C isupper()

The isupper() function defined in the ctype.h header file. It helps to check the specified character is an uppercase alphabet (A-Z) or not.


int isupper(int argument); #where argument will be a character
 

isupper() Parameters:

The isupper() function takes a single parameter and is in the form of an integer and the return value should be an integer. When a character is passed it is converted into the integer value corresponding to its ASCII value.

Parameter Description Required / Optional
argument  The character to be checked Required

isupper() Return Value

 If the given character is an uppercase alphabet, isupper() returns a non-zero integer else zero. When an uppercase alphabet character is passed we will get a different non-zero integer.

Input Return Value
Zero If the parameter isn't an uppercase alphabet
Non zero number If the parameter is an uppercase alphabet

Examples of isupper() 

Example 1: Working of isupper() function in C


#include <stdio.h>
#include <ctype.h>
int main()
{
    char ch;

    ch='A';
    printf("If %c is passed to isupper(): %d", ch, isupper(ch));

    c='a';
    printf("\nIf %c is passed to isupper(): %d", ch, isupper(ch));

    return 0;
}

Output:


If A is passed to isupper(): 1
If a is passed to isupper(): 0

Example 2: How isupper() function works in C?


#include <stdio.h>
#include <ctype.h>
int main()
{
    char ch;

    printf("Please enter a character: ");
    scanf("%c", &ch);

    if (isupper(ch) == 0)
         printf("The given %c is not an uppercase alphabet.", ch);
    else
         printf("The given %c is an uppercase alphabet.", ch);

    return 0;
}

Output:


Please enter a character: H
The given H is a uppercase alphabet.