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The Personal Computer System
This page is all about the personal computer as a system, from the original
IBM PC to modern PC clones.
Introduction
The PC, universally referred to as any IBM compatible computer, drastically
changed the role of computers, from an as needed, as available managed computer
too a growing and accelerating industry. Basic PC hardware can almost do nothing
without complex instructions. Even today's powerful hardware merely performs a
power on self test and load the first bit of data from the disk. To successfully
use a personal computer requires some expertise. Writing computer programs can
develop better understanding of how computers do what they do and an insight
into applications used on a computer. In the early days of personal computers
BASIC (Beginners All-Purpose Symbolic Instruction Code) was part of the system
and primarily used to instruct the computer to perform operations. Many early
applications were written in BASIC. Learning how complex tasks can be programmed
as instructions, then refined, helps to understand how computers work. There are
background instructions keeping the computer functioning, input and output
processing, in case of key presses or mouse movements and screen updates.
Versions of BASIC are still used today. QBASIC is still supplied free within
MS-DOS and Visual BASIC is used to design applications with the same user
interface as Windows. This guide is intended to be about personal computer
hardware and so it is left for the reader to pursue any programming skills.
A basic computer has four key components, the CPU (Central Processing Unit) or
processor, input and output (I/O) expansion such as keyboard, display and disk
storage. Other components primarily support them, such as the motherboard,
buses, expansion cards or power supply unit. The motherboard brings together
individual boards that used to be housed separately, before personal computers.
The processor, memory, serial ports, parallel port, keyboard interface, disk
interface and buses. The processor executes instructions at low level and knows
how to add subtract and simple logical functions. The computers memory is
workspace for all activity and is limited by the size. The number and variety of
applications that can be made available at any one time is largely determined by
the amount of memory, usually in megabytes (MB), millions of bytes (kilobytes
are thousands of bytes, KB). Input and output (I/O) is used by the computer to
read and write data using I/O devices called peripherals, including the monitor,
printer or storage devices. Storage devices are used to keep data stored, when
it is not in the computers memory.
A Brief History
In August of 1981 IBM officially announced the Personal Computer (PC). At the
time, many disagreed on the success of IBM selling computers to the public
through IBM's stores and distributors. It was also predicted by some staff at
IBM that because of the shady and unreliable design of the PC and the fact that
it had not undergone any of IBM's quality tests and design procedures, no one
would won't to buy the computer.
One of the best things about IBM's personal computer was the Open System
attitude of the designers, who knew that by making a full listing of the system
BIOS and internal design and specification schematics readily available, third
party manufacturers and designers could build expansion cards, peripheral
devices and even clone systems. This would make the PC a much more viable tool
in a field already swamped with 8 bit computers. IBM took measures to insure the
hardware design remained theirs, and patented the ROM BIOS and other hardware.
The PC was shipped with an operating system called PC DOS, ported to the PC from
QDOS, purchased from Seattle Computer Products by Microsoft (then Bill Gates and
Paul Allen).
The first PCs were shipped in desktop cases, housing full sized motherboards with Intel 8088 processors, 1 MB of surface mounted memory, a BIOS but no real time clock (RTC) or battery backed CMOS, an expansion card for output to a monitor (usually monochrome or amber although colour was supported), a keyboard controller and keyboard but no numeric keypad, a single single sided double density 5.25" floppy drive and floppy disk controller, a parallel port and two serial ports and a copy of DOS. The motherboard offered in total eight expansion slots for input/output devices although some would already be in use. Printers where available, the most common were daisy wheel which struck against a typewriter ribbon to leave an impression on the paper which was feed through a roller by sprockets which aligned with holes along the edge of the printer paper which was fanfold.
Everything about the PC was focused mainly on an office environment and mimicked the `functions and procedures of tasks carried out by the workforce. Tasks such as typing letters (word processing), keeping records and files (database) and working with tables or charts (spreadsheets and graphics). Systems analysts and/or programmers would create a logical representation of the flow, inputs, processes or functions and outputs of the business and
(try) build a logical working computerised model of the business.
As the PC and software gained popularity more software and hardware manufacturers produced for it. Some of the most useful expansion cards for the original PC were the real time clock and the hard disk controller. The real time clock allowed the computer to keep track of the date and time once booted to the operating system and hard disk drives originally built by western digital and controller cards to operate the device which enables operating systems, applications and data to be stored on one disk. Once the hard disk appeared for the PC software houses supplied software that could be installed to the hard disk instead of running from floppy drive, no more floppy disk swapping.
