Data Structure and c K.S.Prabhu Lecturer All Deaf Educational Technology

C Tokens

Float while Key word Real Unreal constant

Identifier MainAmount String NameAge

Brace Curly Special Symbol Plus Minus Operators

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 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 constant 2)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: ,

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: ,

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 void main() { char in_str[21]; clrscr(); puts("Enter a string to a maximum of 20 characters"); getch(); } output Enter 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 variable Global variable

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 1055

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,}