

Each loop is like a layer and has its own counter variable, its own loop

expression and its own loop body

In a nested loop, for each value of the outermost counter variable, the complete

inner loop will be executed once

General form

for (loop1_exprs) {

loop_body_1

for (loop2_exprs) {

loop_body_2}

loop_body_1b

}

Most compilersallow 15 nesting

levelsDONT

DO IT!!

Nested for loops


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Nested for loops

int i,j,sum;

for(i=1,i


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char ch= y

int i;

while(ch==y)

{

printf(\n enter the i value);scanf(%d,&i);

printf(%d =%d %d,i=i*i);

printf(\n do want to enter another i value);

scanf(%c,&ch);

}

break statement


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break statement is used to exit from the loop or

a block. When break statement is encountered control

automatically exit from the loop and passes to

the first statement after the loop. Use keyword break followed by semicolon.

break;

Write a program to find whether the given number is

prime or not


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#include

void main()

{int num,i;

printf(\n enter the number);

scanf(%d,&num);

i=2;

while(i


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the statements inside the loop which have not yet been executed.

When continue is encountered in the program the control automatically

goes to the beginning of the loop.

main()

{

int i,j;

for(i=1;i


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1. draw the block diagram of the computer. Explain about the components of thecomputer.

2. explain about the system development life cycle.

3. define algorithm and flowchart. Write an algorithm and flowchart for thefollowing problems.

a. largest of three numbers.

b. nature of quadratic equations.

4. explain about different data types in c language.

5. explain about the different operators in c language.6. explain about the repetitive control structures (while, do- while, for loops).

7. write a c program to find whether the given no is prime or not.

8. write a c program to display an institution gives grades to its students asfollows:

a. Grade A if he gets 80 or more marks

b. Grade B if he gets between 60 and 79(both inclusive)

c. Grade C if he gets between 50 and 59(both inclusive)

d. Grade D if he gets between 40 and 49(both inclusive)

e. Grade F otherwise.*/

Last date for submission- 29/10/2011

Towers of Honoi

Recursion a function which calls itself


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Recursion a function which calls itself.

To develop the algorithm for the recursive method use the

towers of Hanoi. Suppose three pegs, labeled A,B, and C are given, and suppose

on peg A there are placed a finite number of n disks indecreasing order.

The objective of the game is to move the disk from peg A topeg C using peg B as an auxiliary.

The rules of this problem are as follows

1. only one disk may be moved at a time. Specifically, only thetop disk on any peg may be moved to any other peg.

2. at no time can a larger disk be placed on a smaller disk.

A B C


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321

A B C

A->CA->B

C->B

A->C

B->AB->C

A->C

f(n)= 2n-1 moves for n disks

fibonacci sequence and golden ratio


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0,1,1,2,3,5,8,13.- fibonacci sequence

Golden ratio a/b=1.618

~algorithm for fibonacci sequence.1. read n

2. initialize a=0,b=1,i=2.

3. print a and b.

4. while( i


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g g

Algorithm

1. read n

2. while(n>0)

2.1 y=n%10

2.2 n=n/10

2.3 sum=sum+y

3. print sum

UNIT-II(c programming)

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