This error is bugging me!

The error is marked as a comment and in italics.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void initialize_number_generator(void);
void choose_new_secret_number(void);
main()
{
  char answer;
  int guess, secret_number, num_guesses = 0;
  printf("I have a number between 1 and 1000");
  printf("Can you guess my number?");
  printf("Please type your first guess");
  do {
    choose_new_secret_number();
    num_guesses++;
    printf("Enter guess: ");
    scanf("%d", &guess);
    if (guess == secret_number) {
      printf("You won in %d guesses!\n\n", num_guesses);
      return 0;
    } else if (guess < secret_number)
      printf("Excellent! You guessed the number!");
    printf("Would you like to play again (y/n)?");
    scanf(" %c", answer);
    printf("\n");
  } while (answer == 'y' || answer == 'Y');
  return 0;
} // end of main
void initialize_number_generator(void)
{
srand((unsigned) time(null)); // 'null' undeclared [first use this function]
} // end of initialize_number_generator
void choose_new_secret_number(int secret_number)
{
  secret_number = rand() % 1000 + 1;
} // end of choose_new_secret_number

In C++ a null value is used by the constant NULL. Capitalize it and the bug will go away, possibly to show different one.

You should change your #includes to the following:

<stdio>
<stdlib>
<time>
<math>

For all the standard includes the .h has been eliminated in C++. The .h extensions refer to the C style includes which could give you errors.

I added the math header becuase I beleive that the srand() fxn is located there and that is what seems to be giving you the problems.

u don't need the math header for srand()

but, u return a comment saying that u guessed the right number if the guess is less than the secret number

also, if u use the new c++ headers, write using namespace std right after the list of headers.

1) I'd recommend to call choose_new_secret_number() with an int& parameter, don't forget to inform the compiler before you use the function with this
declaration:
void choose_new_secret_number(int& secret_number);
2) If I guessed a 4 and the secret number was 5 the output would be
"Excellent ..." because of <else if(guess<secret_number)>
3) Write NULL instead of null
4) Don't forget to call the Initialize-function, !(declaration==execution);
5) good prog, though