• Due before class on Wednesday, March 1
• This homework contains code to be submitted electronically. Put your code in a folder called hw18 and submit using the 204sub command.
• This is an electronic homework and you do not need to print out anything to turn in during class.

Assignment

1. Required reading: Sections 4 (Recursion) and 5 (The structure of multi-file programs) from the Unit 5 notes,
2. Here is a program with a #include statement for a header file that you will complete:

   #include <stdio.h>
   #include "countdown.h"
   
   int main() {
     int n;
     do {
       printf("Enter n: ");
       fflush(stdout);
     } while (scanf(" %d", &n) != 1);
   
     // this calls the function YOU have to write!
     countdown(n);
   
     return 0;
   }

   (You can download that file from this link.)

   You may not change that program! Instead, you need to make a header file countdown.h and a definitions file countdown.c that contain (respectively) the prototype and definition for the countdown function.

   The countdown function should have the following prototype:

   void countdown(int n);

   that prints out the numbers from n down to 1 and then prints out the message "hooray!". For example, calling countdown(6); should result in

   6
   5
   4
   3
   2
   1
   hooray!
   

   You are strongly encouraged to write the countdown function recursively! Here is a complete example of compiling and running your program:

   roche@ubuntu$ gcc countdown.c main.c -o main
   roche@ubuntu$ ./main
   Enter n: 3
   3
   2
   1
   hooray!