The use of sizeof in C

The definition of sizeof is bellow

The sizeof keyword gives the amount of storage, in bytes, associated with a variable or a type (including aggregate types). This keyword returns a value of type size_t.

So, first sizeof is a keyword in C. And the sizeof can show the size of a data type and data structure in memory.

For example

#include <stdio.h>
int main(){
int a[]={1,3,4,5};
printf("%d",sizeof (a)/sizeof(a[0]));
}

The result of this program is 4

It has been shown that sizeof(a) is 16 which a is int array that contains 4 elements. And the sizeof (a[0]) is 4.