C strupr()

The strupr() is a non-standard function that is used to convert all lowercase letters in a string to their corresponding uppercase equivalents. It’s not a part of the standard C library, and its use is discouraged because it’s not portable across all C compilers.

If you need to convert a string to uppercase in a portable way, you can use the standard library functions and manually convert each character to uppercase using toupper() from the <ctype.h> header.

Here’s an example of how to manually convert a string to uppercase:

#include <stdio.h>
#include <ctype.h>

void stringToUpper(char *str) {
    for (int i = 0; str[i]; i++) {
        str[i] = toupper((unsigned char)str[i]);
    }
}

int main() {
    char str[] = "Hello, World!";
    stringToUpper(str);
    printf("Uppercase string: %s\n", str);
    return 0;
}

In this example, we define a function stringToUpper() that takes a string as an argument and converts it to uppercase character by character using toupper(). This approach is more portable and works with standard C functions and libraries.