Using functions islower, isupper, tolower, toupper : char function « Data Type « C Tutorial

1. C Tutorial
2. Data Type
3. char function

#include <stdio.h>
#include <ctype.h>

int main()
{ 
   printf( "%s\n%s%s\n%s%s\n%s%s\n%s%s\n\n",
           "According to islower:",
           islower( 'p' ) ? "p is a " : "p is not a ",
           "lowercase letter",
           islower( 'P' ) ? "P is a " : "P is not a ",
           "lowercase letter",
           islower( '5' ) ? "5 is a " : "5 is not a ",
           "lowercase letter",
           islower( '!' ) ? "! is a " : "! is not a ",
           "lowercase letter" );

   printf( "%s\n%s%s\n%s%s\n%s%s\n%s%s\n\n",
           "According to isupper:",
           isupper( 'D' ) ? "D is an " : "D is not an ",
           "uppercase letter",
           isupper( 'd' ) ? "d is an " : "d is not an ",
           "uppercase letter",
           isupper( '8' ) ? "8 is an " : "8 is not an ",
           "uppercase letter",
           isupper( '$' ) ? "$ is an " : "$ is not an ",
           "uppercase letter" );

   printf( "%s%c\n%s%c\n%s%c\n%s%c\n",
           "u converted to uppercase is ", toupper( 'u' ),
           "7 converted to uppercase is ", toupper( '7' ),
           "$ converted to uppercase is ", toupper( '$' ),
           "L converted to lowercase is ", tolower( 'L' ) );

   return 0;

}

According to islower:
p is a lowercase letter
P is not a lowercase letter
5 is not a lowercase letter
! is not a lowercase letter

According to isupper:
D is an uppercase letter
d is not an uppercase letter
8 is not an uppercase letter
$ is not an uppercase letter

u converted to uppercase is U
7 converted to uppercase is 7
$ converted to uppercase is $
L converted to lowercase is l