PC Labs in the Engineering Center
CR 235	CR 239
CR 244	CR 252 (24 hours)
CH 107	CR 244
Other campus sites are listed at www.colorado.edu/its/labs.

It is best to start a lab exercise during your assigned recitation period. If you run into any immediate problems, one of the instructors will be able to help. However, some of you might have missed your assigned time during the first week. If so, then you'll need to work on your own home machine or go to one of the PC labs on your own to get started.

Required Completion Date

This exercise must be completed as soon as possible after your first recitation. Otherwise you won't have time to complete the first homework (which is due the next week).

Set up Your University Account and Identikey

• If you are working in the university PC labs, you must first have a university account and identikey password. If you've already set these up, go to the next step. Otherwise, there are two methods to set up the account (as described in the handout Getting Started with Computing, available in ECCR 239):
  1. From any web-connected machine (including the ones in the first-floor lobby of the Engineering Center, just east of the revolving doors)
     • Press the return key, and you should get a small grey box. Then click on the "Set Identikey" button and follow the directions to set up your university PC account.
  2. Or you can visit the Information Technology Service Center on the first floor of the Telecommunications Building (two buildings east of the University Memorial Center). If you can't find them, telephone at 303-735-HELP. Bring your BuffOne card for identification.

  3. Now, whenever you use a university PC, your first task is to login through the Identikey system. Do this by pressing the return key to get the login screen, then type your login name and IdentiKey password. This will take you to the Windows work screen.

Starting Visual Studio

• We'll be using a software deveoplment system called Visual Studio. To start things up:
  1. Click on the Start button in the lower left corner of the screen.
  2. Click on All Programs
  3. Click on Microsoft Visual Studio 2005
  4. From the drop down menu, please choose Microsoft Visual Studio 2005
  Each program that you write will be part of a "Visual Studio Project", which is a group of files that will include the program you write (and other files that Visual Studio provides). Each project will reside in a directory (also called a "folder") that you create. For this exercise, you'll create a project called heatwave:
  1. Choose File-->New-->Project
  2. In the Project Type window, click on Visual C++. (You might have to first open the "Other Languages" option.)
  3. In the Template window, click on CLR Empty Project. (Later we will create more compilicated kinds of projects.)
  4. In the Name textbox, type the name: heatwave
  5. Please write down the path that's listed in the Location box. You'll need to know this location later when you save the files that you've created.
  6. Click the OK button.
  At this point, your project has been created and Visual Studio has created some of the files that every project requires. Next, you'll create one more file that contains your first C++ program, hooray!
  1. In the Solution Explorer window, RIGHT click on Source Files, choose Add, click on New Item.
  2. In the Templates window, click on C++ File (.cpp)
  3. In the Name text box, type the name heatwave.cxx --this will be the name of your first C++ program. Most programmers use ".cpp" for the file type of a C++ program, but we like to be a bit different, so please use .cxx instead!
  4. Click the Add button.
  The blank window that opened up is the spot where you would normally type your program. For this exercise, though, please highlight the following code in your browser (by clicking the left mouse button at the front of the code, dragging the mouse over the entire code block, then lifting up the mouse button. Then copy the code (Ctrl-C). Then go back to the blank window and paste in the code (Ctrl-V):

  //****************************************************************************
  // ABOUT THIS PROGRAM (heatwave.cxx)
  //   Written by: Michael Main, January 4, 2007
  //   Email address: main@colorado.edu
  //   Exercise for student: Irving Forbush
  //
  // INPUT: The program prompts the user to enter the height and radius of
  //   a tree. To make things simpler, we assume that the tree is a perfect
  //   cylinder.  The height is entered first (measured in feet), and then the
  //   radius is entered (also measured in feet).
  //   The program then prompts the user to enter the number of cubic feet of
  //   wood required to heat a house for one day.
  //
  // OUTPUT: The program calculates the number of days that the tree will heat
  //   a house, and outputs this value.
  //
  // EXAMPLE DIALOG:
  //   How tall is your tree in feet?
  //   13.2
  //   What is the radius of the tree in feet?
  //   2.1
  //   How many cubic feet of wood will heat a house for a day?
  //   40.2
  //   That tree will heat a house for 4.54921 days.
  //**************************************************************************
  
