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Problem Statement

A software company is developing a new online portal for its employees. During registration, every employee must create a Login Name. To maintain a consistent naming format, the company has decided that the login name should contain only alphabetical characters (A–Z or a–z). Numbers, spaces, and special characters are not allowed.

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Solution

#include <stdio.h>

int main() {
    char loginName[50];
    int i, valid = 1;

    printf("Enter Login Name: ");
    scanf("%s", loginName);

    for(i = 0; loginName[i] != '\0'; i++) {
        if(!((loginName[i] >= 'A' && loginName[i] <= 'Z') ||
             (loginName[i] >= 'a' && loginName[i] <= 'z'))) {
            valid = 0;
            break;
        }
    }

    if(valid)
        printf("Login Name Accepted.");
    else
        printf("Invalid Login Name! Only alphabets are allowed.");

    return 0;
}

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Input

Rahul

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Output

Login Name Accepted.