Why Does `sizeof('a')` Differ Between C and C ?

Character Size Differences in C and C

In both C and C , the sizeof operator provides information about the size of a data type or variable. By examining the output of a program using this operator, programmers can learn crucial details about the data they are working with. However, surprisingly, the sizeof operator yields different results when applied to a character value between C and C .

Consider the following C program:

#include <stdio.h>
int main(void) {
    printf("sizeof(char) = %zu\n", sizeof(char));
    printf("sizeof('a')  = %zu\n", sizeof('a'));
}

Upon execution, this program will print:

sizeof(char) = 1
sizeof('a')  = 4

Now, let's look at the same program written in C :

#include <iostream>
int main() {
    std::cout << "sizeof(char) = " << sizeof(char) << std::endl;
    std::cout << "sizeof('a')  = " << sizeof('a') << std::endl;
}

When run in C , it outputs:

sizeof(char) = 1
sizeof('a')  = 1

The key difference lies in how C and C represent character constants internally. In C, a character constant like 'a' is treated as an integer with the corresponding ASCII value. This is why sizeof('a') returns 4 in C, as the size of an integer is typically 4 bytes. On the other hand, in C , character constants are treated as the char data type, which has a size of 1 byte.

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