ANSI C American National Standards Institute

Importance of C

1. Robust language: Rich built in functions and operators can help in developing complex programmes

2. Suitable for developing system software and business package: C compiler combines assembly language and high level language capabilities.

3. Fast and Efficient

4. Highly portable: Computer to computer portability, even to new operating system.

5. Structured programming: function modules or blocks.

6. Easy for debugging, testing and maintenance.

7. Ability to extent itself: Add our own functions to the C library.

Character set in C

Letters A … Z ( Upper case) a …. z (Lower case) Digits 0 … 9 White spaces Blank space Horizontal tab Carriage return New line Form feed

, Comma

. Period

; Semicolon

: Colon

? Question mark

‘ Apostrophe

“ Quotation mark

! Exclamation mark

| Vertical bar

/ Slash

\ Back slash

~ Tilde

_ Underscore

$ Dollar sign

% Percentage sign (Modulo)

& Ampersand

^ Caret

* Asterisk

- Minus sign

+ Plus sign

< Opening angle bracket (Less than sign)

> Closing angle bracket (greater than sign)

( Left parenthesis

) Right parenthesis

[ Left bracket

] Right bracket

{ Left brace

} Right brace

# Number sign (Hash)

Special characters

Basic Structure of C programs

Documentation section

Link Section

Definition section

Global declaration section

main () Function section

{

Declaration part

}

Sub program section

Function 1

Function 2

.

.

Function n

Basic C program

main ()

{

/*………printing begins……..*/

printf(“This is a model programme”);

/*………printing ends……..*/

}

Function name

Start of the programme

Programme statements

End of the programme

Comments

#include

main () { printf(“This is a model programme”); }

Constants

Constants

Numeric constants

Real constants Integer

constants

Character constant

Single character constant

String constants

Fixed values that do not change its value during the execution of a programme.

1233 -342 0 1322034032 +4323

0.0394 -0.234 +234.2343 456.0 1.6e-19

Mantissa e exponent

a 5 ; “

“hello” “1987” “Welldone”

Variables

Variable is a data name that may be used to store data value. The value in the variable can

change in different times during the execution of the programme.

Can take any name (Identifier) : Averaga, height, Total, class_strength, Employee_1 etc..

Rules for selecting identifier:

1. Letters digits and (_) Underscore are allowed.

2. They must begin with a letter. Some may permit use of _ as first character.

3. ANSI standard recognises length of the name as 31 characters. But still many compilers

takes only first 8 characters.

4. Uppercase and lower case are different.

5. It should not be a keyword

6. White space not allowed

Data types 1. Primary Data type (Fundamental data type)

Integer: int, short int, long int, unsigned int, unsigned short int, unsigned long int

Character: char, signed char,unsigned char

Floating : float, double, long double

Void : void

2. Derived Data type: Array, function, pointer etc. 3. User defined data type: typedef structure union

Type Storage size Value range

char 1 byte -128 to 127 or 0 to 255

unsigned char 1 byte 0 to 255

signed char 1 byte -128 to 127

int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647

unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295

short 2 bytes -32,768 to 32,767

unsigned short 2 bytes 0 to 65,535

long 4 bytes -2,147,483,648 to 2,147,483,647

unsigned long 4 bytes 0 to 4,294,967,295

Float 2 or 4 byte

16 bit or 32 bit machine

Double 8 byte 14 digit precision

Declaration of variables

Before using a variable, we must declare them to the compiler.

1. It tells the compiler what the variable name is

2. It specifies what type of data the variable hold and suitable memory is allotted.

Primary type declaration

data-type var1, var2, var3… varn; // Syntax

Eg: int count;

int number, total;

double ratio;

User defined data type declaration

typedef type identifier; // Syntax

Eg: typedef int units;

typedef char name;

units batch1, batch2;

name std1, std2;

Assigning values to variables

Variable_name = constant; //syntax

Eg: initial_value = 1;

final_value = 100;

interest = 9.34;

yes = ‘x’;

Initialisation (Assigning value before using the variable)

data-type variable_name = constant; // Syntax

Eg: int initial_value = 1;

int final_value = 100;

float interest = 9.34;

char yes = ‘x’;

‘=‘ assignment operator

Defining symbolic constants

#define symbolic_name valueofconstant //syntax

Eg: #define Strength 100

#define PASS_Mark 50

#define pi 3.14159

Rules

1. Symbolic_name should be an identifier.

2. No blank space between # and define

3. Blank space is required after #define and after symbolic_name

4. No end semicolon.

5. No equal sign on assigning values

6. #define may appear anywhere in the program but before the constant is used in the

program.

