Example: String to Uppercase Manually in C

C
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// String to Uppercase Manually
#include <stdio.h>
#include <string.h> // For strlen

void toUpperCaseManual(char *str) {
    // Step 1: Iterate through the string until the null terminator is found.
    for (int i = 0; str[i] != '\0'; i++) {
        // Step 2: Check if the current character is a lowercase English letter.
        // ASCII values: 'a' is 97, 'z' is 122.
        if (str[i] >= 'a' && str[i] <= 'z') {
            // Step 3: Convert to uppercase by subtracting 32 from its ASCII value.
            // (e.g., 'a' (97) - 32 = 'A' (65))
            str[i] = str[i] - 32;
        }
    }
}

int main() {
    char myString[] = "Hello, World! 123";

    printf("Original string: %s\n", myString);

    // Step 4: Call the toUpperCaseManual function.
    toUpperCaseManual(myString);

    printf("Uppercase string: %s\n", myString);

    return 0;
}