Data Structure and c

K.S.PrabhuLecturer

All Deaf Educational Technology

C Tokens

C Tokens

Keywords

• It has 32 keywords. 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

#include<stdio.h>#include<conio.h>void main(){char yn;clrscr();do{

puts("enter y/n(yes/no)");yn=getchar();fflush(stdin);if(yn!='y'&&yn!='n')puts("invalid input");}while(yn!='y'&&yn!='n'); getch();

Constants A constant is an entity that doesn't change

during the execution of a program.

Followings are the different types of constants.

1)Real constant2)Integer Constant 3)Character Constant 4)String Constant

1. Real Constant :

• It must have at least one digit.• It must have a decimal point which may be

positive or negative.• Use of blank space and comma is not allowed

between real constants.• Example:•

+194.143, -416.41

Real Constant

• It must have at least one digit.

• It must have a decimal point which may be positive or

negative.

• Use of blank space and comma is not allowed between

real constants.

• Example:

+194.143, -416.41

Integer Constant

• It must have at least one digit.

• It should not contain a decimal place.

• It can be positive or negative.

• Use of blank space and comma is not allowed between

real constants.

• Example:

•

1990, 194, -394

Character Constant

• It is a single alphabet or a digit or a special

symbol enclosed in a single quote.

• Maximum length of a character constant is 1.

• Example:

'T', '9', '$'

String Constant

• It is collection of characters enclosed in double quotes.

• It may contain letters, digits, special characters and

blank space.

• Example:

“I love Deaf“

“ All Deaf Educational Technology”

Identifier

• An identifier is used for any variable, function, data definition, etc.

• In the C programming language, an identifier is a combination of alphanumeric characters.

• An underline and the remaining being any letter of the alphabet, any numeric digit, or the underline.

String

• Strings in C are represented by arrays of

characters.

• The end of the string is marked with a special

character, the null character, which is simply the

character with the value 0.

• The null character has no relation except in name

to the null pointer.

char string[15] = "Hello world!";

Sample code Program

#include<stdio.h>#include<conio.h>void main(){char in_str[21];clrscr();

puts("Enter a string to a maximum of 20 characters");getch();} outputEnter a string to a maximum of 20 characters

Youth •

Variables

• It is date name used date value called by valuables.

• It is a data name which is used to store data and may change during program execution.

• It is opposite to constant.

• Variable name is a name given to memory cells location of a computer where data is stored.

Syntax:

{data types}{Variables name} =[value]

Sample code Program

Example:Int count index;Float area price;Chal class types;

Example of main program:-

Main{ Int a,b,c,=10; Char x; Float num;

Types of variables

Local variables

•These variables only exist inside the specific function that creates them.

•They are unknown to other functions and to the main program.

•As such, they are normally implemented using a stack.

• Example:• {• Int a, b, c, =10; local variable• Char x;• Float num;• }

Global variables

• These variables can be accessed by any function comprising the program.

• They are implemented by associating memory locations with variable names.

• Example:• {Int a, b, c, =[10,20,30] ; Global variable• Chal x;• Float• } (or)• {Int a = [10]• Int b = [20]• Int c = [30]• Chal [15]• Float• }

Example of Global Variable

Example:{

Int a, b, c, =[10,20,30] ; Char x;Float num;}

{ Int a = [10]; Int b = [20]; Int c = [30]; Char[15]; Float num;}

TYPEDEF STATEMENT

• typedef is a keyword in the C and C++ programming languages.

• The purpose of typedef is to assign alternative

names to existing types.

• types declared with typedef end with ( '_t' )• (e.g., size_t, time_t)Syntax;-• Typedef exp1, exp2,….., exp n

• All data types in between typedef and identifier can now be referred to by the identifier alone The statement.

typedef struct tnode *Treeptr; typedef struct tnode { int count; struct tnode *left; struct tnode *right; } Treenode;

Example of Typedeaf

Enumerated DataTypes

•The data type enum allows used identifier as value

•Syntax:• Enum identifier {Element} Element 1, Element 2…..to Element n;

Example of main program

• Enum days {sun, mon, tue, wed, thu, fir, sat}

• Enum color{red, blue, orange, pink, green,}

• Enum holiday{Sunday, Saturday}

• Enum rainbow {red, blue, orange, yellow,

green,}