How to find the size of data type using sizeof() operator in C

Sizeof(type) is a unary operator used to calculate the size(in bytes) of any datatype in C.

Syntax:

sizeof(type)
Note: type must be replaced by a valid C data type or variable.

Example:


#include <stdio.h>

int main()
{
int i;
printf("Size of int = %dn", sizeof(int));
printf("Size of i = %dn", sizeof(i));
return 0;
}

Output:

Size of int = 4
Size of i = 4

Calculating the size of struct and array:


#include <stdio.h>

struct Student {
int roll; //Will take 4 bytes
char name[30] //Will take total 1*30 bytes
}stu;

int main()
{
printf("Size of Student = %dn", sizeof(struct Student));
printf("Size of Student = %dn", sizeof(stu));
printf("Size of Student.roll = %dn",sizeof(stu.roll));
printf("Size of Student.name = %dn",sizeof(stu.name));

return 0;
}

Output:

Size of Student = 36
Size of Student = 36
Size of Student.roll = 4
Size of Student.name = 30

Note: size of struct should be 34 bytes buts its takes 36 bytes because the compiler adds extra 1 byte for alignment and performance at the end of each structure members.

Program to calculate size of different data types:


#include <stdio.h>

int main()
{
printf("Size of char = %dn", sizeof(char));
printf("Size of short = %dn", sizeof(short));
printf("Size of int = %dn", sizeof(int));
printf("Size of long = %dn", sizeof(long));
printf("Size of long long = %dn", sizeof(long long));
printf("Size of float = %dn", sizeof(float));
printf("Size of double = %dn", sizeof(double));
printf("Size of long double = %dn", sizeof(long double));

return 0;
}

Output:

Size of char = 1
Size of short = 2
Size of int = 4
Size of long = 4
Size of long long = 8
Size of float = 4
Size of double = 8
Size of long double = 12

Note: All size are in bytes and may vary on different platform.

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