One of the hardest things you have to do is to keep track of three kinds of commands when writing and running computer programs. Those commands are:

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1 INTRODUCTION Your first daily assignment is to modify the program test.py to make it more friendly. But first, you need to learn how to edit programs quickly and efficiently. That means using the keyboard exclusively, forgoing the mouse. So if you find yourself reaching for the mouse, stop! An editor is a program that allows you to enter text into a file. Unlike word processors, such as Microsoft Word, editors are optimized for quickly and efficiently entering the text that makes up a computer program. Such program text is known as source code. In this class, you will use the editor named vim to efficiently place Python source code into a file. Python is a programming language and it is used to write computer programs. Computer programs that are written using text that Python understands are known as Python programs. One of the hardest things you have to do is to keep track of three kinds of commands when writing and running computer programs. Those commands are: system commands editor commands program commands System commands are the commands you enter into the terminal window to start things off. Editor commands are the commands used to interact with the editor when placing the text of a computer program into a file. Program commands are the actual lines of text in the computer program. Complicated, no? Don t worry. As with all things associated with writing computer programs, things become clearer and easier with practice. What you need to do now is, whenever you are instructed to issue a command, decide exactly what kind of command it is, system, editor, or program. LEARNING vim We ll start by learning the editor named vim. The easiest way to learn vim is to run the program vimtutor. To do so, boot your computer into Linux or UNIX and open up a terminal window. Then, in the terminal, run the command: vimtutor Note that the command vimtutor is a system command. It instructs your computer to run the program named vimtutor. The vimtutor program is a computer program that teaches you how to use the vim editor. You must learn the vim editor as your first quiz will question you on how to efficiently enter source code into a file using vim. Vim HIGH POINTS You will have noticed that vim, unlike say Microsoft Word, has two modes, insert and edit. The reason is that most programmers spend a vast majority of their time editing old code as compared to inserting new 1

2 code. By separating inputting and editing, the edit commands can be made very efficient, in terms of the keystrokes needed to accomplish a task. Consider deleting a line in vim versus Word. In vim, a simple dd, anywhere on the line, suffices. In Word, you must select a line with the mouse (not always easy to do), the switch to the keyboard and type control-x. There are keyboard shortcuts for Word that speed up selecting a line, but it still takes considerable effort to delete a line in Word. Remember these general rules: c means change lines and words d means delete lines and words x means delete character r means replace character h means go left (it is the leftmost of keys h, j, k, and l) l means go right (it is the rightmost of keys h, j, k, and l)? means search upwards (it is above /). repeats your last edit command i, I, a, A, o, O are insert commands the escape key gets you out of insert mode Note that the arrow keys and keys like Page-Up also work as expected. On the cs150 home page, there are links to other vim tutorials and a vim command cheat sheet. MODIFYING AN EXISTING PROGRAM Here is an example Python program: def main(): print("hello, world!") x = int(input("give me a number! ")) print(x+1,"is my favorite number!!") main() You can tell, using simple logic, that this program, when run, is likely going to say: hello, world! and then ask to be given a number. If 15 is given as the number, then it seems as if the program will then say that 2

3 16 is my favorite number!! Your task is to enter this program into a file named hello.py and test it. Next, you will modify it so that it asks for a name and then prints hello xxxxx, where xxxxx is the given name. It also should then say that its favorite number is the square of the given number rather than one more than the given number. Hint: the following code asks for and gets, then prints, a word: s = input("type a word: ") print("you typed", s) THE EDIT AND TEST CYCLE A very convenient way to change a program and see if your changes worked is to start a second terminal. Use the mouse (OK, we ll let you use the mouse just this once) and open up a second terminal window. You can switch between the two windows by typing Alt-Tab (hold the Alt key down, tap the Tab key, and release both). Practice switching until the keystrokes are swift and natural. In one windows, change to the cs150 directory. A directory is the same thing as a folder. Run these two commands to do so: cd cd cs150 Again, these commands are system commands. The cd command by itself says go to your top level directory. The cd cs150 command says move into the cs150 directory that hangs off the current directory. You will learn more on these kinds of commands in future activities. Now create a new directory called activities with the command: mkdir activities Move into this newly created directory by running the command: cd activities Now create a directory named vim and move into it (you should pattern match on what we did to create and move into the activities directory). If you did this right, running the command: pwd 3

4 should yield: /home/ubuntu/cs150/activities/vim or similar. Next switch to the other window and enter the command: cd /cs150/activities/vim The is an abbreviation for you home directory and the forward slashes separate directory names. Thus, this command says to change to the vim directory which hangs off the activities directory which, in turn, hangs off the cs150 directory which hangs off your home directory. Now, in one window, issue the command: vim hello.py This opens up a file named hello.py in which you can place the program. Make your changes and save the file with the command :w and don t forget to press the Enter key after the w. Note that you will not be exiting vim. In the other window (move to the other window using Alt-Tab, not the mouse, because the mouse is evil), type the command: python3 hello.py When you run this command, you should see something like: ubuntu@ubuntu: /cs150/activities/vim$ python3 hello.py hello, world! give me a number! is my favorite number!! ubuntu@ubuntu: /cs150$ Note that the text: ubuntu@ubuntu: /cs150/activities/vim$ is the system prompt; it also tells you that you are in the cs150/activities/vim directory, just like the pwd command would. The text: python3 hello.py 4

5 is the system command you type in response to the system prompt. The text hello, world! give me a number! is my favorite number!! is the output from the Python program hello.py as it is running; I typed in the number 41 and then pressed the Enter key to input the number. If you see an error in the output, switch to the other window and make any changes as necessary. After saving these changes, switch windows again and rerun the python3 command by tapping the up-arrow key once and then pressing the Enter key. Repeat the process until you get hello.py working correctly. Once it is working properly, try to change it so that it asks for a name and prints the square of the entered number. Once you do that, you should get an interaction like this: ubuntu@ubuntu: /cs150$ python3 hello.py What is your name? John hello John give me a number! is my favorite number!! ubuntu@ubuntu: /cs150$ If you can t get hello.py working properly, ask for help on the mailing list. You should successfully complete this activity before taking the first quiz and exam. 1 PREPARING FOR THE TEST Since you will not have internet access during your exams, run the linux command to download the course web pages: get.web This will create a directory named web that hangs off your home directory. For those of you on a Mac, you may get an error saying the command wget was not found. If so, run these commands: cd /bin curl -O troll.cs.ua.edu/cs150/wget chmod +x wget and then re-run the get.web command. Next, open your browser and then select File - Open File and browse to the file index.html that resides in the web directory. You will see a copy of the all the cs150 web pages. Be sure to bookmark the page with a tag named local. 5

6 To test that you did this correctly, disconnect from the internet and see if you can browse the pages using the local bookmark. You should, of course, be able to. SUBMISSION To submit your activity, make sure you are in the cs150 directory. Run the command: activity cs150 vim You will be asked for a guest password. Your instructor will give you the correct password in class. Note that when you type your password, it will look as if nothing is happening. Don t worry, something is. Press the Enter key when you are finished typing in the password. 6