Understanding Your Computer System

Your computer system consists of a Computer Box, Monitor, Keyboard, Printer, Surge Protector, connecting cables, Operating System, and Software.

Your computer, keyboard, monitor, printer, cables, and chips are called hardware. The programs, data, and operating systems are called software. Software that is stored in a chip such as a BIOS chip is called firmware. More on this later.

The computer box contains a main system circuit board on the bottom called a motherboard with a processor, system memory, expansion slots, BIOS, CMOS, a battery, and other support components on this motherboard. Also, a power supply, expansion cards, floppy drives and hard drives are in this box. In a 286, 386, or 486 system, there is usually a controller card that contains the hard and floppy drive controllers and serial and parallel ports. In a Pentium system, with plug and play, these controllers are on the motherboard so they can be controller by the computer's BIOS. The display card is usually an expansion card that plugs into an expansion slot of the motherboard. The monitor plugs into this card for its connection to the computer. On some manufacturer specific designs, the display circuits may be part of the motherboard circuits. This does not give you the ability to upgrade or replace a defective display circuit. The computer may also contain a CD ROM Drive, Sound Card, Modem, and Tape Backup Drive.

Intel is the largest manufacturer of processors and has set the pattern of growth and evolution over the years. Other processor manufacturers have cloned the Intel CPUs and if you are not using Intel, you MAY experience interesting annomolies.

The processor or CPU can be anything from an 8088, 286, 386 SX, 386DX, 486 SX, 486 DX, Pentium, Pentium Pro, Pentium II or Pentium III. Note that the motherboard is designed around the processor and that you can not install a 486 processor on a 386 motherboard or a Pentium onto a 486 board. Processors have evolved from 8 bit to 16 bit to 32 bit to 64 bit processors. These bits refer to the data path or BUS in the computer, from the processor to memory and expansion cards and back. This is a parallel path. The larger the bit path, the more data that can be passed at any one instance.

The original IBM PC and XT were 8 bit machines, while the AT 286 was a 16 bit machine. The 386 and 486 are 32 bit machines. All generations of Pentiums are 64 bit processors, as far as the data path is concerned.

Bits are on or off data signals, a 0 or 1, the smallest piece of information and actually the only information that computers understand. Computers count or compute with these zeros and ones. Eight bits make up a BYTE. A byte can represent a number or letter of the alphabet, a punction mark, or control character that only the computer or its equipment understands.

A computer with a 16 bit processor can process information twice as fast as a computer with an 8 bit processor. A 32 bit processor can process data twice as fast as a 16 bit processor or 4 times as fast as an 8 bit processor. The new Pentium processor processes data at 64 bits or twice as fast as a 32 bit processor or 8 times as much data in one clock cycle as an 8 bit PC or XT computer. Faster clock cycles in the newer computers, such as a 486 or Pentium, makes a much faster computer. Both the faster clock speed and larger bus determine how powerful a computer is.

The data path between the processor, memory, and expansion cards is called the bus. The bus between a 486 processor and the memory would be a 32 bit bus while the bus to the expansion cards can be 8, 16, or 32 bit. This means we can still plug in an 8 bit expansion card to a 486 processor that is 32 bit.

Computer design also allows for a second and optional processor called a co-processor. In the earlier PC and XT design, the co-processor was a 8087. In the 286 computer, it was an 80287. A co-processor was also made for both the 386SX and 386DX. The difference between a 486DX and a 486SX is that the 486DX contained a built-in co-processor. Note that it was not the case for the 386 SX & DX. The co-processor makes certain mathematical calculations and processing much faster. Programs had to be written to support a co- processor or it wouldn't make any improvement. Most programs writtten now take advantage of the built-in co-processor.

When the 386 computer was first released, it was very expensive. It is also necessary to use a 386 to run Windows 3.1 in enhanced mode. Intel developed a lower cost processor called the 386SX which was little more than a 286 with a 386 instruction set. Its bus was only 16 bits wide, but it allowed Windows to run in enhanced mode.

