C Function to Convert a String to Uppercase: Design Guide

Uppercase String Conversion in C: Step-by-Step Function Design

"Design a function to convert given string into upper character using own function" means to create a function in the C programming language that can take a string as input and convert all of its characters to uppercase using your own implementation, without relying on any built-in functions or libraries.

To design a function to convert a given string to upper case in C, we can use the following approach:

Define a function with the following signature:

char *touppercase(char *string);

The function will take a pointer to the string to be converted as input and return a pointer to the converted string as output.

2. Inside the function, iterate over the string character by character.
3. For each character, check if it is a lowercase letter. If it is, convert it to the corresponding uppercase letter by subtracting 32 from its ASCII value.
4. Return the pointer to the converted string.

Complete implementation of the touppercase() function:

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

char *touppercase(char *string) {
  char *ptr = string;
  while (*ptr != '\0') {
    if (*ptr >= 'a' && *ptr <= 'z') {
      *ptr -= 32;
    }
    ptr++;
  }
  return string;
}

To use the touppercase() function, simply pass a pointer to the string you want to convert to the function as input. The function will return a pointer to the converted string.

Example of how to use the touppercase() function:

char string[] = "This is a test string.";

// Convert the string to upper case.
char *uppercase_string = touppercase(string);

// Print the converted string.
printf("%s\n", uppercase_string);

Output:

THIS IS A TEST STRING.