CPS109 Lab 1. i. To become familiar with the Ryerson Computer Science laboratory environment.

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1 CPS109 Lab 1 Source: Partly from Big Java lab1, by Cay Horstmann. Objective: i. To become familiar with the Ryerson Computer Science laboratory environment. ii. To obtain your login id and to set your password. iii. To learn how to send mail and how to forward mail from your scs account to your matrix account. iv. To edit, compile and run your first java program in linux and in an IDE. v. To recognize syntax and logic errors. Instructions: 1. The operating system takes care of much of the filing work --storing, moving, and remembering where things are--so you can do useful things at a higher level. You interact with the operating system via a Graphical User Interface (GUI), for example a windowing system using a pointing device like a mouse, or a Command Line Interface, using only a keyboard and a single window. Operations such as browsing the Web and editing text in a word-processing program involve the operating system executing a program. The operating system itself is a program that is running all the time. It executes your instructions and, in turn, it can run other programs. It is useful to think of a program as a sequence of instructions. Both executable instructions and digital data can be represented as files, for example, on your hard drive. Both are sequences of symbols, just like the letters that make up the words in this sentence. Your job as a programmer is to provide the instructions for new programs. 2. The TAs will show you how to logon and to set your passwords for both the linux operating system and the Windows operating system. Learn how to switch from one system to the other. The Administrators and TAs will also tell you how to read and send on the SCS system. The Department of Computer Science (instructors and administrators) send to your scs account, so it is very important that you receive and read on that account. If you want your scs to be forwarded to your matrix account, you can create a ".forward" file for that purpose. For example if your matrix userid is first.lastname, then you can create the.forward file with the following command issued in your home directory. cd echo 'first.lastname@ryerson.ca' >.forward This causes the file.forward to have the single line first.lastname@ryerson.ca and subsequent sent to yourscsuserid@scs.ryerson.ca will be forwarded to first.lastname@ryerson.ca. Send an to yourself to verify that it works. 3. On the linux operating system, familiarize yourself with the basic commands, such as: a) ls... to list the contents of a directory

2 b) mkdir cps109...to make a directory for cps109 c) cd cps to change to that directory d) mkdir lab1 e) cd lab1 2. pico Hello.java... to create and edit a file called Hello.java. Type in the following simple program. Look at the commands at the bottom of the editor to see how to save the file and exit. public class Hello public static void main(string[] args) System.out.println("Hello") ; a) javac Hello.java... to compile the above file 3. If it compiled without errors, then use the ls command to see what files you now have. You should find a Hello.class file which is the "byte code" of your compiled program. If the program did not compile, then use the editor again to fix mistakes, save and compile again. 4. java Hello... to run the above file 5. cp Hello.java HelloWorld.java...to make a copy of your program 6. pico HelloWorld.java... to edit and alter your program, so that now it says "Hello World". When you try to compile, you may have difficulty. Check if you changed the class name to match the file name. 7. Compile and run the latter program to see that it works. 8. rm Hello.java... to remove Hello.java 9. ls... Note you still have Hello.class, and you can still run it. 10. rm Hello.*... will get rid Hello files with any suffix. 11. cat HelloWorld.java to see a typing of the file 12. cat HelloWorld.java > temp types HelloWorld and sends the output to the file temp. 13. cat HelloWorld.java >> temp types HelloWorld and appends the output to the file temp. 14. cat HelloWorld.java >> temp types HelloWorld and appends the output to the file temp again. 15. less temp to see a listing of the file in a window where you can advance by hitting the space bar or the enter key, and you can go back a window using the b key. Type "/class" to look for the word class, and press n to move to the next occurrence. Use less when you want to look at a file without modifying it. 16. emacs temp to open a more powerful editor than pico. While in this editor, hold down the control key and press h, then press the t key (without the control key), and you should see the emacs tutorial. Go through some of this tutorial to learn basic commands in emacs. If you want to go back to temp and try some commands there, press "control-x b enter". To leave emacs: "control-x contol-c". 17. emacs HelloWorld.java &...use commands that you learned from the tutorial for

3 copying the line of code that prints the message, so that it will be printed three times. Save the file "control-x control-s", and then compile and run it in the terminal window. When you are done experimenting with emacs, you can exit using the File menu or using the contol-x control-c command. 18. cp HelloWorld.java Hello.java...to make another copy of this program. 19. Switch back to the Windows environment, and find the BlueJ icon (a blue jay). Start this integrated development environment (IDE). Open a browser and direct it to the following url which contains a tutorial on the use of BlueJ. Read Sections 3 and 5 of this tutorial to learn how to open an existing project and how to create a new project. (For these instructions, we will assume you are using this IDE, but you may use another of your own choice). 20. The program that you'll be running to write computer programs is your text editor, which sometimes is part of an integrated compiler environment, such as BlueJ. Click on Project in BlueJ and choose New Project. Choose a location for the new project directory and give it the name Hello. Click on Create. In the resulting window, click on New Class... and give it the name Hello with the default Class type of Class. Click on Ok. You will see a box appear with the title Hello. Double click on that box to bring up an editor for the class. BlueJ provides an outline of potential code for the class. Select the code using the mouse and replace it with code that you type identical to the code in Step 4. Click on the Compile button at the top, and notice that the box representing your class changes from striped to clear, indicating that it is compiled. Remove a quote mark from around Hello, and press Compile again. Notice that the box for your Hello class remains striped and in the editor the line with the error is highlighted. Fix the error and re-compile. To run the program, right-click on the Hello box and choose the method void main(string[] args). Click on OK in the resulting pop-up, and you should see a Terminal Window pop up with the print out of Hello. Change the program to print out Hello BlueJ, and run it again. 21. Frequently in these labs you will be asked to compile a sample program. Below is a copy of a Java program that displays a drawing. Open another New Class called Art. Double click on the box for the Art class to bring up the BlueJ editor. Copy and paste the program below into the text editor to replace the code that is there. Compile and run the program. /** Displays an 'art' drawing */ public class Art public static void main(string[] argv) String s1 = " * * * * * * "; String s2 = " * * * * * "; String s3 = " \\n"; String s4 = " \\n"; System.out.print(s4 + s1 + s3 + s2 + s3);

4 System.out.print(s4 + s4 + s4 + s4 + s4); 22. Writing Simple Programs Your initial Java programs will be contained entirely in one file. There are some elements that all the programs will share because of the requirements of the Java language. When you build a program, your compiler looks for code of the form: public class Classname public static void main(string[] args) /* your work goes here */ 23. Detecting Syntax and Logic Errors There are numerous opportunities for error in any program, often times in places that seem too simple to require close attention. What do you think the following program is designed to do? public class Cube public static void main() double height = 3.0; \ inches double cube_volume = height * height * height; double surface_area = 8 * height System.out.println("Volume = " cube_volume); System.out.println("Surface area = " + surface_area; Will it work as shown? If not, what problems can you identify? Make a new class and try compiling the program. Fix the syntax errors. The program has two logic errors. Fix them and save the corrected program. 24. Exercise P1.1 from the end of Chapter 1 in Big Java. Write a program NamePrinter that displays your name inside a box on the console screen, where the top and bottom of the box are obtained by printing a line like , and between those two lines you print your name, like Dave.

5 What to hand in. Put your answers to the last two steps, including programs that you wrote, into one ASCII text file called lab1.txt (i.e., it should be readable with the command less lab1.txt). Submit this file to your TA according to the TA's instructions.