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See also the home page for Contents and a search facility for this site.
www.technology1.co.uk
Computer Software - Good software available at low cost.
Linux - Introduction to Linux. What it is and how to install it.
Home Computers - some historic home computers and how to emulate them on a modern PC.
There is often a choice about which format to use when saving a file. It is desirable to keep files as portable as possible, that is capable of being read by as many applications as possible. Ideally files should be portable not only from one application to another, but to different operating systems and computer types. This makes it possible to use data without being tied to any one computer type or application. Another big advantage in using well established universal file formats is that they are more enduring. Experience has proved that computer software continues to support older, well established file formats, and so we can be assured that data in these forms will continue to be available to us.
The Internet and web are cross-platform technologies. They do not depend
on the use of any one particular operating system or computer type. Some software
companies would like to lock people into their products including their operating
systems and guess who is the BIGGEST offender in this respect!
A good principle is to use the simplest format possible which will retain all the required information, and indeed may sometimes be worth suffering some small loss of information in order to use a more simple format.
Text is inherently the most portable format, but I have known cases where even simple text is supplied or requested in the native format of some particular WORD processor! This may be the case when teachers supply documents in the form of computer files for students, and where employment agencies request a C.V. in a particular format.
Graphics are capable of being stored in formats suitable for all major platforms and this is nearly always the case when images appear on the web.
In computer terms, portability is the ability to transfer data etc from one computer environment to another while preserving the ability to use it One of the first obstacles which had to be overcome was the physcal ability for data to be passed from one computer to another, i.e. the hardware side of it. In early computers even this was not possible, especially when casettes were used to store software. Even when the 5+1/4 inch floppy disk was introduced, different computers had, in general, different formats. When the 3+1/2 inch floppy was introduced there were ways of taking care over the disk format so that computers could read disks written by different types. The Macintosh, the Atari ST, and the later versions of the PC, notably the IBM PS/2 could transfer data using 3+1/2 inch floppies. The industry standard RS232 which had been around before personal computers was also a universal method of transferring data between different computer types.
There are three main types of personal computer operating systems in current use.
The first two of these are used on the industry standard PC based on Intel processors and their equivalents. For practical purposes computers using the Linux operating system might as well be a completely different computer type. Then there are various versions of each, including the use of earlier versions of the the operating systems.
There are different levels of portability.
The Internet has done a lot to promote portable file types. What determines portability and the reason they work is the fact that browsers have been designed to deal with a number of file types. This is particularly applicable to graphics files. It doesn't just happen by accident. Underlying this is the way that modern computers have some essential features in common like the ability to present graphics in windows on the screen.
Text files are difficult to define precisely. They essentially consist of the normal printable characters of the ASCII character set. These are letters, numbers, the 'space' character, and characters such as $, &, @ etc. The codes range from 'space' (code 32) up to code 126. They may also contain 'carriage return' (code 13) and 'line feed' (code 10) and possibly 'tab' (code 9), and the end of file character, code 26.
The codes are defined by the ASCII code, American Standard Code for Information Interchange. This pre-dates modern computers and was used for such things as teletypes which were really a pair of electric typewriters on which you could press keys on one machine to type on the other some distance away.
Depending on the context, a text file is usually intended to be viewed or printed simply as the text it contains. It will normally have extension .txt.
Some other file types are in made up entirely of these characters and can be regarded technically as text files. For example Rich Text Files, and HTML files. On examination these can be seen to consist entirely of ASCII text. This can be seen if the file is opened in a text editor such as Notepad. However, such files are intended to be presented differently from their simple text content. They are not normally considered to be text files, but this will depend on the context.
For example such files could be read from a computer program which can only read text files.
The great thing about text files is that they are very portable. They do not rely on any particular software to read and display them, and are even readable by entirely different computer types.
The ASCII character set is now almost entirely universal across all computers. It was not always so. As recently as the early 80's not all computers used it!
Text files may or may not specify where the new lines are intended to occur. This gives rise to some confusion.
