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islower in C Programming

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The C islower() function is one of the Standard Library Function available in this C programming language. This function is used to check the given character is a lowercase alphabet or not. Let us see how to use islower in C Programming language with example.

C islower Function syntax

In C Programming, islower is a built-in function present in the header file which is used to check whether the character is lowercase alphabet or not. The Syntax of the C islower function is.

islower(char)

The above islower function will accept single character as the parameter, and check whether the given character is in lowercase or not.. The islower function will return an integer value as output.

  • If the character inside the islower function is in lowercase then it will return non zero value
  • If the character inside the islower function is not in lowercase then it will return 0

islower in C Programming Example

The C islower method is used to find whether the given character is a lowercase character or not.

This C program allows the user to enter any character, and check whether the character is between a to z using the islower function.

//Example for islower in C Programming
#include <stdio.h>
#include <ctype.h>

int main()
{
    char ch;
    printf("Please Enter Any Lowercase Character: \n");
    scanf("%c", &ch);

    if(islower(ch))
    {
      printf("\n You have entered a Lowercase Character");         
    }
    else
    {
      printf("\n %c is not a Lowercase Alphabet", ch);
      printf("\n I request you to enter Valid Lowercase Character");	
    }
}

OUTPUT

islower in C Programming 1

Let me enter the Uppercase letter

islower in C Programming 2

ANALYSIS

First we declared a character variable called ch

char ch;

Following statement will ask the user to enter any character. And then we are using the scanf to assign the user entered character to ch variable

printf("Please Enter Any Lowercase Character: \n");
scanf("%c", &ch);

In this next line, we added the If Statement to check whether the character is between ‘a’ and ‘z’ or not using C islower function. If the condition is True then the following statement will print

printf("\n You have entered a Lowercase Character");

If the above condition is FALSE then the given character is not a lowercase Alphabet. So, it will print below statements

printf("\n %c is not a Lowercase Alphabet", ch);
printf("\n I request you to enter Valid Lowercase Character");

Above code will definitely check whether the given character is a lowercase character or not, but what if, we enter the numeric value

islower in C Programming 3

TIP: Please refer C Program to check whether the Character is Lowercase or Not article to understand, How to check whether the character is lowercase or not without using the islower function.