string without digits

#include<stdio.h>
#include<string.h>
int main()
{
    char str[150];

    int i, j;

    printf("Enter the string with digits\n");

    gets(str);

    for(i = 0; str[i] != '\0'; ++i)
    {
        while (!( (str[i] >= 'a' && str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z') || str[i] == '\0') )
        {
            for(j = i; str[j] != '\0'; ++j)
            {
                str[j] = str[j+1];
            }
           str[j] = '\0';
        }
    }
    printf("The string after deleting the digits\n");

    puts(str);

    return 0;
}
//Happy Coding