| Table of Contents |
Chapter 7 Output devices historical and today
(Chapter 7 part 1)Chapter 7 is about output devices as peripherals
Peripherals are computer devices that are attached to the computer rather than being inside the computer. Some of these devices are sometimes incorporated into the main desktop or laptop, but for the most part are external. For ease of hardware maintenance, the monitors and printers are best located outside the box containing the mother board and the CPU.
Gotcha!
Several manufacturers tend to package as many components as possible together, in particular the monitor and the mother board/cpu, in one case. This practice tends to lock-in the owners and force them to send the entire unit in for repair when the monitor or the main box goes bad. This is frequently a great inconvenience and for the careful buyer, unnecessary. Monitors tend to be standardized and interchangeable. Often a local repair center will be able to provide a loaner monitor while doing repairs on one that is not working properly. Unfortunately, by not using industry standard parts, manufacturers can force an owner to purchase parts and/or repairs from their factory or their proprietary repair centers. This is usually at considerably higher prices than those of local repair shops that can use industry standard parts and the factory repair centers are generally not local requiring delays and added expense for shipping
Industry Standard Parts
Many computer manufacturers and all of the computer build-it-yourself kit manufacturers use industry standard parts. In general, industry standard parts are of high quality, much less expensive and are frequently sold at substantial discounts. Industry standard parts are usually readily available at local electronics stores and mail-order houses advertising in the computer magazines found at newsstands. This all should be considered before making a computer purchase.
Output devices complete the Computer Equation:
Input + Processing ='s Output
There are many different types of output devices. As with the input devices, there are many ways that a computer must give users output.
The Monitor, a necessary device
The most common output device is a monitor or cathode ray tube (CRT). It is also called the Video Display Tube. Some video displays only have one color of characters; they are called monochrome (one color). Monochrome monitors are inexpensive and an early technology. They are seldom used anymore. Most color monitors are video graphics array or super video graphics array (VGA or SVGA). These are the best monitors and can display as many as 16 million colors at a very high resolution.
What is monitor resolution?
Resolution means how many tiny dots there are on a video display. This means how many in a row across and how many in a column deep. In monitors the dots are called pixels. A standard VGA monitor is 640 pixels across by 480 pixels deep. There are many resolution options. Common sizes are 640 x 480, 800 x 600, and 1024 x 768. Each of these may have color selections from 16 colors to 16 million. The most common colors selection is 256 colors. This may change as manufacturers continue making improvements.
Video memory and speed
An additional factor in the monitor specifiations is the monitor drivers memory size. This is independent of the regular memory (RAM) and is usually 1 or 2 megabytes. The standard is 1 megabyte , but 2 megabytes are necessary for very high resolution and 16 million colors. With monitors speed is everything. A monitor must place its images on the screen many times per second. This is called the refresh rate. The higher the refresh rate the less eye strain. There are accessory video boards available, that accelerate this rate. A very high rate is necessary to accomdate MPEG this current industry standard for computer animation. The latest computers with Pentium® processors and MMX tm technology are designed to accomodate animation and sound( multi-media). It is only a matter of time before all computer manufacturers in some manner readily accomodate very high resolution animated graphics and sound.
Monitor size is important
Today's ultra-fast computer processors and high speed monitor drivers are capable of producing remarkable monitor screen image quality. In general, equal to or greater than that of television. This has also permitted a dramatic increase in the size of the viewing area. Early monitors were mostly limited to screen sizes of 11 inches. For many years the 13 inch monitor was considered a standard. This quicky moved to 14 inches, then 15 inches and today 17 and 21 inches. Of course, as with television, the larger the screen the greater the cost of the monitor. However, monitor size is important because the larger monitors minimize eye-strain. The bigger the better.
Eye strain is a real problem
It is well accepted that prolonged work at a computer monitor is very hard on the eyes. It seems to bother some much more than others, and many people have severe headaches after only a few hours working on a computer. Others, do not get headaches, but very few can stand working on a computer all day, every day, without special glasses. When purchasing a monitor the buyer should always purchase the largest affordable that the computer system will support. The trend today is to market computers without monitors. This gives the buyer the opportunity to purchase the best possible monitor.
The second most common output device is a printer
Printer resolution
Printers also have resolution, but it is not expressed in pixels. It uses a photo-engravers standard called dots per inch (square inch) or DPI. Early laser printers, printing only black on white, started with 150 DPI resolution. This soon became 300 DPI and for a time this was the industry standard. The latest laser non-color printers are capable of 600 DPI. Some of the high-technology industrial/commercial color printers are capable of this resolution in color, but are really not considered affordable for the non-industrial user. Today's more affordable color ink jet printers print as high as 720 DPI (dots per square inch). This is so close together that they are virtually undetectable to the naked eye. Color laser printers produce good color resolution, some in excess of 600 DPI, but these are expensive and are targeted to the commercial market. There also are many different kinds printers. There are too many to know all about, but there are some that you should know more about and there are things you should know about almost all printers. Printers vary in speed, price, print quality, and special capabilities. These variables (differences) are what you should think about when you buy a printer.
Impact printers (are history)
Impact printers strike or hit a ribbon with the pattern of the letter or character to be formed. Some form of a hammer hits the pattern and the ribbon transfers the image/impression to the paper with carbon dry process ink. Some ribbons are fabric impregnated with ink and other are clear plastic tape with carbon black on it held there with a weak adhesive. Ribbons can be expensive and difficult to obtain. There was little standardization in the printer business and each manufacturer makes their own design for each machine. A catalog for printer ribbons looks like the roster for the NFL, NHL, and NBA combined!
The dot-matrix printer is an impact printer
It has been the most popular printer of all. It is one of the earliest printers and it has remained popular to this day. It is reasonably fast, reasonably quiet, and reasonably inexpensive. The early models formed a character out of three rows of 3 dots, (9 pins total on the print head). The pins are bundled in a block and are in the print head. The newest models have 24 pins in the printhead and produce near-letter-quality print. If you look closely, you can still see the dots.
Dot-matrix fonts and graphics
Dot-matrix printers can change their font (print style) while they are printing. The ability to change while printing allows dot-matrix printers to do reasonably high-resolution graphics. Dot matrix printers with Red/Yello/Blue/Black ribbons make an attempt at color. The results are very poor by today's standards.The future of dot-matrix printers
The manufacture of dot-matrix printers will soon be a thing of the past. They are being replaced by the ink-jet printer and will become special order only and not carried in inventory by computer stores. Their main value will be in producing carbon/multi copy forms. A good dot-matrix printer can print an original and 3 carbon copies.
Special in class assignment number one Click Here
PART ONE ENDS HERE
Return to Part 3 Chapter 6 Advance to Part 2 Chapter 7
Return to Part 3 Chapter 6 Advance to Part 2 Chapter 7 Pentium is a registered trademark and MMX is a trademark of the Intel Corporation
Copyright 1993, 1995, 1997 4-s Sandra's Small Systems Software 4-s