Getting started

Refer to Lab 1 if you need a reminder about how to start Cygwin Terminal or Notepad++.

Start by downloading CS101_Lab05.zip, saving it in the directory H:\CS101.

Start a Cygwin Terminal and run the following commands:

cd h:
cd CS101
unzip CS101_Lab05.zip
cd CS101_Lab05

Reading and understanding code

One of the reasons that programming can be a challenge is the difficulty of debugging: figuring out why your program doesn't behave the way you expect, and modifying it so that it does.

An essential skill for debugging is being able to read code: looking at a program and figuring out what it does.

What you will do in this lab

For each of the code examples below, do the following:

1. Read the code example carefully.
2. Write down a prediction about what the code example will do when it is executed; specifically, what output will be produced.
3. Perform an experiment to determine the code's actual behavior by running it.
4. If your prediction matched the actual behavior, briefly explain what happened when the code was executed. If the actual results are different than your preduction, state a theory explaining the actual results.

Write down your predictions, experimental results, and theories in the file report.txt. You can use Notepad++ to edit this file.

For step 3, run the command make exampleN.exe, where N is the example number, then run the command ./exampleN.exe. E.g., for example 1,

make example1.exe
./example1.exe

Here is a complete example:

Example 1
Prediction: The output will be
   A
Experiment: The output produced was
   A
Explanation/Theory: Because the variable val contained the
value 20, the condition val >= 20 was true, and the "if"
block of the if/else statement was executed, and the "esle"
block was not executed.

Important: Before you leave, show your work to your instructor or a tutor.

Code examples

Example 1

int val = 20;
if (val >= 20) {
    printf("A\n");
} else {
    printf("B\n");
}

Example 2

int val = 20;
if (val > 20) {
    printf("A\n");
} else {
    printf("B\n");
}

Example 3

int val = 20;
if (val == 20) {
    printf("A\n");
} else {
    printf("B\n");
}

Example 4

int val = 20;
if (val = 20) {
    printf("A\n");
} else {
    printf("B\n");
}

Example 5

int val = 10;
if (val = 20) {
    printf("A\n");
} else {
    printf("B\n");
}

Example 6

int val = 0;
if (val = 0) {
    printf("A\n");
} else {
    printf("B\n");
}

Example 7

int val = 20;
if (val > 20) {
    printf("A\n");
}
if (val < 20) {
    printf("B\n");
}

Example 8

int val = 20;
if (val >= 20) {
    printf("A\n");
}
if (val <= 20) {
    printf("B\n");
}

Submit

To submit your work, type the command

make submit

Enter your Marmoset username and password (which you should have received by email.) Note that your password will not be echoed to the screen.

Important:

You must submit your work before leaving class. If you do not submit, you will not receive any credit for the lab.