  #include <iostream>           // Provides cin, cout
  #include <cstdlib>            // Provides EXIT_SUCCESS
  using namespace std;
  
  const double PI = 3.14159;    // Defined to make the program readable
  
  int main () 
  {
      double height;            // Height of a tree in feet
      double radius;            // Radius of a tree in feet
      double requirement;       // Cubic feet of wood to heat house for a day
      double volume;            // Volume of the tree in cubic feet
      double days;              // Number of days that tree will heat house
  
      // Prompt user for input and read responses
      cout << "How tall is your tree in feet?" << endl;
      cin >> height;
      cout << "What is the radius of the tree in feet?" << endl;
      cin >> radius;
      cout << "How many cubic feet of wood will heat a house for a day?" << endl;
      cin >> requirement;
  
      // Computations
      volume = height * PI * radius * radius;
      days = volume / requirement;
  
      // Output days
      cout << "That tree will heat a house for " << days << " days." << endl;
  
      return EXIT_SUCCESS;
  }
  

  After you've pasted this material, please save your work with the command Ctrl-Shift-S.

  Compiling a C++ Program

  • The file that you copied is a C++ program that computes some information about heating a house, but the real purpose of the program is to demonstrate what a program looks like and how to run a program on a machine.

    Later, during your reading assignment, you can look at how this program was written. But for now you will simply see how to run a program such as this one. The first step in running a program is to run the C++ compiler. A compiler does the task of translating from a programming language (such as C++) to the low level instructions that a computer actually runs.

    To invoke our compiler for the current project, choose Build Solution from the Build menu.

  Running a Program

  After compilation, you'll now have an executable file called heatwave.exe. Later, we'll show you where to find this file. For now, though, we just want to run the program.

  To run the program that you've just built, choose Start without Debugging from the Debug menu. The program will run in a small window (though you may have to minimize Visual Studio to see that window.)

  Modifying the Program

  Go back to the Visual Studio window that contains heatwave.cxx. Spend one minute using the terminal's arrow keys to browse through the file. You can also use the keys to page down or page up. Each line of the file is part of a small C++ program. The lines near the top are comments indicating what the program does. One of these comments says that the program is an exercise for Irving Forbush. Use the backspace key to erase Irving's name and put your name instead.

  After you make this change, you may save the new heatwave.cxx (Ctrl-Shift-S).

  Six Pieces of C++

  The next step of this lab is to browse through heatwave.cxx a bit. Move through the program and find the following aspects:

  1. Comments in C++ are indicated by two slashes in a row. The entire line, after the // is a comment.

  2. The program has two include directives that include two C++ libraries:

     #include <iostream> // Provides cin, cout
#include <cstdlib> // Provides EXIT_SUCCESS

     These directive will appear in most every C++ program. The library iostream provides standard input and output functions and devices such as the standard input. The library cstdlib provides several other standard items such as a constant named EXIT_SUCCESS that our program uses. There is also a using directive indicating that the program will use the standard namespace, as discussed in class.

  3. After the directives, the program declares a double number named PI. But PI is no ordinary variable; it is a constant variable, declared as shown here:

     const double PI = 3.14159;

     A constant declaration, such as this, is a new feature of C and C++. They are like ordinary variable declarations that are given an initial value, but because they are declared as a const, the compiler will prevent you from writing any statements that change the value of this variable. In this class, our programming style requires the names of all constants to be written in capital letters, allowing constants to be easily spotted.

