Lab 2: Prime Numbers

Table of Contents

• Lab 2: Prime Numbers

  • Overview

  • Task 1: Create a bool.h file

  • Task 2: Create your Prime Function

  • Task 3: Test Random Generated Numbers

You will learn about preprocessor directives in C.

Read These Pages:

• https://www.javatpoint.com/c-preprocessor

• https://www.tutorialspoint.com/cprogramming/c_preprocessors.htm

• https://www.tutorialspoint.com/cprogramming/c_header_files.htm

• https://docs.microsoft.com/en-us/cpp/preprocessor/hash-if-hash-elif-hash-else-and-hash-endif-directives-c-cpp?view=vs-2019

Note

You will need to install a GCC compiler on your computer.

• See Windows 10: Setup C Environment on how to set up Windows 10 to compile and execute C.

• Don’t know if you have GCC installed? Open a prompt and run command:

  gcc --version
  
  # Ubuntu shell Output
  user@DESKTOP-Z4T37ER:~$ gcc --version
  gcc (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0
  Copyright (C) 2017 Free Software Foundation, Inc.
  
  # Windows CMD Output
  C:\Users\user>gcc --version
  gcc (MinGW.org GCC-8.2.0-3) 8.2.0
  Copyright (C) 2018 Free Software Foundation, Inc.
  

Overview

You will create a C program that determines if a given number is a prime number.

A prime number is a a whole number that cannot be made by multiplying other whole numbers. less than or equal to n:

Task 1: Create a bool.h file

C does not have a native bool type, there is a library called stdbool.h that offers that functionality. Instead of using it, let’s build our own!

Note

After this exercise, the safest option is to use stdbool.h :) This activity provides an example of how to create a simple .h file that contains a custom data type.

Traditional programing treats a 0 as FALSE and 1 as TRUE. However, any non-zero value in C is TRUE, and only 0 is FALSE. That means that expressions like int a = -8 and int = 2350 are evaluated as TRUE.

1. Read the discussion on on Using boolean values in C on Stack Overflow.

2. Choose option of creating your bool type.

3. Create file called mybool.h

4. Create a new data type, such as my_bool

Task 2: Create your Prime Function

1. Start with the command line template from C Templates.

2. Include your mybool.h file:

   #include "mybool.h"
   

   1. Verify that your file compiles without any errors or warnings.

   2. See How to write your own header file in C for additional information.

3. Pass the value in using the command line

4. Create a function with this prototype (or using your own type):

   my_bool number_is_prime(int);
   

5. Develop the function. You can use Google to help you.

6. Print the result in main() if the number is prime or not

Task 3: Test Random Generated Numbers

1. Implement a random number algorithm using https://www.geeksforgeeks.org/rand-and-srand-in-ccpp/

2. Use the #define macro to set the maximum number of random numbers to find. https://www.programiz.com/c-programming/c-preprocessor-macros

   #define MAX   25
   
   int main() {
   . . .
   for (i = 0; i < MAX; ++i)
   {
       // get random number
   . . .
   

3. Generate 25 numbers in a loop, test each number for prime.

4. Were any numbers prime?

5. If not, increase the value till you find one!