Declaring a variable as constant

const data-type identifier = value; //syntax

Eg: const int Strength = 100;

const int PASS_Mark = 50;

const float pi = 3.14159;

Declaring a variable as volatile :- means the value may change during the programme

volatile data-type identifier ; //syntax

volatile data-type identifier = value; //syntax

Eg: volatile int date;

volatile const int number = 100; // declared as both volatile

and constant

Input/Output functions

Input functions

stdio.h

Function Syntax Usage

getchar( ); Variable_name = getchar( ); char name;

name= getchar( );

scanf( );

scanf(“control string”, arg1, arg2, ,.. argn);

scanf(“control string”, &variable1, &variable2,..);

scanf(“%d”, &number);

scanf(“%d %d”, &nmb1, &nmb2);

scanf(“%2d %4d”, &nmb1, &nmb2); • Gets 2 digit integer for first number and

4 digit integer for second. • If more data added, it will be considered

for next input function.

Format string

Formatted input

scanf (“%d %c %f %s”, &count, &code, &ratio, name); Reading mixed data type

15 p 1.575 coffee

Input/Output functions

Output functions

stdio.h

Function Syntax Usage

putchar( ); putchar (variable_name);

char answer;

answer = ‘Y’;

putchar (answer);

printf( ); printf(“control string”, variable1, variable2,..); printf(“Programme in C”);

printf(“sum = %d”, 1234);

printf(“%d”, 9876);

printf(“%6d”, 9876);

printf(“\n”);

printf(“a= %d\n b= %d”, nmb1, nmb2);

9876

9876

% w.p type-specifier Minimum filed width of specifier

Rules of scanf( );

1. Each variable to be read must have a field specification.

2. All function arguments except the control string must be pointers to variables.

3. Format specificaions contained in the control string should match the arguments in

order.

4. scanf() ignores bondaries and simply looks for the next appropriate character.

5. Any unread data items in a line will be considered as part fo the data input line to the

next scanf() call.

6. Never end the format string with whitespace. IT IS AN ERROR.

7. scanf reads until:

• Whitespace character is found in a numeric specification or

• The maximum number of characters have been read or

• An error is detected or

• The end of file is reached.

8. scanf() returns the number of data received from the keyboard. In case of error the

returned integer will have lesser value than specified.

Code Meaning for scanf() Meaning for printf()

%c Read a single character Print a single character

%d Read a decimal integer Print a decimal integer

%e Read a floating point value Print a floating point value in exponential form

%f Read a floating point value Print a floating point value without exponential form

%g Read a floating point value Print a floating point value either e-type or f-type depending on value

%h Read a short integer

%i Read a decimal, hexadecimal or octal integer

Print a signed decimal integer

%o Read an octal integer Print an octal integer without leading zero

%s Read a string Print a string

%u Read an unsigned decimal integer Print an unsigned decimal integer

%x Read a hexadecimal integer Print hexadecimal integer, without leading 0x

%[..] Read a string of word(s)

- Left justified + precede the signed numeric with + or – # precede 0 or 0x and present floating point number with decimal point Ever if it is whole number

Operators

1. Arithmetic Operators +, -, *, /, % :- integer arithmetic and real arithmetic

2. Relational Operators =, ==, !=

3. Logical Operators &&, ||, !

4. Assignment operators =, +=, -+, *=, /=, %= a+=1 means a=a+1

5. Increment and decrement operators ++, --

6. Conditional operators ?: exp1?exp2:exp3 x = (a > b) ? a : b; ternary operator

7. Bitwise operators &, |, ^,

8. Special operators comma operator, sizeof operator,

If statement

if(test expression) { Statement block; } Statement -X

Statement block

Statement -X

Next statement

Entry

True

False

Test expression ?

If … else statement

if(test expression) { True block statements; } else { False block statements; } Statement – X Next statement

False block statement(s)

Statement -X

Next statement

Entry

True False Test expression ?

True block statement(s)

Nesting of If … else statement if(test condition 1) { if (test condition 2) { statement 1; } else { statement 2; } } else { if (test condition 3) { statement 3; } else { statement 4; } }

The else if Ladder

if(test condition 1)

Statement 1;

else if (test condition 2)

statement 2;

else if (test condition 3)

statement 3;

else if( test condition n)

statement n;

else

default statement;

statement.;

The switch statement switch ( expression )

{

case value-1:

block 1

break;

case value-2:

block 2

break;

……….

………..

default:

default block

break;

}

Next statement

The goto statement

Forward Jump

goto label;

………. ……….. ………

………. ……….. ………

………. ……….. ………

………. ……….. ………

label:

statement;

Backward jump

label:

statement;

………. ……….. ………

………. ……….. ………

………. ……….. ………

………. ……….. ………

goto label;

The while loop

while (test condition) { body of the loop; }

main ( )

{

int count, n=1;

printf(“Enter an integer value :”);

scanf(“%d”, &count);

printf(“Integers upto %d are”, n);

while(n

The do loop

do { body of the loop; } while (test condition);

main ( )

{

int count, n=1;

printf(“Enter an integer value :”);

scanf(“%d”, &count);

printf(“Integers upto %d are”, n);

do

{

printf(“\n %d”, n);

n = n+1;

