To use any of the computers in the Mathematics Local-Area Network, one must log in, identifying oneself by giving a user name and a password. You will have received a MathLAN user name and password from the instructor if you did not already have one. If you have not received a MathLAN user name and password, or if you have forgotten either one, please tell the instructor.
When it is not in use, a MathLAN workstation displays a login screen with spaces into which one can type one's user name and password. (If the workstation's monitor is dark, press the <Shift> key or move the mouse and the login screen will appear.) Typically, the space labelled Login: is outlined in red; this means that it is ready to receive a user name. Type in your user name, in lower-case letters, and press the <Enter> key. Now the space labelled Password: is outlined in red. Type in your password and press <Enter>. (Because no one else should see your password, it is not displayed on screen as you type it in.)
At this point, a computer program that is running on the workstation consults a table of valid user names and passwords. If it does not find the particular combination that you have supplied, it pops up a message box saying that the attempt to log in was unsuccessful and inviting you to try again. Press the <Enter> key to dismiss the message and re-enter your user name and password. Consult the instructor or the system administrator if your attempts to log in are still unsuccessful.
When the login program has validated your user name and password, it runs the HP VUE user interface, a program through which one manages various programs and resources that the workstation can access. It takes a few seconds to prepare this interface; during this short period of preparation, the workstation displays a blue transition screen.
When HP VUE takes over, you see at the bottom of the screen a front panel decorated with a variety of icons. You can use most of these icons to activate computer programs. Moving the mouse around on its pad causes a mouse-controlled pointer to move around in a corresponding way on the screen. If one places this pointer on top of one of the icons and clicks on the leftmost of the three buttons on the mouse (pressing and releasing it), the program represented by the icon starts to run.
The rest of the screen is occupied by one or more windows, displaying output from a computer program. When one logs in for the first time, one such window contains a greeting and some basic advice about the user interface. If you want to set this window aside for the moment, with the possibility of returning to it later, look closely at the upper right-hand corner of the window, where the frame contains a small square with a dot in it; if you move the pointer into that square and click on the left mouse button, you minimize the window, closing it up into a small square at the left-hand edge of the screen. (A minimized window can be restored by moving the pointer onto it and clicking the left mouse button twice in rapid succession.)
When one is done using a workstation, one must log out in order to allow other people to use it. To log out, move the pointer onto the EXIT icon near the lower right corner of the front panel and click the left mouse button. A confirmation box will pop up, asking you to verify that you're ready to log out; move the pointer onto the word OK near the bottom of this box and click the left mouse button. HP VUE vanishes, and after a few seconds the login screen reappears; this confirms that you're really logged out.
The Scheme system that we shall use in this course is not represented by any icon on the front panel. To run it, one must invoke it by name. The computer program that reads and responds to such invocations is called the shell, and one's interactions with the shell take place in a window generated by a program called a terminal emulator. The particular terminal emulator that we shall use is named hpterm.
To start up hpterm, move the pointer onto the small monitor-and-keyboard icon, fourth from the left on the bottom row of the front panel, and click with the left mouse button. Shortly a window will appear, displaying the shell prompt -- the name of the workstation on which the shell is running, followed by a percentage sign. This prompt indicates that the shell is ready to receive instructions.
One types in such instructions using the keyboard. Text from the keyboard is directed to whichever window on the screen is ``active''; usually this is the window in which the pointer is located. Move the mouse pointer into the hpterm window to make it active. Notice that the active window is outlined in coral rather than aquamarine.
To shut down hpterm, press <Ctrl/D> -- that is, hold down either of the keys marked <Ctrl>, just below the <Shift> keys, and simultaneously press the <D> key. (On our workstations' keyboards, the keys marked <Ctrl> (``control'') and <Alt> (``alt'' or ``meta'') are somewhat like <Shift> keys, in the sense that they modify the effect of other keys that are pressed simultaneously.) The shell program interprets <Ctrl/D> as a signal that you have no more instructions for it and halts, and the hpterm terminal emulator closes the window automatically once the shell stops running.
It is a good idea to change the password associated with your account shortly after you receive it and every few months thereafter. The program that one uses to change one's password is also invoked by its name, password.
Choose a new password. Make it something that you can easily remember, but not an English word or a name, since it is easy for system crackers to break in by guessing your password if you choose it from one of those categories.
Open an hpterm window, move the pointer into it, and type the word password. The password program will prompt you once for your old password -- the one you logged in with -- and twice for your new password. If you give your old password correctly and the two copies of your new password match, the program will substitute the new password for the old one in the table that the login program consults. The old password will be discarded and will not be recognized in subsequent logins. (If the attempt to change the password fails for any reason, however, the old password will be retained.)