Your computer motherboard also contains several other note worthy components. One or two ROM memory chips contain a system BIOS which is the Basic In Out System or the first set of instructions that brings the computer to life. Typically, a BIOS, which is software in the chip, is licensed by AWARD, AMI, or Phoenix. These are the most popular BIOS manufacturers. The BIOS instructs the computer to test and turn on the various sections of the computer and as a finally, looks for an operating system such as DOS or WINDOWS 95/98 to complete its "boot-up" process.

Your computer has its configuration stored in a small memory called CMOS. This holds the time, date, amount of memory, how many and types of floppy drives, what type of display card, and the exact geometry of the hard drive. The geometry means the number of cylinders, heads, and sectors per track of the hard drive. The geometry times 512 K bytes is the exact amount of hard drive storage in bytes. As an example, a hard drive with 1024 cylinders, 16 heads, and 63 sectors per track times 512K equals 528,482,300 bytes or 528 MB (megabyte)s. The CMOS is kept alive by a battery. When this battery fails, your computer will fail to boot up. For this reason, you should be familiar with the exact geometry of your hard drive and other settings so that you can get your computer running again after your battery is replaced. These batteries usually last 2 to 5 years. Do NOT assume that the manufacturer or store made this information convenient for you. There are thousands of combinations of hard drive geometries by numerous manufacturers.

A "chipset" or group of 1 to 5 chips replaces many thousands of individual integrated circuits chips once found on earlier motherboards. This is also a personality of the computer. Intel is now the most common chipset on a Pentium computer. Intel also has several revisions of improved chipsets on newer motherboards. These chips are not replacable.

Computers are loaded with operating systems and programs from floppy disks. The most common floppy disk is the 3.5 inch high density 1.44 MB. Also somewhat common is the 5 1/4 inch high density 1.2 MB disk. This format seems to be disappearing though. Earlier floppy formats include 360K 5 1/4 inch double density and 720K 3.5 inch double density disks. You should not confuse these formats when purchasing blank disks. You should also note that high density disk drives were not supported in XT computers and many early 286 computers.

Hard Drives

A modern computer stores programs and data on a fixed or hard drive, or non removable drive as they are sometimes called. These drives range in sizes such as 10 MB, 20 MB, 30 MB, 40 MB, 80 MB, 104 MB, 200 MB, 345 MB, 420 MB, 528 MB, 850 MB, 1 GB, 1.2 GM, 1.6 GB, 2 GB, and even much larger. New computers usually have 1 GB or larger hard drives because newer operating systems, programs, and utilities are much larger. It's also easy to fill a hard drive because of the large variety of popular programs. Newer hard drives also operate much faster than the older ones. You should be aware that larger hard drives are also less efficient in storage space as larger clusters of sectors are required to obtain the larger sizes. 500 MB of data transferred to a 1.2 GB hard drive typically will take up 750 MB of space on the newer drive.

Hard drives can be divided into partitions. Years ago, there was a limit imposed by the way DOS 3.3 and lower was written and if you had a 42 MB hard drive, it could only have 33 MB as its largest partition. The drive had to be divided into 33MB and 9 MB or 21MB and 21 MB. This barrier was broken when DOS 4 and 5 was released. There is also a barrier at 528 MB. In order to break this barrier, either a software utility such as Disk Manager had to be loaded before DOS or the BIOS had to be upgraded to include what is called LBA mode (large block address). There is a newer barrier at 2.1 GB. This is either addressed with a software solution or a newer BIOS upgrade. Even if you use only one single partition, a partition table is written when the hard drive is prepared.

Hard drives have stacked magnetically coated platters with heads that read on both sides of them. Each platter has hundreds of invisable tracks (concentric circles). Each track is divided into sectors. There is a digital address at the start of each sector so that it can be located from a file allocation table. This file allocation table is constructed when the hard drive is formatted with DOS. DOS is placed on the hard drive immediately after formatting in the form of 3 files, usually IO.SYS, MSDOS.SYS, and COMMAND.COM. These are the 3 and only 3 files responsible for the hard drive to boot. All the other DOS files are utilities that come with DOS. If anything disturbs these 3 files, the partition table, the master boot record, the file allocation table, or the sector addresses, your hard drive gets corrupted so that it doesn't work corectly, if not at all.

