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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.

Declaration of Variable
#include <stdio.h>
void main(){
int a1, a2;
int a_1;
void main ( ){ 
char b_1;
double db;
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
void main ( ){
float b1 ;
b1 = 2.302;
double a;
a = 7.202;
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.


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