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Grinnell’s GNU/Linux Environment

Summary
We examine the operating system environment in which the course is conducted.

Introduction

As this is a workshop-style course (a.k.a. a constructivist, collaborative, computing course), on most class days you will find yourself working on the computers in our classroom. You will quickly discover that while these computers have many similarities to the computers you have used in the past, there are also some differences. (When we started teaching this course, many students hadn’t used computers at all and we had to teach things like how to use a Web browser and what the Web was. You will occasionally find comments in the readings and labs that reflect that different perspective.) In this document, we will explore some of the key issues you may need to consider in working on the GNU/Linux computers that we prefer in computer science.

Operating Systems and Graphical User Interfaces

A modern computer is much more than a bunch of circuitry. Most of us think of computers in terms of the operating system that they run and the graphical user interface that accompanies the operating system. Those terms may be new to you, so let us consider them briefly.

As its name suggests, an operating system (also “OS”) is the system used for operating the computer. It is a large computer program that manages and simplifies most of the underlying hardware. The operating system is responsible for managing files, managing other programs, dealing with the keyboard, screen, and other peripherals, and much more.

In the old days of computing (e.g., when when the more senior of the CSC 151 instructors started programming), you interacted with the operating systems almost exclusively by typing on a keyboard and seeing results on a screen (yes, we had evolved beyond punchcards). There was no mouse. To us, the operating system really referred to the underlying capabilities.

These days, you interact with computers through a graphical user interface (also “GUI”). Its name is similarly clear: It’s the interface through which you use the computer, and it’s a graphical (as opposed to textual or auditory) interface. Modern graphical user interfaces stem from work at Xerox PARC, although they were introduced to the broader consumer world through the Apple Macintosh. To most modern users, the GUI is indistinguishable from the OS. (Programmers may still find it useful to distinguish between them.)

The GNU/Linux Operating System

In Grinnell’s computer science department, we use an operating system called GNU/Linux. GNU/Linux is distinguished by being an Open operating system, which means that anyone who has the knowledge and desire to make modifications to the program code of the operating system is permitted to do so, and a Free operating system, which means that it doesn’t have to cost you anything to install it on your computer, in contrast to the Macintosh OS, which used to have a list price of about $100, or the Microsoft Windows OS, which still has a list price of about $100. In fact, the GNU/Linux community uses “Free” in two ways, in the way we used it above (as in “Free Lemonade”) and in the way we used “Open” (as in “Freedom”).

Why do we use GNU/Linux rather than Macintosh OS or Windows, particularly since ITS seems to prefer Windows? One reason is that we consider GNU/Linux to be technically superior: It is less likely to crash, it is freer from viruses and other irritants, it has a much longer history of separating what the average user can do from what the administrator can do. More importantly, it is much more portable. You can sit down at any GNU/Linux computer on our network and have exactly the same set of files naturally available. (Think about how many times you save a file on one Windows box on campus, forget to move it to StorageServer, and then cannot access it elsewhere on campus. That will never happen on the GNU/Linux network.)

Many members of the department also have a philosophical preference for the Open Source and Free Software movements, of which GNU/Linux is an important part. We believe that good software should be free, in both senses of the word.

Xfce

GNU/Linux, unlike Macintosh OS X or Microsoft Windows, permits you to use a variety of GUIs on top of the same underlying OS. Our system administrator has chosen to use a GUI called Xfce as the default. Our experience suggests that Xfce provides an appropriate balance of power, configurability, and usability.

Xfce, like Microsoft Windows, provides a task bar at the bottom of the screen. You will click icons on the task bar to start applications. You may use a popup menu on the task bar to “log out” when you are done with your work.

If you want to explore other GUIs (sometimes called Window managers), you can select your GUI when you log in to the MathLAN. Do so with caution, as some Window managers are very strange, and it may be difficult to figure out how to escape from them.

If you are interested, you can also find many ways to modify Xfce, such as moving the task bar elsewhere.

Using GNU/Linux

So, what does this all mean for you, other than that the computer scientists at Grinnell worry about these things? It means that you will have to use an unfamiliar GUI in this course and in most future computer science courses you take. Fortunately, our configuration of Xfce is similar enough to other operating systems, particularly to Microsoft Windows, that you should find it fairly natural to use.

Like the Microsoft Windows workstations on campus, the GNU/Linux workstations require you to log in to use them. Our GNU/Linux network uses an independent password system, so you should remember that you have different passwords (unless you take the time to make them the same). In contrast to passwords on the Windows network, GNU/Linux passwords are stored in such a way that no one, not even the system administrator, can extract the original password, so it is safe to use the same password. (Of course, someone trying to guess your password still has an opportunity to do so.)

Important GNU/Linux Programs

In this course, you will be using a variety of programs. There are three that we consider particularly important.

  • DrRacket is a program development environment that supports the Racket programming language, which we use in this course. Racket is a variant of Scheme, which is itself a variant of Lisp, one of the first computer languages.
  • Firefox is the preferred Web browser in this course. You should be able to access Firefox through the icon in the task bar that shows a small red animal holding a sphere.
  • The terminal window supports textual interaction with the operating system. At times, the terminal window provides the most convenient way to interact. You should be able to access the terminal window through the picture of the screen in the task bar.

Making the Most of the GNU/Linux Environment

This is a class in computer science, not in using GNU/Linux. Hence, we will provide you with only the basic instructions for using GNU/Linux. It is, of course, possible to use the GNU/Linux system in more advanced ways. You may find it useful to talk to other folks who use the systems to learn particular tricks that they find valuable. We will also point out a few from time to time.

Here’s one: Xfce supports multiple desktops. You can see a two-by-two grid of desktops in your task bar, with small representations of each window. You can switch desktops by clicking on any of the four. You can also drag windows between desktops. Many people find it helpful to use separate desktops for separate tasks, such as one desktop for documentation and information and another desktop for programming. It’s also useful to keep one desktop clear, so you can use it for looking at files. The corresponding lab will give you some opportunities to explore desktops.

Self Checks

Self Check 1: Terminology

Make a list of three important terms we used in this document and their meanings.

Self Check 2: Free and Freedom

What are the two meanings of “Free” associated with GNU/Linux? Why is each important.