Example C program to convert lower case into upper case and vice versa:

Below C program is used to convert lower case into upper case. strupr() function is a non standard function. So, all compilers may not support.

#include<stdio.h>

#include<string.h>

int main()

{

    char str[ ] = "Modify This String To Upper";

    printf("%s\n",strupr(str));

    return  0;

}

#include<stdio.h>

#include<string.h>

int main()

{

char str[ ] = "Modify This String To Upper";

printf("%s\n",strupr(str));

return 0;

}

Output:

MODIFY THIS STRING TO UPPER

Below C program is used to convert upper case into lower case. strlwr() function is also a non standard function. So, all compilers may not support.

#include<stdio.h>

#include<string.h>

int main()

{

    char str[ ] = "MODIFY This String To LOwer";

    printf("%s\n",strlwr (str));

    return  0;

}

#include<stdio.h>

#include<string.h>

int main()

{

char str[ ] = "MODIFY This String To LOwer";

printf("%s\n",strlwr (str));

return 0;

}

Output:

modify this string to lower

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