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islower in C Programming

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The C islower function is one of the Standard Library Functions available in this C programming language. This function 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 used to check whether the character is a lowercase alphabet or not. The Syntax of the C islower function is.

islower(char)

The above islower function will accept a 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, it will return 0

islower in C Programming Example

The C islower method 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;

The following statement will ask the user to enter any character. And then we are using the scanf to assign the user entered a 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, 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");

The 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. It helps you know how to check whether the character is lowercase or not without using the islower function.