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         INTRODUCTION TO COMPUTER TECHNOLOGY - INPUT, STORAGE, OUTPUT 

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       Before we examine computer technology let's cover two items 
       which seem to confuse EVERY computer beginner. It's a wonder 
       computer manufacturers don't include these two ESSENTIAL points 
       in instruction books. 
       
       First item: Booting.
       
       Many times an instruction manual refers to "booting up" or 
       "booting DOS" before you can start a program. This means 
       inserting your DOS diskette in a floppy drive and starting the 
       machine with the DOS diskette in place. When you see the 
       familiar A> or C> prompt symbol, you have booted up! If you have 
       a hard drive which starts the machine automatically, the hard 
       drive "boots DOS" for you and you do NOT need to use the DOS 
       diskette. This seems simple, but many beginners are confused by 
       the term "booting up." 
       
       Second item: Working with floppy diskettes. 
       
       A standard floppy diskette is either 5 1/4 inches or 3 and 1/2 
       inches square. To insert a floppy diskette into your computer 
       drive, first remove it from the paper or plastic slipcover if 
       one protects it. The proper way to insert a floppy diskette in 
       most drives is as follows.
       
       For larger 5 - 1/4 inch floppies, turn the printed label side up 
       and locate the TWO VERY TINY notches along one edge. Near the 
       notches will be a jelly bean shaped hole about one inch long cut 
       into the plastic surface of the diskette. This oblong hole is 
       the read/write opening. Insert the diskette into the drive with 
       the label side up and the two tiny notches FIRST into the drive 
       opening then close the drive locking handle. Along one edge of 
       the diskette you will also see a SINGLE square shaped hole which 
       is the write protect notch. If this write protect notch is 
       UNCOVERED you can BOTH read and write data to the diskette. If 
       the write protect notch is covered with a piece of tape, then 
       you can READ information from the diskette but you CANNOT write 
       information to the diskette. This is a safeguard feature you may 
       wish to use from time to time. Keep fragile diskettes away from 
       smoke, hair, dirt and ESPECIALLY sources of magnetism such as 
       motors, loudspeakers or even childrens magnetic toys which may 
       ERASE your data! 

       For smaller 3 - 1/2 inch size diskettes, turn the label side up 
       and locate the metal "shutter". Insert the diskette into the 
       drive with the label up and the shutter FIRST into the drive. 
       The write protect notch or opening is a small square hole with a 
       SLIDING PLASTIC TAB which is slid CLOSED (cannot see an open 
       hole) to enable BOTH reading and writing to the diskette. The 
       sliding tab is placed OPEN (visible open hole) to enable reading 
       but NOT writing.

       Here is how to tell the different densities of various diskettes 
       your computer might need: a standard 5 - 1/4 inch, 360K 
       (Kilobyte) diskette has a plastic reinforcing ring around the 
       center hole. A 1.2MB (Megabyte) diskette does not. Small 3 - 1/2 
       inch, 720K diskettes have one small notch cut in the plastic 
       diskette casing while 1.44MB diskettes have two notches. 
              
       Time to move on to basic computer technology . . .

       Computers vary widely in size and use. However all computers are 
       similar in what the hardware does. So-called microcomputers 
       (like your desktop pc) are designed for personal use, relatively 
       low price, and modest data processing tasks. Minicomputers are 
       moderate sized (a small refrigerator size) and perform more 
       complex tasks with larger amounts of data. Minicomputers might 
       be used in a small engineering office or a local bank branch to 
       send transaction data to a head office computer. Mainframe 
       computers are large, expensive and process billions of 
       characters of data rapidly and fill entire rooms. Finally 
       supercomputers are built to minimize distance between circuit 
       boards and operate at very high speed for complex uses such as 
       designing airplanes, animating complex movie sequences 
       graphically or solving complex engineering formulas having 
       billions of steps mathematically. Supercomputers are built for 
       raw speed. 