  4. Search through the code and find the heading of the main program, which begins with the words "int ". The word int indicates that the main program computes an integer value and returns this value to the Windows operating system. This may be different than your textbook--many programmers simply declare the main program as a void function (which means that it does not give any final value back to the operating system). But we suggest that your main program returns an int value, since this integer can be used to tell the operating system whether the program was successful or not. For our compilers, a main program returns the number 0 to indicate successful termination. For our g++ compiler, this "successful return value" is defined in cstdlib as a constant called EXIT_SUCCESS. Can you find the return statement in heatwave's main program, which indicates successful termination? (Be warned: older compilers on our DEC machines don't define EXIT_SUCCESS. If you are using an older machine some day, you can still compile by adding the string -DEXIT_SUCCESS=0 immediately after the g++).

  5. Some output is quite simple in C++. A basic output statement looks like this:

     cout << "How big is your tree?" << endl;

     The name cout is the "console output device"--the screen. The operator << is the output operator. So this statement sends the string "How big is your tree?" to the console output device, and then the special object, endl, is sent to the console output device. The object endl is an end-of-line, and it also serves to "flush" the output (meaning that the output will be written then and there, rather than waiting for some output buffer to fill up).

  6. Some input is also quite simple in C++. A basic input statement looks like this:

     cin >> radius;

     The name cin is the "console input device"--the keyboard. The operator >> is the input operator. So this statement inputs a real number into the variable radius. You'll learn a lot more about input/output in other labs, but this will do for now.

  Finding Compilation Errors

  Let's put a compilation error into the heatwave.cxx file. Go down to the input line "cin >> height;" and delete the semicolon at the end of the line. This is certainly an error! Move the cursor away from this error before you proceed to the next paragraph.

  Now, compile the program again. A small Error List window will open up indicating that the program has a problem that prevents compilation. If you double click on any error message, then the cursor jumps to the location where the compiler detected the error.

  Often, the location where an error was detected is slightly after the actual error. So, to find the error, start at the cursor and scan backward. Go ahead and fix this syntax error now, and save the file before moving to the next step.

  Modifying the Heatwave Program
  • The heatwave program prints its answer in days. In order to show you how to modify a program, we'll add weeks to the answer. At this point you still don't need to understand how the program is working--it is enough to just understand how to modify a program in the way that these steps describe.

    For the first modification, move to the top part of the program and find the lines shown here:

        double height;            // Height of a tree in feet
        double radius;            // Radius of a tree in feet
        double requirement;       // Cubic feet of wood to heat house for a day
        double volume;            // Volume of the tree in cubic feet
        double days;              // Number of days that tree will heat house
    

    These lines tell the program to use memory locations to keep track of various computational values. We'll tell the program to keep track of one more value, the approximate number of weeks that the tree will heat the house. To do this move the cursor to the end of these lines--somewhere after the words " will heat house". You can move the cursor here with the arrow keys, or by moving the mouse to the location and clicking the left button. Once the cursor is here, press return, which will open up a new line. On the new line, please type:

    int weeks;                // Number of whole weeks that tree will heat house
    

    Try to align your new line with the rest of the program, aligning front of each line, and aligning the slashes (which indicate the start of a comment that is meant to be read by a person).

  • For the second modification, find these lines:

        // Computations
        volume = height * PI * radius * radius;
        days = volume / requirement;
    
        // Output days
        cout << "That tree will heat a house for " << days << " days." << endl;
    

    Add the two new lines shown here:

        // Computations
        volume = height * PI * radius * radius;
        days = volume / requirement;
        weeks = (int) days / 7;
    
        // Output days
        cout << "That tree will heat a house for " << days << " days." << endl;
        cout << "Which is " << weeks << " whole weeks." << endl;
    

    The first new line calculates the number of whole weeks by dividing the days by 7. The second new line prints this number of whole weeks.

    Now save and recompile the program. After recompilation, run the program again You might be surprised to see that the number of whole weeks was rounded down. This rounding down to a whole integer occurs whenever a fractional value is assigned to an integer variable.

  Saving Your Work
  • Shut down Visual Studio and open the My Computer window. Within this window, move down to the Location that you remembered when you created the project. Within this location, there is a folder called heatwave. In order to save your work, it is best to save this entire directory. You can copy this directory to a USB drive or to an external file storage system such as CU's Webfiles system at www.colorado.edu/its/webfiles/started.html.