The proper way of specifying a new line in a text file is to use the carriage return character (CR) followed by the line feed character (LF). This represents the action of a teletype. CR simply moves the print position back to the beginning of the same line. LF moves the paper up by one line. On a teletype, if CR was used alone, the next line would overprint the previous one. If LF was used alone it would move to the next line without returning to the beginning of the line.
Modern software does not always stick to this formula. Often a text editor, when it reads a file, will interpret either CR or LF, or both, to implement a single new line. This is OK. Problems come when a file is written to disk without using the correct format.
The type of text file which defines all the new lines is intended to be displayed or printed with the new lines exactly where they are specified. Such files were used in early personal computers. The current practice is to omit most of the CR and LF codes from a text file and allow the software or printer to decide where to put the new lines. This arises primarily from the use of more sophisticated software and printers which decide where the new lines are required to go, depending on such things as font and type size.
RTF files, (Rich Text Format) were invented by Microsoft to allow different word processors to use a common file format. They allow text sizes and fonts to be specified, and also certain other formatting features such as bulleted lists and tables. This is a really good format. It is good practice to use RTF files if you wish to specify fonts etc, but do not need some more advanced features of a particular word processor, such as graphics. RTF files are usually much more compact than the word processors own native format. They are well suited for sending documents as email attachments.
Upon closer examination an RTF file can be seen to consist entirely of ASCII text. Some of this is used to specify the format required and is not part of the document text.
E.g.
\par
\par A line in an RTF file.
\par
HTML files have some things in common with RTF files. They too are constructed entirely of ASCII text and are intended for portability between different software. In common with all Internet files they are also intended to be independent of the computer type or the way it is set up (e.g. the fonts installed).
The Internet is required to work on a range of different computer types and operating systems. Files used on the Internet should be capable of being used on these different systems, and hence must not be specific to any one computer or operating system, (in particular the PC with Windows!).
Compression is a method of making a file smaller than it would otherwise be.
There are two kinds of compression, 'lossy' and 'non-lossy'. With lossy compression some data is thrown away in order to facilitate the compression. It is not possible to retrieve the original file exactly as it was. There is usually some sort of degradation of quality though this may be barely perceptible. Examples of lossy compression are JPG for photographs and MP3 for sound.
Non-lossy compression achieves a reduction in file size without any loss of data, i.e. the original file can be retrieved exactly as it was before compression. At first sight it seems impossible. The degree of success depends greatly on the nature of the data in the file. No significant compression can be accomplished if the file consists of all possible byte values in an apparrently random order, and indeed this is almost certainly the case if a file has already been compressed, thus there is little point in trying to compress a JPG file. Conversely the most successful compression will occur if the data has a large bias towards the occurrence of a single character, especially if these appear in consecutive sequences. The most common example of non-lossy compression is the ubiquitous ZIP file type.
The main file types for graphics are BMP, JPG and GIF. Each has advantages and disadvantages and the best choice depends on the requirements.
This is a no-compromise graphics format which precisely defines the colour of each pixel of the image. Variations of BMP files exist which use different numbers of bits of precision for the pixel colours. It is sometimes called "Windows Bitmap" and there is some doubt about how much software of non-windows systems can display files in this format. This format is suitable for storing the master copy of graphics where quality is all-important, and where there is no concern about the disk space the file will occupy. Also suitable for submitting graphics files for printing, provided the print company can read it.
This is primarily for photographs, indeed JPG stands for Joint Photographic Experts Group. It is a format with lossy compression designed to preserve the visual appearance of the image as well as possible. The degree of compression can be varied greatly when the file is written. The degradation of the image is most evident when there are sharp transitions of colours of high contrast. Notably when text is superimposed on a picture.
These two pictures are JPG files with different amounts of compression applied. The second has much greater compression and is clearly degraded, but is nevertheless a much smaller file.
Graphic Interchange Format. This format limits the number of colours in the picture and by doing so reduces the file size in some cases. If the number of colours is already sufficiently low there will be no change to the image. It is therefore particularly suitable for images with uniform areas of single colour such as those produced by computer drawing and painting packages, and cartoons etc. It is also suitable for black and white line art, and notably for sheet music.
GIF files can also have transparent areas. Animation is also possible.
