c program to remove characters in string except alphabets

if you enter any string then it removes all character from string except alphabet.

#include<stdio.h>

int main()

{

    char line[150];

    int i, j;

    printf("Enter a string: ");

    gets(line);

    for(i = 0; line[i] != '\0'; ++i)

    {

        while (!( (line[i] >= 'a' && line[i] <= 'z') || (line[i] >= 'A' && line[i] <= 'Z') || line[i] == '\0') )

        {

            for(j = i; line[j] != '\0'; ++j)

            {

                line[j] = line[j+1];

            }

            line[j] = '\0';

        }

    }

    printf("Output String: ");

    puts(line);

    return 0;

}