CS 101
Lab 6

Objectives

• Learn basic operation of Eclipse
• Using the newly developed knowledge, write, compile, and debug your first C program

Instructions

Using Eclipse

Creating a Project

• First, run Eclipse from the Applications menu under Programming.
• If asked about a Workspace, just click "Ok". Now, you should see the Eclipse environment as shown in the figure below.
• Next, create a new C project by following these steps:
• Goto "File" menu, select "New", and then "New Project". You can refer to the figure below as a guide to locate the "New Project" menu item.

  

• Double click on "C" and double click on "Managed Make C Project".
• Name the project "lab6" (without quotes) and click "Next".
• Click "Finish".
• If asked whether to use the C/C++ Perspective, choose "Yes".
• Locate the "lab6" project on the left side of Eclipse.
• Right click on the "lab6" project and choose "New", then "Source File"
• Name your file "intro.c"

Entering the code

• Locate the "intro.c" tab in the center of your screen.
• Type in (or copy and paste) the following C program and save it:

If you've programmed in C before, you may notice that there's an error in the code. This is done on purpose to show you what happens when you make a mistake while programming. Use the tab key to automatically indent properly.

#include <stdio.h>

int main(void)
{
   int x = 0;

   printf("Enter a number: ");
   scanf("%i", x);

   if (x % 2)
      printf("%i is odd\n",x)
   else
      printf("%i is even\n",x);

   return 0;
}

 

• Once you finish typing, save your file by clicking on the Save button in the toolbar.
• When you save, Eclipse compiles your project and shows you any error messages.

Fixing the errors

• Locate the error underlined in red.
• To see the error message, point your mouse cursor at the underlined text.
     Write down what happens on your answer sheet.
          1. Write the warning and error message or messages that Eclipse produced:
  
• Fix the mistake.
• Save again.

Running your program

• Locate the "Run" button on the toolbar (A Green Circle with a white Play arrow inside). The "Run" button is shown is the figure below.

  

• If you see a small drop down menu, Click "Run...". Now, you should see a dialog as shown in the figure below.
• Double click on "C/C++ Local Application".

  

• Click the "Search Project" button to see the dialog shown below.

  

• Click "Ok"
• Click "Run"
• Click in the tab called "Console" at the bottom of the window.

Your program will ask you to enter a number. Type in any number and hit enter.

Write down what happens on your answer sheet.
2. Write what happens when you run your program for the first time after it compiles:

Oops, it looks like we have another problem with our program, and the compiler didn't catch it.

It seemed to happen just after entering the number, so let's look at the line where our program reads the input.

scanf("%i", x);

(Notice that the scanf line is underlined in yellow. Read the warning message by pointing your mouse at the underlined code.)

The problem is that this function expects to be given the location of an integer, but we gave it the integer itself. Since the value of a was zero, the function tried to use memory at location 0, which caused a segmentation fault. (and no output in Eclipse.)

To fix the error, we put a & in front of the variable x.

scanf("%i", &x);

Save and run your program again by clicking the green part of the "Run" Button.