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General Introduction to Computing and Information Services


Computing and information services available in the Chemistry department fall into two broad categories; those that are unrestricted and those that require authentication via a password of some kind. Word processing is an example of the former, whilst "electronic mail" is of the latter kind.

User Registration

All new students are issued with a "user identifier" and a "password" when they first enter the department. Do not let others see the "password", and try to memorise it before sticking the label somewhere safe. The "user identifier" is used with the Silicon Graphics workstations and will be needed for other services such as "e-mail" (electronic mail). Experiments in "encryption keys" are starting in 1995, and you may also be issued with a "PGP" public and private key.

Deciding which Computer to use

Macintosh computers are available for word processing, document preparation, numerical analysis and display and as terminals for connection to remote computers. They are also the primary system to use if you want to print something. Silicon Graphics workstations are used for molecular modelling, database queries and to support electronic mail.

Do I need to buy my own computer?

Computers cost in the region £500-1500, but the real cost is can be twice this amount if you include the software, perhaps a printer, and a budget for enhancements and repairs in the future. If you intend using the system at home, you may also wish to consider buying a modem. No special "student" deals are available for hardware, but there are a number of "university" specials for software. Roger Hunt in the Centre for Computing Services handles these, and you should check what is on offer before purchasing.
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Location of Computers and Printers

For security reasons, these are not given here. However, you will be told which rooms to use for courses during your first year. Many of the computers are "energy saving" which means they may have powered themselves off when you first encounter them. On a Macintosh system, try pressing the "pwer" key, which is located on the extreme top right hand side of the keyboard, to start such a dormant computer.


The Macintosh computer rooms contain a number of HP Deskwriter printers. Because of the difficulty in securing the ink cartridges on this printer, these are normally only provided during scheduled courses. At other times, you have to provide your cartridge along with paper. When empty, the cartridge can be recharged with Parker Quink ink using a 10 ml syringe obtained from stores. When storing the cartridge, replace the small strip of blue plastic across the gold coloured ink nozzles and put it in the original container, otherwise these might dry up and block. To test if a cartridge is still in good condition, power the Deskwriter up whilst pressing the select button, when a test page is printed. If more than 2-3 nozzles are not printing, the quality of the output will not be good. A blocked cartridge can be resuscitated by allowing steam from a kettle to impinge on the surface for a few seconds. Take care to gently dry the cartridge with a soft tissue before inserting it into the printer. The quality of these printers suffices for most purposes.
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The Components of a Computer

All computers have a common number of "hardware" components;
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The Computer Keyboard

Most systems retain the typewriter QWERTY type keyboard layout for input of text characters. This includes a number of special symbols such as CTRL, BREAK, ESC and "function" keys which a conventional typewriter does not have. You will notice that to produce upper case alphabetic characters on the terminal, either the SHIFT key has to be pressed simultaneously with the required character, or the CAP LOCK has to be set. Otherwise, the character will appear as lower case when it is typed (a rather important distinction in certain environments such as UNIX).

The CTRL, • and ALT Keys

The CTRL (Control) key is unique to computers, and is used to give other keys an alternative meaning, just like the SHIFT key. It is NEVER used on its own, and is required because the normal keyboard has insufficient keys to represent the 256 characters in the so-called ASCII set. Macintosh computers have a special key labelled • which modifies commands in a manner similar to the CTRL key. On IBM style PCs, the ALT key is similar.


This key is always located above the SHIFT key and is normally used to "register" a line of text with the computer.The instruction to press the RETURN key is indicated in this document by . On the Indigo workstation keyboard, this key is instead marked but has the same meaning. This legend is an unfortunate choice, since there is another key marked which is part of the "numeric keypad" (see below). Do NOT use this latter key for RETURN functions.

Function Keys.

Many keyboards have "function keys", whose meaning can be defined by the user or by a program, enabling a set of instructions (a macro) to be reduced to a single keystroke. Such keys can also be given alternative meanings if used together with the SHIFT or/and CTRL keys. MS-DOS based programs often make extensive use of function keys. On the Macintosh the F2, F3 and F4 keys are used for so-called Copy/paste operations.

The Delete/Backspace Key.

This key, normally found above the RETURN key, can be used to correct typing errors and it deletes the preceding character to the cursor. On the Indigo workstations, this key is labelled BACKSPACE, and a separate DELETE key to its bottom right has a separate function.

The TAB Key

This is used as a fast way of moving the cursor horizontally in the forward direction only (or on a personal computer to the next "field" as on a spread-sheet etc). How far the cursor moves depends on where the "Tab stops" have been set. On Unix workstations this is to column 7, ready for eg the entry of Fortran statements. On a Macintosh word processor, you have to set the Tab stop yourself for producing columns in tables etc. Note that there may be different kinds of Tab stop, including left, right, centred and decimal point.

The Numeric Keypad.

