C Programming: Replace every lowercase letter with the same uppercase

Last update on March 20 2025 12:42:28 (UTC/GMT +8 hours)

40. Replace Lowercase with Uppercase

Write a C program to replace each lowercase letter with the same uppercase letter of a given string. Return the newly created string.

Sample Data:

("Python") -> "PYTHON"
("abcdcsd") -> "ABCDCSD"

Sample Solution-1:

C Code:

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

// Function to replace lowercase letters with their uppercase counterparts
char * test(char * text) {
    // Check if the string is empty
    if (!text[0])
        return "No string found.";

    char *tt = text;

    // Loop through the string
    while(*tt != '\0') {
        // If the current character is a lowercase letter, convert it to uppercase
        if (*tt >= 'a' && *tt  <= 'z') {
            *tt = *tt + 'A' - 'a'; // Conversion to uppercase
        }
        tt++;
    }
    return text;
}

int main() {
    // Example strings for testing
    //char text[50] = "";
    char text[50] = "Python";
    //char text[50] = "abcdcsd";

    printf("Original string: %s", text);
    printf("\nReplace each lowercase letter with the same uppercase in the said string:\n%s ", test(text));
    return 0;
} 

Output:

Original string: Python
Replace each lowercase letter with the same uppercase in the said string:
PYTHON 

Flowchart:

Sample Solution-2:

C Code:

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

// Function to replace lowercase letters with their uppercase counterparts
char * test(char * text) {
    // Check if the string is empty
    if (!text[0])
        return "No string found.";

    int i, str_len = strlen(text);
    // Allocate memory for the resulting string with the same length as the input
    char * result_str = (char *) malloc(sizeof(char) * str_len);

    // Loop through each character in the string
    for (i = 0; i < str_len; i++) {
        // If the character is a lowercase letter, convert it to uppercase
        if (*(text + i) >= 'a' && *(text + i) <= 'z') {
            *(result_str + i) = *(text + i) - 32; // Conversion to uppercase
        } else {
            *(result_str + i) = *(text + i); // Keep the character unchanged if it's not a lowercase letter
        }
    }

    *(result_str + str_len) = '\0'; // Add the null terminator to mark the end of the string
    return result_str;
}

int main() {
    // Example strings for testing
    //char text[50] = "";
    //char text[50] = "Python";
    char text[50] = "abcdcsd";

    printf("Original string: %s", text);
    printf("\nReplace each lowercase letter with the same uppercase in the said string:\n%s ", test(text));
    return 0;
}

Output:

Original string: abcdcsd
Replace each lowercase letter with the same uppercase in the said string:
ABCDCSD 

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to convert all lowercase letters in a string to uppercase without using library functions.
• Write a C program to iterate over a string and transform every lowercase letter to its uppercase equivalent using ASCII arithmetic.
• Write a C program to convert a string to uppercase and display both the original and modified strings side by side.
• Write a C program to change lowercase letters to uppercase while simultaneously reversing the string.

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