In last week's Boot Camp we looked at some of the ways files can be transferred from one PC to another. In part two we're focusing on the types of files you're most likely to send or receive, and how to squeeze a digital quart into a pint pot.

Files are identified by a three (sometimes four) letter or number code -- called an  'extension' -- that comes after the full-stop following the file name. There are literally hundreds of different types but don't worry, most of them you'll never see or have to worry about as they are only used by Windows and the programs on your computer. Unless you're a heavy-duty PC user, or running exotic applications you will probably only ever encounter a dozen or so different file types. However, if you do comes across something unusual on your machine and you want to find out what it is, or what the extension means there's a handy utility in Windows Explorer and My Computer. It's on the View Menu, under Folder Options, click on the File Types tab and you'll find details of all the file formats your machine is currently using.

Since word processing is the single most popular application for most PCs the files you're most likely to want to transfer to another machine will contain text. There are two distinct types of text file, for documents and plain text. Document files are created by your word processor, they contain generic formatting information, such as character attributes  -- typeface and size, bold and italic letters etc., and layout styles. MS Word and WordPerfect document files have the extension .doc, Lotus WordPro uses .lwp, Word for the Mac uses .mcw, and so on. In general these documents are meant to be read by the word processor program they're written on, though most WPs can also read documents in an alien file format but some style information may be lost. However, the big problem with generic WP file formats is that they take up a lot of space.

If you want to transfer a large amount of text from one PC to another, on disc, via a network or over the Internet (as e-mail) it is more convenient, and usually a lot quicker, to send it as a plain text ASCII file (see Jargon Filter). Text files have a .txt extension and contain just the words plus simple style and layout information. Plain text files can be read on any word processor but most importantly, they are quite small. For example, a 1000 word Word 97 document requires at least 32 kilobytes of disc space; the same 1000 words occupies only 8kb or so as plain text. That makes a big difference to the time it takes to send a document by e-mail, or the number of documents a floppy disc will hold. There's also the possibility that the recipient of a formatted WP document may not have the same program on their computer and will be unable to read it. By the way, most newspaper, magazine and book editors prefer to receive submitted copy as plain text (whether on disc or by e-mail) as it can be easily imported into page layout and DTP programs where it will be adapted to their house style.

Next, pictures and graphics files. They make up one of the largest families of file formats but again there is a degree of common currency that allows images to be easily swapped between computers. The standard Windows picture file format is the bitmap, with the extension .bmp. Bitmap files can be very large indeed; a small colour picture can easily swallow up several megabytes of disc space. Bitmaps are often too large to get on a floppy disc, and sending a bitmap file over the Internet takes forever. The alternative is to compress the data, by discarding unnecessary information and picture details the eye cannot see. The most widely used compression scheme is JPEG (extension .jpg), which can reduce file sizes by factors of 10 to 100 times without significant loss of quality, moreover JPEG files can be displayed on a very wide range of paint box and graphics programs. Pictures on Internet web pages are usually JPEG files; simple graphics (buttons, icons, logos, backgrounds etc) are normally sent as compressed GIF files (Graphics Interchange Format), with the file extension .gif.

When it comes to moving very large or complicated lumps of software around between computers a more precise means of reducing file size is needed. Data can be reliably compressed using a variety of techniques; the best known is 'Zipping'.  Files with the extension .zip are widely used for downloading information and programs from the Internet. Some compressed files are self-extracting. Once the file is on the PC hard disc (and checked for viruses) double-clicking the file icon automatically opens and installs the file or program. However most compressed files rely on the PC having its own extraction utility program, such as WinZip or PKZip. Clicking on a zipped file automatically starts the extraction program. Shareware versions are freely available as from the web sites we’ve listed. No Internet PC should be without one of them! These programs also allow you to create your own compressed files, packing very large amounts of text or data onto floppy discs, or for sending over the Internet.

You might also come across a coding scheme called Uudeview, which creates files with the extension .uue. This file format is used to convert information -- pictures, programs etc. -- into plain text characters, so they can be sent over the Internet as e-mail. Uudeview coded files look like huge documents full of gobbledegook text. They can be easily decoded using a simple Windows program, also available in shareware form from the web site on the Contacts list.

Next week, working with pictures







American Standard Code for Information Interchange, text coding system, recognised by all PCs


Desktop publishing -- makeup and layout programs used to design pages in printed documents, magazines, newspapers and books


Joint Photographic Experts Group -- part of International Standards Organisations, responsible for devising software compression systems. Picture file format used for storing photographs, data is compressed thus saving space and reducing download times on Internet pages



If you need to quickly make a copy of a floppy disk -- maybe a colleague needs to see some files you've been working on -- then Windows 95 and 98 can help. From your desktop or the Start Button open My Computer then right-click on the floppy disc icon and select Copy Disk on the menu. Windows then reads the entire contents of the disc into the PCs memory; a bargraph shows how the copy process is progressing. When the indicator reaches halfway Copy Disc will ask you to remove the original disc and load a blank formatted floppy. Make there's nothing on it or it may be overwritten, click OK and the information is read back to the second disc.

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