       Some terms apply to all computers. INPUT is how data gets into a 
       computer. The keyboard and mouse are familiar INPUT devices. 
       OUTPUT references how data is provided from the computer. A 
       Monitor or printer are good examples of OUTPUT devices. PRIMARY 
       STORAGE or MEMORY is the computer's immediate data storage area 
       - usually this is in small integrated circuit chips which hold 
       data ONLY while power is supplied. This PRIMARY STORAGE area is 
       thus temporary. More permanent SECONDARY STORAGE is used when 
       computer power is off or when data overflows primary storage. 
       This is usually floppy or hard disk drives but can include paper 
       tapes, punch cards, or even non-volatile magnetic bubble 
       memories. 

       How do computers store data and programs? For the PC (personal 
       computer) storage of data can take place either in an integrated 
       circuit chip or IC when the machine is on or a magnetic disk 
       when the machine is turned off. 

       The magnetic disk used to store information works in a manner 
       similar to a tape recorder - magnetic impressions are placed on 
       the tape and can be later replayed. Magnetic sound tape as a 
       long strip of plastic with a thin coating of a metallic, easily 
       magnetized powder glued to the surface of the plastic strip. 
       When a electrically driven coil is placed near the surface of 
       the plastic strip, thousands of little magnets are created on 
       the surface of the tape as it rapidly streams beneath the coil. 
       Later these little magnets can induce current to flow in the 
       coil as the tape is pulled past the coil a second time. Thus the 
       information or music is replayed. During recording, the 
       electrical coil receives electric pulses which produce small 
       magnetic "blips" along the tape. During playback, the coil is 
       passive and the little magnetic pulses passing below its surface 
       create electric pulses in the coil which are amplified. 

       A magnetic computer disk works in the same fashion but spins in 
       a circle like a music record rather than moving in a straight 
       line like recording tape. Magnetic computer disks are available 
       in two basic types: floppy and hard disks. A hard disk can hold 
       considerably more information than a floppy disk - frequently 
       millions of computer words (or "bytes") while a floppy disk 
       holds less than a million in many cases. However what the floppy 
       disk loses in capacity in gains in the advantage of portability 
       since it can easily be removed from the pc and stored which is 
       not true of the hard disk. 
              
       On a typical music cassette tape you will find two channels 
       (left and right speakers) and a total of four tracks (side A of 
       the tape and side B.) Think of this as four lines of 
       "information" running the length of the music tape. On a 
       computer disk data is stored in a similar manner except there 
       are far more tracks of information and of course the tracks are 
       arranged in circles on a flat surface like a music record or 
       compact CD disk. 

       Tracks of computer information are written to and read from the 
       computer disk by a read/write coil (head) that moves rapidly 
       across the surface of the disk in a fashion similar to a record 
       player needle on a music record. Most current disks (360K IBM 
       format) have 40 tracks which are numbered from 0 to 39. The low 
       numbers are towards the edge of the disk - the high numbers 
       towards the center. 

       Tracks, the circular data paths on the disk, are divided into 
       still smaller units called sectors with the number of sectors 
       varying with the exact DOS operating system you use on your PC. 
       MS-DOS version 2.0 and higher versions use nine sectors per 
       track. DOS 2.0 and above can read the older eight sector disks 
       created by DOS version 1.1 but the reverse is not true. Each 
       track is divided into the same number of sectors like pieces of 
       apple pie. The sectors contain the magnetic bits or pulses of 
       information which the computer records in a special index 
       (called the file allocation table or FAT) so that it can quickly 
       move from sector to sector sniffing out information on the disk. 

       When you format a disk you ask the computer to inspect the 
       magnetic surface of the disk for any errors, prepare it for use 
       by future data and create an index "file allocation table (FAT)" 
       which is like a card index for a large library of books. 
       Formatting a disk is a little like taking a blank piece of paper 
       and using a pencil and ruler to turn it into graph paper with 
       both horizontal and vertical lines. What was blank before now 
       has little cells or file drawers which can hold information. 

