1. String Literals Include a Null Terminator

When you write "Hello", the compiler automatically appends a null character (\0) at the end to indicate the end of the string.

So, "Hello" in memory is actually:

['H', 'e', 'l', 'l', 'o', '\0']

Thus, sizeof("Hello") counts all 6 bytes, including the \0

2. Difference Between sizeof and strlen

• sizeof("Hello") returns 6 at compile-time because it includes the null terminator

• strlen("Hello") returns 5 at runtime because it counts only characters until \0

Example:

#include <stdio.h>
#include <string.h>

int main() {
    printf("sizeof: %lu\n", sizeof("Hello"));  // Output: 6
    printf("strlen: %lu\n", strlen("Hello"));  // Output: 5
    return 0;
}

How to Avoid This Confusion?

• Use strlen() when you need the actual string length

• Use sizeof() only if you need memory size allocation, such as for a character array