Why am I getting a segmentation fault in c? : I am getting segmentation error when trying to do the CS50 Crack cryptography problem. I am a novice in C language. The code compiles Ok but when I run the debugger it seems to get the following error: 
Process received SIGSEGV: Segmentation fault
...at guess[0] = *alphabet1;
I have looked at other stack overflow questions and suspect it could have something to do with string guess being a string literal but this has has muddied the waters for me. Can you please explain me why I am getting segmentation error or direct me to a good webpage to research this. The pertinant code is below. Thanks in advance for any help.

    string guess= "     ";
    string hashed_word= "     ";
    string letters=
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ";
    string letters1= 
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    char *alphabet;
    char *alphabet1;


    //check a-Z
    for (int j = 0; j < 52; j++)
            {
                alphabet1 = &letters1[j];
                guess[0] = *alphabet1;
                hashed_word = guess;
                if (strcmp(hashed_word, s) == 0)
                {
                      print(guess);
                }
            }