#include <stdio.h>
int main() {
char a = 'A';
int b = 90000;
float c = 6.5;
printf("%d ",sizeof(6.5));
printf("%d ",sizeof(90000));
printf("%d ",sizeof('A'));
printf("%d ",sizeof(c));
printf("%d ",sizeof(b));
printf("%d",sizeof(a));
return 0;
}
The output is:
8 4 4 4 4 1
Why is the output different for the same values?
Character constants in C (opposite to C++) have the type int. So this call
printf("%d",sizeof('A'));
outputs 4. That is sizeof( 'A' ) is equal to sizeof( int ).
From the C Standard (6.4.4.4 Character constants)
10 An integer character constant has type int....
On the other hand (6.5.3.4 The sizeof and alignof operators)
4 When sizeof is applied to an operand that has type char, unsigned char, or signed char, (or a qualified version thereof) the result is 1.
So the operand of the sizeof operator in this expression sizeof( 'A' ) has the type int while in this expression sizeof( a ) where a is declared like
char a = 'A';
the operand has the type char.
Pay attention to that calls like this
printf("%d",sizeof(6.5));
use incorrect conversion format specifier. You have to write
printf("%zu",sizeof(6.5));
Also in the above call there is used a constant of the type double while in this call
printf("%zu",sizeof(c));
the variable c has the type float.
You could get the same result for these calls if the first call used a constant of the type float like
printf("%zu",sizeof(6.5f));