Copy string converting lower to upper using pointer

Logic. The function copyUpper(char *src, char *dest) walks along the source string with the pointer src. For each character *src: if it lies between 'a' and 'z', 32 is subtracted (the ASCII code of a small letter is 32 more than that of the capital letter) and stored through dest; otherwise it is copied unchanged. Both pointers are incremented after every character, and '\0' is added at the end of dest. No array subscripts are used.

#include <stdio.h>

/* copy src to dest, converting lower case letters to upper case */
void copyUpper(char *src, char *dest)
{
    while (*src != '\0') {
        if (*src >= 'a' && *src <= 'z')
            *dest = *src - 32;        /* 'a'(97) - 32 = 'A'(65) */
        else
            *dest = *src;
        src++;
        dest++;
    }
    *dest = '\0';
}

int main(void)
{
    char s1[100], s2[100];
    printf("Enter a string: ");
    fgets(s1, sizeof s1, stdin);
    for (char *p = s1; *p; p++)
        if (*p == '\n') *p = '\0';
    copyUpper(s1, s2);
    printf("Original: %s\nCopied  : %s\n", s1, s2);
    return 0;
}

Sample run

Input: Hello World 2024 from Nepal

Enter a string: Original: Hello World 2024 from Nepal
Copied  : HELLO WORLD 2024 FROM NEPAL

Digits and spaces are unchanged; only the lower case letters are converted.