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C Programming variables, Constants & Data Types

Variables - Variables are simply names used to refer to some location in memory a location that holds a value with which we are working. It may help to think of variables as a placeholder for a value.

Constants - Constants refer to fixed values that the program may not alter(change) during its execution. These fixed values are also called literals. Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant.

Data Types - It defines the type of data any variable is going to store. Data types are Predefined & User Defined. Detailed list of Data Type -

Predefined Data Types

Data TypeStorage SizeRange
char 1 byte-128 to 127 or 0 to 255
unsigned char 1 byte 0 to 255
signed char 1 byte -128 to 127
int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295
short 2 bytes -32,768 to 32,767
unsigned short 2 bytes 0 to 65,535
long 8 bytes -9223372036854775808 to 9223372036854775807
unsigned long 8 bytes 0 to 18446744073709551615
float 4 byte 1.2E-38 to 3.4E+38 [Precision - 6 decimal places]
double 8 byte 2.3E-308 to 1.7E+308 [Precision - 15 decimal places]
long double 10 byte 3.4E-4932 to 1.1E+4932 [Precision - 19 decimal places]

User Defined Data Types

Use defined data types are Structure, Union, and Enumeration. Size of each user defined data types depends on the size of their memebers. We will discuss size of each user defined data type in details here -

Size of Structure

To calculate size of structure let create one basic example here


#include<stdio.h>

struct student{
int age;
int std;
};

void main()
{

printf("\n Size of student is : %d bytes ", sizeof(struct student));

}

Size of union

To calculate size of union let create one basic example here


#include<stdio.h>

union student{
int age;
int std;
};

void main()
{

printf("\n Size of student is : %d bytes ", sizeof(union student));

}

Size of enum

To calculate size of enum let create one basic example here


#include<stdio.h>

enum BMWcolor{
RED,BLUE, BLACK
};

void main()
{

printf("\n Size of student is : %d bytes ", sizeof(enum BMWcolor));

}

NOTE - sizeof() is open operator in C programming, which can be used to calculate size of predefined & user defined data types.