Hard drives have had several types of different interfaces over the years. Earlier hard drives were MFM or RLL type interface. Another type called ESDI was improved butt expensive. The common types today are either IDE or SCSI. An IDE hard drive requires and IDE innterface. A SCSI hard drive requires a SCSI interface. They are not interchangable. You would damage a hard drive by using the wrong type controller. You should know what you have so you can upgrade or replace a failed drive. The older MFM and RLL and ESDI and not used any longer and if you are using any of these, you will need to change over completely.

System Memory

A computer uses system memory to actually run and calculate from. These are usually memory modules in modern computers rather than individual memory chips. The first PCs only came with 512K or 640K system memory. Windows 3.1 actually requires 4 MB minimum with 8-16 MB recommended. Windows 95 wants 16mb and Windows 98 wants 32 mb. Actually, you should have twice that amount. The computer will run much faster and more efficiently with that doubled amount. Windows does not run out of memory as long as there is hard drive space available, as it swaps to the hard drive. An out of memory message comes from the 640K convention memory not being managed. System memory operates much faster than hard drive memory. All processing is done from the system memory and created data is stored back to the hard drive.

The operating system usually loads into the lower 640 K memory when the computer is booted. System drivers are loaded next, and then the programs. The memory area between 0 and 640 K is very critical to set up properly. New and larger programs require that most of DOS and drivers be loaded into special high memory areas to make room for programs in the 640 region. DOS programs usually only run in the first 640K area. If DOS and drivers take up too much of this area, these newer and larger programs won't run, no matter how much memory you put in your computer. Typing MEM at the DOS C: prompt can tell you how effeciently your system is setup. If your memory available to programs is less than 620K, you are asking for trouble. If you are running DOS, run MEMMAKER to attempt to set your system up properly. You can not do this in Windows 95/98.

You must understand computer memory in another way if you work on your computer. Memory chips or modules are installed in banks or groups. In a 32 bit 386 or 486 computer, memory is added in banks of 4 SIM Modules to get the width of 32 bits. Anything less means you don't have a 32 bit memory system. In a Pentium system which is 64 bit, you add memory in banks of either 2 72 pin Simms or one 64 bit DIMM. Many low end computers such as the 586 (which is not Intel) is really only a 32 bit system and you add memory as one 72 pin or 4 30 pin modules. If you do not have a clone type computer, be aware that you will probably require specially wired and proprietary SIMM modules. Also be aware that many of these have shown up at computer shows and plugging in these wrong modules to the wrong type computer can destroy a motherboard. In the converse, the generic SIMMs can also destroy propritary computers.

You should also know what type memory your computer uses. There is parity, non parity, and EDO memory. Parity memory can check itself for errors. Non parity does not check it self. EDO is a bit faster but has no parity check. There are many companies cranking out poor quality memory now and when something goes wrong, you may not get an indication of what's causing lockups. Many newer computers also do not allow for parity check memory because memory is supposed to be of better quality, but that's not always the case. You should know the company who sold you memory, who the manufacturer is, and the return policy. A computer show can be a disasterous place to buy memory. You get what you pay for.

Software Drivers

The PC Computer is a very flexible system. There are many choices of hardware manufacturers, both for the computer and for all the various components. Each of the manufacturers advances technology when they try to outdo the other with their own new technology and features. This competition helps keep costs low too. Because we have this variety, there can also be problems of interfacing each device to work with the computer system.

Beside the main computer, we have choices of different display cards by different manufacturers, controllers, ports, mouse, printers, CD ROM drives, sound cards, scanners, hard drives, and many others. To make each work with the computer system, there is a software driver that makes the device compatible with the system. For instance, the display card operates only in its default mode of operation until a software driver makes it go into a different mode of resolution. You choose when you want a certain mode and specify that driver. For example, Windows operates in standard VGA mode unless another driver is installed. It doesn't happen automatically. We recommend installing the 640 by 480 resolution at 256 colors driver so that multimedia works in Windows. A Driver disk that contains these drivers comes with every display card or computer system. Don't loose track of it.

Software drivers are small software programs to interface specific hardware additions to the main hardware or other software. Each manufacturer designs new and special features into their equipment. That gives you choices and allows technology to further develope.

