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C program to check a given character is alphanumeric or not without using the library function

Here, we are going to learn how to check a given character is alphanumeric or not without using the library function in C programming language?
Submitted by Nidhi, on July 16, 2021

Problem statement

Given a character, we have to check whether the given character is alphanumeric or not without using the library function.

Program

The source code to check a given character is alphanumeric or not without using the library function is given below. The given program is compiled and executed using GCC compile on UBUNTU 18.04 OS successfully.

// C program to check a given character is
// alphanumeric or not without using library function

#include <stdio.h>

int isAlphaNumeric(char ch)
{
    if ((ch >= '0' & ch <= '9') || (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z'))
        return 1;

    return 0;
}

int main()
{
    char ch = 0;

    printf("Enter character: ");
    scanf("%c", &ch);

    if (isAlphaNumeric(ch))
        printf("Given character is an alphanumeric character\n");
    else
        printf("Given character is not an alphanumeric character\n");

    return 0;
}

Output

RUN 1:
Enter character: G
Given character is an alphanumeric character

RUN 2:
Enter character: 8
Given character is an alphanumeric character

RUN 3:
Enter character: +
Given character is not an alphanumeric character

Explanation

In the above program, we created two functions isAlphaNumeric() and main(). The isAplhaNumeric() function is used to check the given character is alphanumeric or not.

In the main() function, we read a character from the user and check given character is alphanumeric or not by calling the isAlphaNumeric() function and print the appropriate message on the console screen.

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