Here, we will read a lowercase character from the user and convert it into uppercase and print the result.

Program:

The source code to covert a lowercase character into uppercase without using the library function is given below. The given program is compiled and executed using GCC compile on UBUNTU 18.04 OS successfully.

// C program to convert a lowercase character
// into uppercase without using
// library function

#include <stdio.h>

char toUpperCase(char ch)
{
    ch = ch - 32;
    return ch;
}

int main()
{
    char ch;

    printf("Enter a lowercase character: ");
    scanf("%c", &ch);

    printf("Uppercase character is: %c\n", toUpperCase(ch));

    return 0;
}

Output:

Enter a lowercase character: q
Uppercase character is: Q

Explanation:

Here, we created two functions toUpperCase() and main(). The toUpperCase() function is used to covert the lowercase character to the uppercase character.

In the main() function, we read a lowercase character from the user and converted the entered character into uppercase using the toUpperCase() function.