After running the password program, the shell takes over again and issues another prompt. You can invoke as many programs as you like from the shell, one after another, before pressing <Ctrl/D> to leave the shell.
To run the Scheme system, move the pointer into the hpterm window, type the word scheme (all in lower-case letters), and press the <Enter> key. Scheme will print out a header and then issue its own prompt (a greater-than sign), indicating that it is ready to examine and process any Scheme program that you submit to it:
Chez Scheme Version 5.0c Copyright (c) 1994 Cadence Research Systems >
To shut down Scheme, press <Ctrl/D> at the Scheme prompt. The shell takes over and generates another prompt once Scheme has stopped.
Many of the handouts and other materials for this course will be distributed over the World Wide Web rather than in paper copies. One can display World Wide Web documents in a window on a MathLAN workstation by invoking the Netscape Navigator program. To run Netscape Navigator, move the pointer onto the ``walking N'' icon near the middle of the bottom row of the front panel and click the left mouse button.
The first time you run Netscape Navigator on MathLAN, two message boxes pop up. One of them asks you to consent to the terms of Netscape Communications Corporation's licensing agreement; the other requests permission to create some configuration files in your home directory. It's all right to approve both of these requests by clicking on the appropriate word. The pop-up boxes then disappear; you won't see them on subsequent uses of Netscape Navigator.
Initially, Netscape Navigator displays a World Wide Web document containing its logo, version number, copyright notice, and such like. After a minute or so, or sooner if you click inside its window, the program replaces this document with a startup page. By default, this is the front-door page of the Netscape Communications Corporation, but you can arrange to have any document serve as your Netscape Navigator startup page on MathLAN.
To shut down Netscape Navigator, move the mouse pointer on top of the word File in the upper left-hand corner of the window, on the menu bar. Press and hold down the left mouse button. A list of operations appears, and the Exit operation is at the bottom of this list. Still holding down the left mouse button, move the mouse pointer on top of the word Exit, then release the mouse button.
Netscape Navigator can display any document on the World Wide Web. One way to refer to such a document is to give its Uniform Resource Locator, or URL, which is a kind of address by which Netscape Navigator can locate and request the document. For example, the URL for this document is
http://www.math.grin.edu/courses/Scheme/getting-started.html
To direct Netscape Navigator to load a document for which you know the URL, bring up the File menu again and select the Open Location... operation. A dialogue box pops up; move the mouse pointer into the long rectangle in the center of this box, click with the left mouse button, type the URL into the rectangle, and press the <Enter> key at the end. The dialogue box disappears and Netscape Navigator loads the requested document.
Because URLs are notoriously hard to remember and to type accurately, Netscape Navigator allows you to place a bookmark on any interesting or important document that you reach. To place a bookmark on the document currently displayed, move the mouse pointer onto the word Bookmarks on the menu bar, press and hold the left mouse button to bring up the corresponding menu, and select the Add Bookmark operation. You can subsequently return to that document by bringing up the Bookmark menu again and selecting from it the title of the document.
Each MathLAN user can configure Netscape Navigator to reflect his or her own preferences. Between logins, these preferences are stored in a file in the user's home directory; when Netscape Navigator is started during a later session, they are reinstated from that file.
Every user of Netscape Navigator on MathLAN should at some point perform two specific configuration steps:
To make this your startup page, bring up the Options menu from the menu bar and select the General Preferences operation. A pop-up window appears, allowing you to configure many features of the general appearance of Netscape Navigator. The rectangle labelled Home Page Location contains the URL of the document that Netscape Navigator displays by default after its copyright page. Replace the contents of this rectangle with one of the URLs shown above. (This does not have to be a permanent change; you can change your mind about this configuration at any time within Netscape Navigator.) To erase the current contents of the Home Page Location box, move the mouse pointer to the left of the first character in the box, press the left mouse button and hold it down, and drag the mouse pointer rightwards until the entire URL is displayed in reverse video, white letters on a black background. Then release the left mouse button and type the new URL; the old one will vanish as soon as you start typing. Once you have entered the new URL, move the mouse pointer onto the button marked OK at the bottom of the pop-up window and click on it with the left mouse button.
To reduce the size of the disk cache, bring up the Options menu again and select the Network Preferences operation. Again a pop-up window appears. Erase the number (typically 5000) that appears in the rectangle labelled Disk Cache and replace it with 0. Finally, click on the OK button at the bottom of the pop-up window.
This document is available on the World Wide Web as
http://www.math.grin.edu/courses/Scheme/getting-started.html