       The file allocation table is so crucial to keeping track of 
       where the data is on the disk that DOS (the disk operating 
       system) usually keeps two copies in case of errors. Without a 
       file allocation table the disk is like a large public library 
       with no card catalog index and (worse still) every light in the 
       building has been turned off! Certain utilities contained in DOS 
       (i.e., the debug utility) and other software programs can adjust 
       or repair the file allocation table but generally this is a 
       delicate operation a beginner should not attempt. 

       Floppy disks are available in two types: single and double 
       sided. This means that the manufacturer guarantees only one (or 
       both) sides of the disk as capable of holding magnetic pulses. 
       Usually both sides of all disks are chemically coated, but the 
       manufacturer may have found defects and advises use of only one 
       side. IBM compatible machines usually use double sided, double 
       density disks (abbreviated as DSDD on the package.) Single 
       density disks record magnetic pulses or computer bits at 2,768 
       bits per inch and double density at 5,876 bits per inch. A 
       single sided disk may work in a machine for a while, but you DO 
       stand a risk that the data may be lost in time on the second 
       "non-certified" side of a single sided disk. Do NOT turn over a 
       disk and attempt to use the other side! Two problems arise: the 
       disk spins in the opposite direction which may cause data errors 
       and the small write protect notch is in the wrong location which 
       may damage the floppy drive mechanism. 
              
       What is the difference between a bit and a byte? The IBM PC and 
       its clones generally use 8 bits (electrical pulses) to make up 
       a byte (computer word.) A ninth "odd bit" is used for error 
       checking (parity testing) to make sure the other eight bits are 
       not accidentally erased or lost during storage or use by the 
       computer.

       Bits are like alphabet characters and bytes are like the words 
       made up from alphabet characters. So how many bytes are stored 
       on a floppy disk? 40 tracks per side x 2 sides per disk x 9 sectors 
       per track x 512 bytes per sector = 368,640 bytes stored per disk 
       assuming DOS version 2.0 or later. Basically this means about one 
       third of a million pieces of data information - quite a bit! 

       On the side of all floppy disks is a small square notch. If the 
       notch is uncovered, data can be freely written to the disk. If 
       covered with tape, the PC will NOT write to the disk but CAN 
       read from the disk. This is called the write protect tab. Be 
       careful when handling disks! Since the read/write magnetic head 
       on a floppy rides delicately in contact with the disk, tiny 
       obstructions can cause it to jump, skip or scratch the disk and 
       lose your data. Fingerprints, smoke, hair and moisture can cause 
       problems. Always handle a floppy disk by the edges of its 
       protective plastic "jacket" and replace it in a paper or plastic 
       Tyvek slipcover sleeve when not in use. In addition, magnets, x-
       rays, televisions and other sources of stray magnetism can cause 
       a floppy disk to lose data. 

       Hard disks have many of the same characteristics as floppy 
       disks, but are managed and maintained in a different manner as 
       we will see in a later expanded tutorial on hard disks within 
       package. In brief, however, hard disks use aluminum or hardened 
       glass platters rather than flexible plastic mylar. Usually 
       several platters are stacked together within a single hard drive 
       unit. The number of stacked platters determine the data capacity 
       of the hard drive unit. Because the hard disk platter spins much 
       faster and holds data packed more tightly that a floppy disk, 
       the hard drive unit is usually sealed in a metal shroud or 
       container to eliminate dust or other contaminants. A sealed hard 
       drive is sometimes referred to as a Winchester disk or Fixed 
       drive. Where a floppy disk might hold approximately 360,000 
       bytes (abbreviated as 360K), a hard drive holds 10 Megabytes 
       (million bytes) or more. As we will discuss later, backing up 
       (making spare copies of hard drive data onto floppy or tape) is 
       a necessary task since hard drives can and do fail - taking 
       precious data with them. The bottom line is that once you get 
       started with a computer, quite quickly your data becomes far 
       more valuable than the computer in which it resides! 