}

while(n

The for loop

for( initialization condition; test condition; increment ) { body of the loop; } main ( )

{

int count, n;

printf(“Enter an integer value :”);

scanf(“%d”, &count);

printf(“Integers upto %d are”, n);

for (n=1; n

The jump statements

goto

Go to a label

break;

Breaks from a loop

Continue

Skip the remaining step and continue from the condition statement of a loop.

exit()

Exits from a program .

exit(0);

Array

List of items with same variable name. One dimensional array

[0]

[1]

[2]

[3]

[4]

X x[0], x[1], x[2], x[3], x[4] :- number of elements n. ie 0 to n-1 Allots separate memory location for each variable. 35

0

546

-1

6453

Declaration type array_name[size]; //syntax int height[10]; int x[5]; Initialisation 1. Compile time:

type array_name[size] = {list of values};

int x[5] = {35, 0, 546, -1, 6453}; 2. Run time: type array_name[size]; ………….. for(n=0;n

Two dimensional array

[0] [1] [2] [3]

[0] X[0][0] X[0][1] X[0][2] X[0][3]

[1] X[1][0] X[1][1] X[1][2] X[1][3]

[2] X[1][0] X[2][1] X[2][2] X[2][3]

[3] X[3][0] X[3][1] X[3][2] X[3][3]

[4] X[4][0] X[4][1] X[4][2] X[4][3]

columns

Ro

ws

type array_name[sizeofrow][sizeofcolumn]; int x[5][4];

for(i=0 ; i

main( ) { ………………….. ………………… function1( ); ………………….. ……………………… function2( ); ……………………… ………………………… function1( ); }

Functions in C

• Building block of a programme

• Sub programme of program.

• Modular programme

• Sub set of main program.

function1( ) {…………………….. ………………… }

function2( ) { ……………………. function3(); …………………… }

function3( ) {…………………….. ………………… }

Requirements of a function

1. Function definition

2. Function call

3. Function declaration

return_type function _name ( parameter,list ) { local variable declaration; //body of the function execution statements; ……………………………….. return (expression ); //return statement }

function_name ( arguments );

return_type function _name ( list, of, parameter, data-types );

Functions in C

float read_data ( void ); float mul (float , float); void write_data(float); main ( ) { float x, y,z; x = read_data ( ); y = read_data ( ); z = mul (x, y); write_data (z); }

float read_data (void) { float a; printf(“Enter a data \n”) scanf(“%f “, &a); return (a); } float mul (float p, float q) { float prod; prod = p * q; return (prod); } void write_data (float result) { printf (“The product of entered data is : %f”, result); :}

Standard library functions of ANSI C?

Assignment

Recursion function

factorial ( int n) { int fact; if (n ==1);; return(1); else fact = n*factorial(n-1); return (fact); }

Recursion is a process in which a function calls itself in its body.

Nesting of function

Nesting is a process in which a second function is called inside the body of a function.

Structure

Conveniently group different types of data in one bundle.

1. Structure definition

2. Structure variable declaration

struct structure_name, obj1, obj2, obj3;

3. Accessing structure members

object . variable

struct structure_name { data-type variable1; data-type variable2; . . }; // close with ‘;’ is very important

Struct book_details { char title[20]; char author[15]; int pages; float price; };

struct book_details, book1, book2;

book1.price = 395.50; book2.price = 982.00;

Pointer

Pointer is a datatype which contains the memory address. Pointers can access and manipulate data stored in the memory.

1. Accessing memory

& -operator

Eg: &a &p[5] etc.

2. Declaration of pointer

data_type * pt_name;

Eg: int *p; float *x;

3. Initialization of pointer variable

int quantity;

int *p;

p = &quantity;

4. Accessing a variable through its pointer

n = *p;

179

quantity

5000

Variable

Value

Address

5000

p

8000

Variable

Value

Address

File operations

1. Defining and opening a file FILE *fp; fp = fopen ( “filename”, “mode” );

2. Closing a file

fclose (file_pointer);

FILE *p1, *p2; p1 = fopen(“INPUTT”, “w”); p2 = fopen(“OUTPUT”, “r”); . . fclose (p1); fclose (p2);

fopen (), fclose(), getc(), putc(), fprintf(), fscanf(), putw(), getw(), fseek(), ftell(), rewind()

filename: primaryname ‘Period’ Extension

Prog.c

Text.out Inp.data

File operations

INPUT/OUTPUT Operations

getc(), putc() : handles one character at a time, similar to getchar and putchar. putc(variable, file_pointer); putc(a, fp1); variable = getc (file_pointer); b = getc (fp2);

fprintf(), fscanf() fprintf (file_pointer, “control string”, list); fprintf (fp1, “%d %s %f”, slno, name, price); fscanf (file_pointer, “control string”, list); fscanf (fp1, “%d %s %f”, slno, name, price);

getw and putw are integer oriented functionsused to read and write integer values.