/*
  In this example, we are looking at the myriad ways that we can create a variable that holds a string and how their behavior differs.

  In all cases we are making use of "string literals" (text explicitly represented between "").
  
  To compile: gcc -o 06-strings 06-strings.c -Wall
  To run: ./06-strings
  
  
  C. Andrews
  2016-02-22
*/

#include <stdio.h>



int main(int argc, char * argv[]){
  // These thre create pointers that point to the string stored in read-only memory
  const char * str1 = "string1";
  char * const str2 = "string2";
  char * str3 = "string3";
  
  // these two populate arrays
  char str4[] = "string4";
  char str5[8] = "string5";

  
  printf("str1: %s\n", str1);
  printf("str2: %s\n", str2);
  printf("str3: %s\n", str3);
  printf("str4: %s\n", str4);
  printf("str5: %s\n", str5);
  printf("\n");


  // The first difference we find comes when we try to update a character in the string
  // The pointers are pointing to read only memory, so the strings can't be updated
  // Note that the use of const in str1 is saying that str1 points to a constant char *, so the compiler knows the string can't be changed
  // For the other two, the compiler doesn't know, so the program crashes when we try to access that memory
  //str1[0] = '*';  //assignment to read only memory
  //str2[0] = '*';  // segfault
  //str3[0] = '*'; // segfault
  str4[0] = '*';
  str5[0] = '*';

  printf("str1: %s\n", str1);
  printf("str2: %s\n", str2);
  printf("str3: %s\n", str3);
  printf("str4: %s\n", str4);
  printf("str5: %s\n", str5);
  printf("\n");      



  // The other thing we can try to do is point to a different string
  // str2 can't be changed because we declared it as const, so the compiler won't let us change its value (the address it points to)
  // here the const keyword is modifying the variable name itself, saying the value stored in this variable can't be changed,
  // as opposed to str1, which is a dynamic variable that points at a static string
  // str4 and str5 are arrays and we can't update the contents of an array this way
  
  str1 = "dalek1";
  // str2 = "dalek2";  //read only variable
  str3 = "dalek3";
  //str4 = "dalek4"; // can't assign to array
  //str5 = "dalek5"; // can't assign to array
  
  printf("str1: %s\n", str1);
  printf("str2: %s\n", str2);
  printf("str3: %s\n", str3);
  printf("str4: %s\n", str4);
  printf("str5: %s\n", str5);
  printf("\n");     
  return 0;
}