In this tutorial we will learn about variable and data types in c language. First we will learn why we need variables in c, and after that about different data types in c language. Now look at the below code,

#include<stdio.h>
int main()
{
	int n,m,s;	
	n=10;
	m=30;
	s=n+m;
	printf("\nSum : %d",s);
	return 0;
}

In the above C code, you need to focus on first line of main() function,that is “int n,m,s”.

• int – This is called data type, Integer data type.
• n,m,s – These are variables of integer type.

What is Variable in C Language

• Variable is a memory location.
• It can store some values.
• Value of a variable can changed, during programming.

Naming Rules for Variable

• Name of a variable can be combination of letters, numbers and underscore.
• First character of variable name should not be a number, it must start with character or underscore.
• A variable name can have both uppercase and lowercase or combination of both case.
• Variable name should not be a reserve keyword(predefined word in C, ex. void, break etc.).
• Name of variable should be meaningful.

Data Types in C Language

Here we will learn about different data types in C language and format of data type in C programming. Whenever you declare a variable in c, you need to specify a type of data to be store in variable as data type. Each data type in C Language has specific format for input or print a variable. We will discuss it in detail about why and how to use this with example.

List of Data Types

• char – To store single character value.
• int – Used to store whole numbers.
• float – float is used to store decimal number with single precision.
• double – To store decimal number with double precision.

Signed and Unsigned Modifier in C

In C signed and unsigned modifier can be used with char and int data types. It is related to positive and negative values. By default char and int are signed type.

• signed – default modifier, can store both negative and positive values.
• unsigned – It can store zero or positive values.

Data Type with Format Specifier in C

Data Type	Size in Bytes	Range	Format Specifier
signed char	1	-128 to 127	%c
unsigned char	1	0 to 255	%c
short int	2	-32,768 to 32,767	%hd
unsigned short int	2	0 to 65,535	%hu
unsigned int	4	0 to 4,294,967,295	%u
int	4	-2,147,483,648 to 2,147,483,647	%d
long int	4	-2,147,483,648 to 2,147,483,647	%ld
unsigned long int	4	0 to 4,294,967,295	%lu
long long int	8	-(2^63) to (2^63)-1	%lld
unsigned long long int	8	0 to 18,446,744,073,709,551,615	%llu
float	4	1.2E-38 to 3.4E+38 (6 decimal places)	%f
double	8	2.3E-308 to 1.7E+308 (15 decimal places)	%lf
long double	12	3.4E-4932 to 1.1E+4932 (19 decimal places)	%Lf

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