Example: C program to Remove all Characters in a String Except Alphabets

// C program to Remove all Characters in a String Except Alphabets
#include <stdio.h>

// It's the main function of the program
int main() {
    char sentence[1000];

    // Step-1 Take input sentence from User
    printf("Enter a Sentence: ");
    fgets(sentence, sizeof(sentence), stdin);

    // Step-2 Loop over the `sentence` variable to iterate each character of the sentence
    for (int i = 0, j; sentence[i] != '\0'; i++) {
        // Remove all the characters except alphabets
        while (!(sentence[i] >= 'a' && sentence[i] <= 'z') && !(sentence[i] >= 'A' && sentence[i] <= 'Z') && !(sentence[i] == '\0')) {
            // Accept only alphabet characters in the `sentence` variable
            for (j = i; sentence[j] != '\0'; j++) {
                sentence[j] = sentence[j + 1];
            }
            sentence[j] = '\0';
        }
    }

    // Step-3 Final output of the program
    printf("Filtered Sentence: ");
    puts(sentence);
    return 0;
}