softalk-pc-1982-12-reduced

SYSTEM NOTEBOOKby·AJan BoydIOver the past six months we've seen in detail how to work withalmost all of the DOS commands in versions 1.0 and 1.1 of theoperating system. This month we'll take a close look at one of theremaining commands-mode.This is one of the more obscure commands in the system. Noteveryone needs to understand or even acknowledge the existence ofthis command, but as you become more proficient at using your pc,you'll undoubtedly run into a situation where you'll findmode handy-particularly when it comes time to expand your pcbeyond its present capabilities.Mode exists in two different flavors, depending on which versionof DOS you have. Many users of DOS 1.0 reported problemswith mode, so version 1.1 of the operating system sported a new,enhanced mode command, one that offered many new and desirablefeatures and included everything that had been available on theearlier version. We'll restrict this discussion to mode as it exists inDOS 1.1.Mode , an external DOS command residing on the master disk, isdesigned specifically for use in configuring peripheral equipment. Itactually has several rather distinct uses, and we'll get into each ofthem momentarily; but first we should digress long enough todefine and discuss the concept of peripheral equipment.The term peripheral is a general one denoting any external equipmentthat can be attached to the pc. Generally such equipment interfacesthrough one of the card slots inside the computer. Any of thedevices attached to the pc through a slot can be thought of as a peripheral.This, of course, includes memory cards, video interfacecards, disk controllers, and the like-although these devices are sointegral to the system that they're seldom referred to as peripherals.The Outside Inside. The most general of all peripherals is theprinter; other examples include modems, graphics digitizers (alsocalled bit pads), analog controllers, speech synthesizers, mechanicalarms, music synthesizers, pen plotters, and joysticks. Usually, theuse of the computer for any so-called real-world application requiresthe addition of one or more of these peripherals.Many people quickly discover that the pc can be molded into avery effective word processor simply by the addition of wordprocessing software and a printer. In fact, many of the popular''dedicated" word processing machines are actually microcomputers,and internally some of them closely resemble the pc. All ofwhich really means that the term word processor has become more ofa way of describing the position in the market taken by the manufacturerrather than the capabilities of the machine.Many " word processor" manufacturers are now offering20computational abilities in software as an adjunct to the wordprocessing software that their machines were originally shippedwith; this is not the result of any technological breakthrough, butrather a reaction to today's increasingly sophisticated consumermarket. Similarly, many manufacturers of personal computers arenow offering word processing software packages along with theirpersonal computers. Both the preceding statements apply to IBM,among other companies. You can now do general-purpose computingon their dedicated word processing. machines, and, of course,you can use your pc as a powerful word processing machine.In order for a word processor to be effective, a printer must beadded to the basic computer system. There are essentially two typesof printers on the market, the dot-matrix type and the letter-qualitytype. There are also two methods of interfacing these printers to thepc-through a serial interface or through a parallel interface.The IBM printer, which is actually manufactured by Epson, is adot-matrix parallel printer, whereas most of the letter-qualityprinters from companies such as Nippon Electric (NEC) and Diabloare serial.The difference between a dot-matrix printer and a letter-qualityprinter is self-evident, although the difference between a serialinterface and a parallel interface is not-and is not well understoodby the average personal computer user. The difference lies in thenumber of bits of information transmitted at one time.Interfacial Bits. In a parallel interface the computer sendsinformation across eight parallel wires. This setup makes it possibleto transmit eight bits at a time. A serial interface sendsinformation serially, or one bit at a time. Obviously, the parallelmethod is faster, since it can send eight bits at once. However, theserial method is more common.There are two reasons for this apparent anomaly. The first isthat few computers use a. standard parallel interface, whereas mostcomputers have an interface card that allows use of the RS232-Cserial standard. Also, because of the nature of the circuitry required,serial lines can be run significantly longer than their correspondingparallel cousins-which means that noisy serial peripherals can beplaced in a room away from the computer.Therefore many peripheral equipment manufacturers offer theserial interface as a means of communication. This allows the use oftheir equipment on a large number of different computers.IBM offers what they call an Asynchronous CommunicationsAdapter, which is actually an RS232-C serial interface card. Thepurpose of this card, obviously, is to interface the pc to any of thegeneric peripherals that are available on the market. IBM does notsoftolk