isalpha() and isdigit() functions in C/C++ with example

2.3

isalpha(c) is a function in C which can be used to check if passed character is an alphabet or not. It returns a non-zero value if it’s an alphabet else it returns 0. For example, it returns non-zero values for ‘a’ to ‘z’ and ‘A’ to ‘Z’ and zero for other characters.

Similarly, isdigit(c) is a function in C which can be used to check if passed character is a digit or not. It returns a non-zero value if it’s a digit else it returns 0. For example, it returns non-zero value for ‘0’ to ‘9’ and zero for others.

Example Problem : Given a string str, find the number of alphabetic letters and number of decimal digits in that string.

Examples:

Input: 12abc12
Output: Alphabetic_letters = 3, Decimal_digits = 4

Input: 123 GeeksForGeeks is Number 1
Output: Alphabetic_letters = 21, Decimal_digits = 4

Explanation And Approach:

// C program to demonstrate working of isalpha() and
// isdigit().
#include<stdio.h>
#include<stdlib.h>

int main()
{
    char str[] = "12abc12";

    int alphabet = 0, number = 0, i;
    for (i=0; str[i]!= '\0'; i++)
    {
        // check for alphabets
        if (isalpha(str[i]) != 0)
            alphabet++;

        // check for decimal digits
        else if (isdigit(str[i]) != 0)
            number++;
    }

    printf("Alphabetic_letters = %d, "
           "Decimal_digits = %d\n", alphabet, number);

    return 0;
}

Output:

Alphabetic_letters = 3, Decimal_digits = 4

This article is contributed by Mazhar Imam Khan. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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