Computers: Maintaining operations in an emergency: An operating system is a basic requirement, but the latest versions offer much more than is needed and can create problems - Nigel Willmott offers some tips on how to prepare for the worst

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The Independent Online
EVERY COMPUTER needs an operating system to control such things as the transfer of data from processor to keyboard, screen and disks and to organise the storage of information in files and directories. But the latest versions offer much more.

The main operating system for PC-compatible systems is Microsoft's MS-Dos, though there is an alternative in Digital Research's DR-Dos, which sometimes offers new features ahead its rival. The core programs controlling basic operations stay pretty much the same from version to version. What have been added are programs which carry out 'maintenance' and file management procedures that used to be provided only by separate 'utility' programs like Norton Utilities or PC Tools.

In version 6 of both MS-Dos and DR-Dos the main additions are file compression and disk defragmentation programs.

Disk compression 'squeezes' files by taking out redundant bits like space characters, so text files which include a lot of spaces can be stored in about half the normal disk storage. The MS-Dos Doublespace and DR-Dos Superstor programs compress files on storing them and expand them when they are 'retrieved' - loaded back into the system. Both do basically the same thing, although, for what its worth, Doublespace seems the more user-friendly.

Defragment programs do a sort of electronic tidy-up. As disks become fuller, parts of the same file may be physically stored in different sectors of the disk and the information brought back together when retrieved by using an index that cross-references all the different bits. But this slows up the time it takes to load a file. Defragment programs re-store all the data on disk so that all the information that relates to one file is stored in the same physical location.

There have been problems with compressed disks, but there also now many millions of users who have survived without problems - and plenty of users without compressed disks have had problems with losing data in disk crashes.

Two tips are to 'back up' - to copy - data regularly and to keep an 'emergency disk' handy. It would take about 60 floppy disks and a large amount of time to back-up a complete 80-megabyte hard disk, so a more practical way is to keep all data files in one directory on the hard disk and just copy that - programs can be reloaded from the original floppy disks.

If the hard disk crashes you may not be able to load the operating system from it and will therefore be prevented from doing anything. So it is a good idea to keep a slimmed-down version of the operating system on an emergency floppy disk because the computer always tries first of all to load from the floppy disk drive. It is also worth keeping on the emergency disk some utilities like Norton's Disk Doctor which can recover data from disks where the file structure has been corrupted.


MS-Dos 6.2: Microsoft; pounds 46.

DR-Dos 6: Digital Research; pounds 49.

Norton Utilities 7: Symantec; pounds 105.

PC Tools: Central Point; pounds 65

Best advertised prices inc VAT.

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