Shrink-to-fit tools

9th June 1995 at 01:00
One frequent limiting factor of computers is that the programs you want to store on your floppy or hard disc simply will not fit because there is no space left.

To the rescue come compression programs which use mathematical formulae to store files in a more compact form. It is claimed that the average file compresses by 50 per cent, but it depends on the file types you deal with. An A4 letter written in ClarisWorks will compress from 5K of disc space to 3K, a saving of 40 per cent; a screen picture that originally took up 60K can reduce to 26K, a saving of 57 per cent. On a hard disc capable of storing 40 megabytes of information, I managed to store about 60 megabytes.

Compression programs can handle documents and programs automatically and transparently, compressing them on your hard disc when you are not using them and expanding them automatically when you are. You will notice a slight slowing when you have set up your computer in this way, but balance this against your gain in space.

Compression programs are a boon when you want to decrease a file simply to fit on a floppy disc or to send a smaller file over a network or by e-mail via a modem. But when you have compressed these files, will the person to whom you send them be able to expand them?

Most compression programs have an option to create a "self-expanding archive", which means that the file is compressed and has a little program in with it that will allow the recipient simply to click on the file to expand it (on the Internet the network of international computer networks you often see the extension ".sea" for these self-expanding files).

Commercial compression programs exist for most of the computers found in schools. The facilities they offer are many and varied. My favourite Norton Disk Doubler Pro for the Macintosh offers all the facilities mentioned above and copies files more quickly, archives files, splits them if they are too large for a floppy, offers five compression techniques and much more.

There are also sharewarepublic domain compression programs such as Stuffit (MacPC) and ArcFS and SparcFS (Acorn) that can be obtained from user groups, magazines, Internet etc. These are cheaper than commercial programs, but if you use them often, consider the security, support and documentation if things go wrong.

There are horror stories of people who compress files using one program and then try to compress them again using another, or of people trying to compress the compression program itself. However, when used sensibly they offer a great deal of flexibility, can save you buying a new hard disc and save money on floppies and e-mail.

For Macintosh. Norton Disk Doubler Pro, Pounds 79, Amtech, tel: 01202 476977. Stacker, Pounds 63, Stac Electronics, tel: 01344 302900.For Acorn. Squash comes with later versions of RiscOS. CFS (Compression Filing System) Pounds 34, Computer Concepts, tel: 01727 840303.For PC: Doublespace is already included free in MS-Dos 6 and later versions; Stacker, Pounds 63, Stac Electronics, tel: 01344 302900

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