The C Sizeof operator is one of operators which is mostly useful to find the array size, structure size, and do some calculations as per the results.
The C sizeof operator returns the size (number of bytes) of a declared variable or data type. Let us see one C programming example for better understanding
C Sizeof Operator Example
In this Operator example program, We are going to check the size of an integer, float, character, double and character array using sizeof operator.
#include <stdio.h> int main() { int a; int b[20]; printf(" Size of int data type:%d \n ", sizeof(int) ); printf(" Size of char data type:%d \n ", sizeof(char) ); printf(" Size of float data type:%d \n ", sizeof(float) ); printf(" Size of double data type:%d \n ", sizeof(double) ); printf(" Size of int data type:%d \n ", sizeof(a) ); printf(" Size of an int array:%d \n ", sizeof(b) ); return 0; }

The result of sizeof(b): Although we declared the size of the b as 20, it displays output as 80. Because b array will store 20 integer members. And every integer member needs 4 bytes of space ( means 20 * 4 Bytes for every integer member.)