The first breakthrough to make a difference to users was more RAM from 1 MB to a possible 16 MB of system RAM. Two main standards competed to become de facto, extended memory and expanded memory, both incompatible with the other and in the beginning could not operate at the same time in the same system. Software houses supplied versions of programs that utilized this extra memory, often as data workspace, and so the PC was able to run more powerful applications and use more data, quicker in the process, because there was no need to
sort or fetch it from disk. Keyboards started to appear with numeric keypads and shortly after the release of Microsoft Windows pointing devices such as track balls, joy pads and mice became popular. Earlier versions of Windows were not as useful as the enhanced mode offered by version 3.0 which allowed the processor to switch to a mode that would allow multiple applications to execute simultaneously sharing system devices and resources and eventually data. This meant that a word processor could be started and also a database application etc, as long as there was enough resources, also RAM was not restricted to physical quantity as the hard disk could be used to page (move) working data to and from the drive as required.
One of the best features of the Microsoft Windows front end was allowing hardware manufacturers to supply a driver that only needed to work in one program, namely windows, which software writers could access from within applications, without needing to know how to actually program that
devices low level functions. As long as a programmer could tell windows what to print or display the driver would know how to instruct the hardware. No more loading drivers into every application that
accessed a piece of hardware. Soundcards soon appeared, as the next useful addition that would take up a free slot and an IRQ. Adding multimedia capability to the PC literally made it all singing and all dancing. Around the same time higher resolution and deeper colour depth, graphics cards and monitors where appearing. The expansion slots and the cards that populated them advanced from 8 bit cards to 32 bit bus mastering devices capable of talking to any other device, the system RAM or operating system without the need for the CPU's intervention.
A pattern emerged, where the hardware demands of software was pushing advances
in designs, manufacturing and eventual sale of computers hardware. Every
computer manufacturer in all sectors strived to be the company to emerge with
the next mind blowing, got to have it, voted to be, industry standard computer
upgrade (The same went for software houses). As a result of all the new
technology changes consumers became paranoid when purchasing for fear of being
sold old technology, and when Microsoft changed the naming convention of all
their software from version xyz, to 9x (the year released), it drove home the
true meaning of out of date. Another problem to emerge from the rapid advances
was dead end systems, which had no or limited upgrade-ability. Every time Intel
released a new processor, a new motherboard and support components were utilised,
causing frustration to system up-graders. Purchasing a new motherboard also
meant buying new RAM, graphics card, hard disk, etc, if the new technology was
to be fully implemented (Some manufacturers maintained more backward compatibility
than others, based on the market they were trying to sell too). The original
message from IBM, that your personal computer will never be obsolete, is based
on the fundamental principle of backward compatibility (but not necessarily
forward compatabilty). A good thing and a bad thing. New technological advances
sometimes mean breaking away from the way things are normally done and thus end
the backward compatibility, unless some careful thought is put into the planning
and implementation. Backward compatibility is a good thing if newer personal
computers can use old hardware, however this hinders ideas for breakthrough's if
no choice can be found to upgrade and implement the original IBM PC design.
Manufacturers have been caught out in the past, trying to lead the way only to
be bowled over or left behind by rapid advances. Designs were out of date before
they were even completed. It was traditional to follow Intel and for a long time
they determined the speed and direction of the personal computer, but all along,
in the background was the consumer, who could make or break upgrades. Being the
first to release to the consumers also meant oldest technology, design, features
and more important components used in the manufacturing were old. Some designs
chose to use the latest, untested components and others stuck with what they
knew. Success became more dependent on how many people used the product. A new
trend appeared, manufacturers were releasing products into the consumer market
that had neither been properly tested nor rigorously used with existing designs,
in there rush to release products (again the same went for software houses), get
the picture ?.
Hard drive capacities have increased along with speed and reliability, allowing
more business critical applications and data to be implemented on the PC.
Software houses added more functionality to their programs and installing them
on to computer often meant feeding dozens of floppy disks in to the drive, an
incentive to utilise the CD-Rom technology utilised by the music recording
industry. Bigger and better software products soon emerged. Some merely included
massive movies and rolling intros, but who could blame them given all that
space. It was not long before CR writers became popular and soon everyone was
copying there own data to CD. Distributing data on this form of media became the
standard adopted by most publishers. Flatbed scanners also drastically advanced
in design and as a result, are more cheaply and readily available as a useful
upgrade to import data from the physical world in to electronic representation.
Printer designs changed from impact designs to inkjet and laser technology.
Sound cards have added three dimensional and realism to multimedia and the AGP
graphics card has once again put the PC in front of the games playing consoles
(and always will, if manufacturers strive to maintain backward compatabilty with
every addition of new design.
Today, the present memory technology and design can not supply processors fast enough
and is, the major bottleneck in the PC system.
To be continued...
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