The following cartoon is ideal for presenting as a GIF file. This example also has a transparent background. For comparison the image is also shown here in a JPG format with approximately the same file size. JPG is clearly unsuitable in this case.
See the Sound Technology part of this site.
There is an excellent web site giving a huge amount of information on file formats:
Cheap or free software available on the Internet and elsewhere.
Microsoft
Internet Explorer is the brower supplied in the Windows operating system but
there are others which people might prefer for various reasons.
Firefox is the main rival to Microsoft. It is the successor to Netscape which
was the original browser and which played a large part in the development of
the Web. Firefox is available free on magazine disks or as a download from:
www.mozilla.org
A good quality anti-spyware program which is fully functional and free. It particularly deals with the sort of threats which come from the Internet, and might be all you need.
It is frequently available free on magazine disks, or is available for download
from:
www.spybot.info
A good general anti-virus program available at low cost or in a free edition called AVG Free.
From Softwin. Normally requires a fee but might sometimes be available on
PC magazine disks. A trial version can be downloaded.
www.bitdefender.com
Paragon Hard Disk Manager is often available on PC magazine disks, or can be purchased at low cost. The program can save a whole drive as an image which is especially suitable for backing up the partition with the operating system. It is difficult to do that any other way. The great thing is that you can create a self-conained bootable CD which will run without any operating system installed. It is based on Linux and contains its own operating system. This is an excellent way of recovering from a PC disaster resulting in a non-functioning operating system.
Paragon HDM can also re-partition a drive, but take care. I have had some problems with this.
Paragon are based in Germany but the product is available in good English.
This is software which allows you to create your own fonts, either from scratch, or by editing an existing font (providing copyright permits it). Such software is a bit specialised and because there are so many fonts already available. As such it is relatively rare and hard to find. It might appeal to:
There is at least one prestigious font creation package, Fontographer, from Macromedia, but it is expensive. The following is a much lower cost alternative:
Font Creator Program, FCP
From High-Logic Software. A time-limited trial version is available from their web site:
There is a great program called The Font Thing by Sue Fisher in Australia. It is a nice compact application which primarily allows fonts to be viewed, including both the fonts installed in the system and fonts not installed, e.g. files on a C.D. This latter feature is particularly useful. The program seems to be very fast and efficient. It also allows you to group fonts together into collections of your choice for the purpose of classifying them, and does so without having to move the actual files. The program seems to be entirely free of charge and does not even ask for a donation.
It can be downloaded from Sue Fisher's site which also has many font-related links.
Sue Fisher's Site: www.ozemail.com.au/~scef
OCR is Optical Character Recognition which converts a graphics file, (for example obtainable from a scanned paper document), to an editable text file.
Transym OCR, (TOCR)
To quote the authors: "It is a no frills product with the accent being entirely on accuracy". I found it works well with a reasonably good original document. There may be need to edit the resulting text to correct some errors, but the process is much easier than typing in the document. It seems to be supplied entirely free with no strings attached, and even includes some of the source code in Visual Basic. Good!
OCR is Optical Character Recognition which normally applies to reading of text from a graphics file, and converting it to an editable text file. Music OCR is a version which works with sheet music. The ideal form of output is a MIDI file which would then allow the music to be played, and with appropriate software, allow it to be edited, transposed to different keys, played at different tempos and in different instrument voices, and printed.
For some time I have thought a sheet music version of OCR would be desirable, but didn't know of the existence of anything. It is quite a specialist thing. Even ordinary OCR has only recently become affordable. Now there is music OCR.
For more about this see Music and Sound related software below.
This has been available in the past free on a PC magazine disk, including Lotus Word Pro, a highly specified word processor, Lotus 123 spreadsheet, once the leading spreadsheet application, and Lotus Approach database application.
Sometimes Lotus Word Pro has been available on its own.
This was once made available on a magazine CD. Borland Visual dBase has an excellent pedigree having evolved from DBase III which was once the leading database application for the PC. DBase III was bought by Borland who are a leading provider of programming software using C and Pascal languages.
See the Sound Technology part of this site.
The main Contents page: www.technology1.co.uk
This site is written by S. J. Farthing, Portsmouth, England.
My personal site and e-mail address are at: www.farthing.me.uk