#include <stdio.h>
int main()
{
int a;
long b;
long long c;
double e;
long double f;
printf("Size of int = %ld bytes \n", sizeof(a));
printf("Size of long = %ld bytes\n", sizeof(b));
printf("Size of long long = %ld bytes\n", sizeof(c));
printf("Size of double = %ld bytes\n", sizeof(e));
printf("Size of long double = %ld bytes\n", sizeof(f));
return 0;
}

Output

Size of int = 4 bytes 
Size of long = 8 bytes
Size of long long = 8 bytes
Size of double = 8 bytes
Size of long double = 16 bytes

In this program, the sizeof the operator is used to find the size of int, long, long long, double and long double.

The long keyword cannot be used with float and char type variables.

program in C that demonstrates the use of the “long” keyword:

#include <stdio.h>

int main() {
    int num1 = 10;
    long num2 = 1000000000;
    
    printf("Size of int: %d bytes\n", sizeof(num1));
    printf("Size of long: %d bytes\n", sizeof(num2));
    
    printf("Value of num1: %d\n", num1);
    printf("Value of num2: %ld\n", num2);
    
    return 0;
}

In this program, we have declared two variables: “num1” and “num2”. “num1” is an integer variable and “num2” is a long integer variable.

We then use the “sizeof” operator to print out the size of the integer and long integer data types. The output of this program would be:

Size of int: 4 bytes
Size of long: 8 bytes
Value of num1: 10
Value of num2: 1000000000

As we can see, the “long” keyword is used to declare a variable that can store larger integer values than the “int” data type. In this case, the “long” integer can store a value of up to 2^63-1, whereas the “int” data type can only store up to 2^31-1.