Constants and Variables in C

 

Constants in C: Constants are the terms that can't be changed during the execution of a program.

Examples: Integer Constants: 0, 1, 2, 3, 4, 5, 6, 7 . . . . . . .

Floating Constants: 0.0, 0.1, 0.2, 0.3, -0.4, 0.5, 5.1546, 2.5465, -1.02545 . . . . . . . 

Character  Constants:  Character  constants  are  the  constant  which  use  single  quotation  around 

characters. For example: 'a', 'l', 'm', 'F' etc.

Variables in C: Variables are memory location in computer's memory to store data. To indicate the memory location, each variable should be given a unique name called identifier. Variable names are just  the  symbolic  representation  of  a  memory  location.  Examples  of  variable  name:  ABC,  var_no, var_123, Var123, Count etc.

Basic Data Types in C: 

Char: a single byte that can hold a character (‘a’, ’b’, ’c’, ’d’, ’e’ . . . . . . . ) 

Int: An Integer can hold 2 or 4 byte integers (0, 1, 2, 3, 4, 5, 6, 7 . . . . . . .)

Float: A float can hold 4 byte floating points (0.0, 0.1,0.2, 0.3, -0.4,0.5,5.1546, 2.5465, -1.02545 . . .)

Double: Double is same as float just the difference is it can hold up to 8 byte (0.0, 0.1, 0.2, 0.3, -0.4, 

0.5, 5.1546, 2.5465, -1.02545 . . . . . . .)

Rules for writing variable name in C:

The first letter of a variable should be a letter, Variable name can be made up of both uppercase and lowercase letters, digits and underscore (_) only.
Examples:

Declaration of Variable
#include <stdio.h> void main(){ int a1, a2; int a_1; }	#include<stdio.h> void main ( ){  char b_1; double db; }	#include<stdio.h> void main(){ float a_1, b2, b3, b4; char jvh; }
a1, a2 and a_1 are declared as integer now they can store integers.	b_1 and db are declared as char and do uble respectively now b_1 can store characters(fonts) and db can store fractioned numbers.	Here a_1, b2, b3, b4 can store floating points and jvh can store charac

Initialization of Variable
#include<stdio.h> void main ( ){ float b1 ; b1 = 2.302; double a; a = 7.202; }	#include<stdio.h> void main ( ){  char b_1 ; b_1 = ‘r’; int a; a = 7; }	#include <stdio.h> void main(){ int a1 = 5; int b1; b1 = 5;  }
B1 and a are declared and initialized.	Here b_1 is stores / initialize r And a store’s 7 ..	a1 is initialized during declaration and b1 firstly initialize then declare on second line.