Modular Reusable Code Example in Function

Program to check if it is upper or lowercase if it is then print it or if it is not then change it on the lower or upper

Code:

#include<stdio.h>

int is_lower_case(char);
int is_upper_case(char);
char to_upper_case(char); //uppercase quivalent of lowercase or uppercase as it is
char to_lower_case(char); //lowercase equivalent if uppercase or lowercase will print

char to_lower_case(char ch)
{
    if(is_upper_case(ch))
    {
        return ch+32; //if it  is uppercase then we are making it to the lowercase by adding 32
    }
    else
    {
        return ch;
    }
}

char to_upper_case(char ch)
{
    if(is_lower_case(ch))
    {
        return ch-32;
    }
    else
    {
        return ch;
    }
}

int is_lower_case(char ch)
{
    if(ch>='a' && ch<='z')
    {
        return 1;
    }
    else
    {
        return 0;
    }
}

int is_upper_case(char ch)
{
    if(ch>='A' & ch<='Z')
    {
        return 1; //1 means by default true in c
    }
    else
    {
        return 0; //0 means by default false
    }

}


int main()
{
    char k,p;
    p='A';
    k=to_lower_case(p);
    printf("Lower case equivalent of %c is %c\n\n",p,k);

    p='p';
    k=to_upper_case(p);
    printf("Upper case equivalentof %c is %c\n",p,k);

    return 0;

}

Output:

Lower case equivalent of A is a

Upper case equivalentof p is P