If you use a Microsoft mouse, a microsoft mouse driver must be installed for both DOS and Windows. If you switch to a Logitech mouse, you must change the software driver. They are not interchangable.

Your printer requires a print driver. Numerous ones come with Windows, Word Perfect, and other programs and you select them at installation. Since many new printers are manufactured after a program comes out, manufacturers of printers sometimes supply the driver on a disk with the printer. You should locate all your books and sheets and driver disks as you obtain equipment and keep them in a separate place where you can find them when you need them. Even make copies. Most computer users loose track of their disks and books. Do you?

CD ROMS, sound cards, and scanners are more complicated. The drivers are essential to their operation. You can also run into interference between devices. As you install devices into your computer, you should keep a chart of their addresses. Do this from the start. It will become fustrating if you buy something new and have to scramble for information on previously installed devices. Don't loose your driver disks. Make copies and know where they are.


Display cards plug into an expansion slot in most computers. It is the interface between the computer and the monitor which you view your computer information on. Early technology only gave users monochrome or simply a gerrn or amber screen. Technology advanced to color and CGA gave us only 4 colors and low resolution. Newer technology advanced to EGA with 16 colors and better resolution. These previous technologies used a digital signal and a 9 pin cable between the display card and monitor. They were not compatible with each other to be interchanged. The newest technology is VGA and SVGA which uses a 15 pin cable plug and an anaolg signal as compared to the previous digital signal. Analog can give up to 256, 32000, or even 16 million colors depending on individual card capability and resolutions of 640 by 480, 800 by 600, 1024 by 768 and higher. These new cards also have their own memory of at least 1 MB. A display card that does 256 colors at 1024 resolution will surfice for most computer users. It should also do 64 million colors at 640 resolution if you are interested in "photo cd".

Display monitors are usually 14 inch diagonal as measured on the picture tube. 14 inch monitors measure about 12.5 inches as usuable area. 15 inch monitors are becoming more popular, but have about 13.5 inches of usuable area. Good monitors will have a dot pitch of .28 as apposed to .29, .31, .39, .41, or .52. This is the smallest dot made up of the red, green, and blue pixel. The term super VGA has been misused. Super VGA can be 640 by 480 lines by an old definition. You want a monitor that can display 1024 by 768 lines. Better monitors will also have "non-interlaced" at 1024 by 768 capability. This is only a factor at high resolutions.

Keyboards can be a personal item. Different manufacturer's keyboards may have a different feel to the touch. Some even have a click feel. A beginner rarely can feel the difference but an experienced typest should test the keyboard for the proper feel. An old keyboard from the original IBM XT or PC is not compatible with the scan codes of newer keyboards from 286-386-486 computers. Be careful about interchanging them. Never pull the plug of a keyboard with the power turned on. This will cause damage to the computer that will not be covered by warranty.

Surge Protectors are a necessity for a computer system. Purchase only a good quality protector that has a manufacturers address. Good protectors will give you a warranty and insurance in the event of a surge. Any protector under $20 is quite questionable in quality. They usually blow and take your computer with it. Although homeowners might cover damage, you usually have a deductable. Beware, that many insurance companies exclude computer coverage that has business programs on them, unless you obtain an add-on to your policy. We recommend a Panamax surge protector. The warranty will also protect your equipment.


CD ROM drives and sound cards are very desirable add-ons. They come with numerous specifications from the various manufacturers. They come in double speed (2X), quad speed (4X), six speed (6X), 8 speed (8X), and now 12X. This refers to the data transfer speed. These speeds are based on single speed being 150 KB per second transfer. There were several generations before this that were slow and slower. Beware that double speed isn't twice the slowest found in some bargain shops. You might also look at the average access speed. Few realize this can be an important factor. Choosing one with an access speed under 200 ms or lower is the best. You should be aware of the type of interface card required. The better drives seem to come with SCSI interfaces and these require expensive controllers. Multisession Photo CD, MPCII, and XA compatibility are necessary. New formats for video CD are just around the corner. This will evolve with single sided and then double sided formats. Your CD ROM Drive is already outdated, even if you buy the newest one.