Keyboards have an approximately square "pad" of keys on the right hand side, the definitions of which can vary widely. Many programs use this keypad for their own purposes. Normally, the 0-9 keys provide a means of entering numeric data rapidly into a graphing or spreadsheet program.
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The Computer Mouse

The so called "mouse" is a high quality "analogue-to-digital" device which is used to orientate a cursor on the screen to individual "pixel" accuracy, and is held with the cable pointing away from you. Most operate mechanically with three rollers sensing the rotation of a small ball. They can easily pick up dirt and become difficult to operate (it is not a good idea to eat biscuits or drink coffee whilst operating a mouse!). If a mouse feels sticky or rough, it probably needs a good clean. Unless you know how to do this do not try as the teflon rollers can be easily damaged.

The position of the cursor is "registered" with the computer by "clicking" on the mouse button(s). Unfortunately, not all mice work in the same way. For example, Macintosh mice have only one button, and clicks can be either "single", "double" or "press, move and release" in style. Most DOS based windows computers have a two button mouse, whilst Unix workstations use three! It is rarely obvious what a button click will achieve, and this simply have to be established by trial and error, asking someone, or in extremis, reading any documentation! In the notes below, if no button is mentioned, assume that the left hand button on a 2 or 3 button mouse is pressed.

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Screen output is commonly described in terms of viewing "windows", and each screen may contain one or more windows, each associated with a separate task or program. In so called terminal or character-mapped mode, the output consists of typically 24 lines of 80 characters (although this may be adjustable). With simple text line-mode display, each new line appears from the bottom and eventually scrolls off the top. Such windows, whilst still common, are on their way out. Pixel (Bit) Mapped Windows are "bit-mapped" screens where individual "pixels" can be addressed and given an attribute of colour, intensity etc. A small screen consists of 640 pixel positions horizontally and 480 vertically, whilst a medium screen is 832 by 624 pixels in size. Each pixel can be defined in terms of 256 colours (8-bit colour) up to 24-bit colour found on high end workstations . All characters, lines, attributes, font styles and screen graphics are produced from such pixels. Several concurrent "Windows" can be open some of which may even be connected via a network (see below) to other computers. Three are three common specifications for how such windows are handled.
  1. MicroSoft Windows-95 or NT 3.5.
  2. MacOS, currently version 7.5.2
  3. X-Windows (version Motif) found on Unix workstations, currently at X11V6.
Macintosh computers support X-Windows via a program called "MacX", and Microsoft Windows format via a program called "soft-windows". Screen-mode displays can also be saved on a Macintosh as a "screen-dump" which can be inserted ("pasted") into other documents. Many of the displays shown in this documentation were prepared in this manner.

Window Management.

Since a number of windows can be "open" on a screen at any time, certain rules for moving between them and managing them have evolved. There is a measure of commonality between the three types of window noted above, but also many differences and it may take some time for a user to become familiar with the concepts and the differences. You should take encouragement from the fact that it is easier to learn about windows from playing with the real thing, rather than trying to follow written documentation as found here!

In this department we use the standard that the "active" window is seen in its entirety, and "inactive" windows may be obscured underneath as seen in the example above (the top window is said to be "raised" with respect to the bottom). The bar on top of an active window is seen "ribbed" (on Mac screens) or blue (on Indigo workstations). To make a window "active", a single mouse click is required (the left hand button on an Indigo). Only when a window is active will anything typed in from the keyboard be associated with that window (the keyboard is said to be "focused" on the window)

Perhaps the most initially confusing aspect of using a "windows" based screen is in such window management, and you are strongly advised to practice these operations before attempting any serious work.
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The Departmental Computer Network System.

Almost all departmental computers are inter-connected via three types of network.
  1. An "Appletalk" network interconnecting the Macintosh systems and printers in Chemistry and Biochemistry, operating at about 230 Kbaud.
  2. A higher speed "Ethernet" network based in part on optical fibres and connected to a College wide "FDDI" ring. All Unix workstations, many Macintosh and MS-DOS computers and several departmental spectrometers and instruments are connected via the Ethernet, which operates at speeds of 10-100 Mbits per second.
  3. A new network based on "ATM" (asynchronous transport mode) is gradually being introduced. The first Mac and PC are expected to be connected during 1995. This enables services such as videoconferencing to be introduced.
If any part of these networks are down, you may not be able to perform the tasks you wish. If you suspect a problem, alert Sue Johnson or Henry Rzepa. These networks are inter-connected via devices known as "gateways" and can reach the outside world. The UK wide network is known as SUPERJANET, which in turn is part of a world-wide system known as INTERNET.

Remote Connection

There are occasions when access to various departmental computing facilities is required from off-campus. To achieve this, you will need a minimum of a remote computer, a modem, and connection software. Some types of notebook computer come as a bundle with all three. The College offers a number of dial-up lines for use with a modem. These lines all go through one number, which then "hunts" for a free line. You are recommended to use a protocol called PPP. Instructions for Mac and PC users are available.
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We are gradually providing documents like this, lecture note materials, lab course instructions etc via a system called the "World-Wide Web". Because documents can be obtained from any global source, this provides a rich treasure trove of information. "How to"s on how to activate this system are posted in the main computer rooms. You should learn how to operate a Web browser as one of the first things that you do.
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Copyright (c) H. S. Rzepa and ICSTM Chemistry Department, 1994, 1995.