Choose a 16 bit sound card. Don't be fooled by names and designators like PRO. The Sound Blaster 16 is our best recomendation. The sound blaster 32 is not a 32 bit card. It is only 16 bit and has 32 voices. It is a step up though.


A modem is also an important accessory if you plan to surf the net. A modem is a device that takes your data to or from a serial port and converts it to or from tones that can be carried over a phone line. Internal modems seem to be more popular since they go inside your computer and do not take up space on your desk. More professionals prefer external modems because they can see the light display to watch call progression or problems. The speaker is usually heard better on these, and there is better isolation between computer circuitry should an electrical problem cause damage to the serial port or computer. The 28-8 or 33 k modems are a minimum with 56K modems recommended since they have dropped in price and are essential to using the Internet. Note that many 56K modems do NOT work at 56K due to phone line limitations. There are also incompatibilities with many cheap modems.

Newer modem standards are fast gaining popularity. ISDN is an all digital modem that operates at 64 or 128 KB per second. These new modems require an ISDN phone line from Bell which isn't all that expensive when you consider you get 2 line appearances (2 numbers) and you can do voice and data at the same time. DSL is also now coming into use and that is faster and cheaper yet.

Operating Systems

MS DOS 6.22 with Windows 3.11 as an environment is very stable and right for most users. Windows 95, a combined operating system and enviroment, has been out since August 1995. It is a 32 bit system and you should be aware of some information about it. If you are buying a new system with all new software, you will be much better off than upgrading. Most of your trouble will start if you put older software in with it. When Windows 95 goes flukkey, you can expect to "pay" for support. Your best choice may be to start over and reload all. Those that have paid for the certified course will charge typically $90 to $150 per hour for this support. You can expect a minimum of several hours. This is where backups are important but also be aware that backing up and restoring Windows 95 is complicated. To restore, you must first reload Windows 95 and then the backup/restore utility. Then you can pray that the backup doesn't contain the problems that started your trouble. It is actually best to reinstall all your programs from scratch and then restore only data files. Windows 98 is the same. Make sure you get Windows 98 Second Edition as the first edition had numerous bugs.

Windows NT 4.0 is available and much more stable, but many drivers and programs are not available for it yet. It's also much more expensive. There is also UNIX and Concurrent DOS for operating systems, but they are very expensive and require professional support. Windows 2000 is NT 5.0. It is NOT for everyone. Windows Millinium will be out in the fall of 2000 and that is the next upgrade for 95/98 users, not Windows 2000. Also watch out for a 64 bit version of Windows 2000. It requires the new 64bit processor.

Disappearing Data

You must backup your data regularly. Your hard drive is very intricate and can die or scramble data at any time. Although they can last 2 to 5 years, many die before their warranty is up. Accidental erasure or the installation of a new program or utility can also make your data disappear or scramble. Your backup plan should even include rotating backups because they can fail. Your backup plan should include full backups during certain phases of your plan. Do you know how to restore your backups? Are you backing up the right stuff?

How to Destroy Your Computer

Your computer system can easily be destroyed. Besides surges, theft, and accidental dropping, static electricity is a killer too. The following list will also give you an idea of how computers are ruined: floppies shoved into drives upside down, plugging in or removing the keyboard with the power on, jaring your computer while turned on, connecting parallel printers to serial ports with wrong cables and adapters, allowing dust to buildup inside the computer, or connecting a wrong type of monitor with a wrong adapter to a wrong type of display card. If you go inside, additional trouble awaits you if you: connect a hard drive cable backwards to to a floppy controller, connect a ribbon cable backwards or miss a row or column of pins on a floppy drive, install the wrong type of memory or insert it backwards, insert or remove expansion cards with the power turned on.

Static electricity is the most common killer: If you move your computer so you have to reconnect it, always turn the power switch off, then pull the plugs with the power being last. When reconnecting, make sure the power switch is off and then PLUG IN THE POWER CABLE FIRST so as to put a ground on the computer chassis. Then reconnect the other components. Many computers have their display cards and ports blow, if not the whole system, because of a static charge connecting the monitor or keyboards or printer first before grounding the system. This accounts for many "dead out of the box" new computers.

This Document Copyright 1995-1996 Gene's Computer Outlet, Inc No part may be reproduced without the expressed written permission.