       Since we have briefly covered data storage we need to talk about 
       data input. Two primary input devices are central to getting 
       data into a pc. The keyboard and the mouse. We will discuss the 
       keyboard in greater detail in a later tutorial. The mouse is an 
       alternate input device which is rolled or moved across the 
       desktop to position a cursor or pointer on the computer screen. 
       The mouse also contains several buttons to help select items on 
       data on the monitor screen. A mouse is not necessary for 
       computer input - it is an optional device. 

       Another introductory topic is that of output devices such as a 
       monitor, printer or plotter. 

       A plotter is a device which uses a motor to move pens or drawing 
       implements in tightly controlled horizontal and vertical motions 
       on a piece of paper or film. The computer can control a plotter 
       to combine on one piece of paper differing pen colors and text 
       and pictures stored within the computer. Computer plotter can be 
       purchased with flat table or flat bed configurations or in 
       models which move the pen(s) back and forth with gears that also 
       drive the paper movement at the same time. 

       The printer is probably the most common and useful output device 
       attached to your computer. There are many types of modern 
       computer printer with differing speeds and capabilities. The 
       most common printer is the dot matrix printer which provides 
       characters made up from tiny dots of ink on paper. The Daisy 
       wheel printer uses a rapidly spinning wheel to imprint each 
       letter separately like any ordinary typewriter. Line printers 
       print entire lines of text in one sweep then move to the next 
       line and are thus very fast. Ink jet printers produce characters 
       made from individual dots of ink sprayed onto the paper. Thermal 
       printers contain tiny wires which burn and thus darken special 
       thermal paper into tiny letters and dots which we can read. 
       Finally laser printers use a rapidly scanning laser to sensitize 
       a polished drum with an entire page of information quickly and 
       look and work roughly like an office copier. The first three 
       types of printer are classified as impact printers since 
       something strikes the paper which the later three are non impact 
       printers. 

       The oldest printer design is the thermal printer which 
       maintained some popularity and was easy to manufacture, however 
       the use of thermal printers is fading since the special heat 
       sensitive paper is expensive and subject to random extraneous 
       marks and blurring. 

       The laser and ink jet printers are becoming more popular due to 
       rapid speed of printing and quiet mode of operation. They are 
       expensive with prices ranging from $600 to $2000. The ink jet 
       printer squirts individual dots of ink onto the paper to form 
       letters or other characters. A high quality paper is necessary 
       since the wet ink can smear if not carefully handled. 

       The laser printer is used for quickly producing one page of text 
       at a time. In operation, the laser scans a polished drum with an 
       image which is then dusted with dark toner particles which stick 
       to the exposed areas made sensitive by the laser. Paper is then 
       placed in contact with the drum and the toner is transferred to 
       the page and is finally fused with heat to "fix" or seal the 
       toner particles to the page. 

       Dot matrix and daisy wheel printers are common and affordable 
       alternatives for many small offices and home computer hobbyists. 
       The two differ in the sharpness and quality of the final printed 
       document. 

       Dot matrix printers produce letters via small pins which strike 
       the ink ribbon and paper to produce print which can be jagged 
       looking. Nine pin dot matrix printers produce somewhat rough 
       looking letters while 24 pin dot matrix printers produce 
       crisper, fully-formed letters. In many cases the 24 pin dot 
       matrix printer approaches the quality of the daisy wheel printer 
       which seems to be fading from the computer printer scene. Both 
       dot matrix and daisy wheel printers strike the paper through a 
       ribbon to transfer ink to the printed page. 

       Connecting a printer via a cable to the computer is always done 
       through one of two plugs (or interfaces) on the back of the 
       computer. One type of interface (computer plug) is serial, the 
       other called parallel. The most commonly used interface for 
       printers today is the parallel interface but serial interface 
       printers do exist. What is the difference? Recall that there are 
       eight bits (computer dots and dashes) to a byte (or computer 
       word). The serial interface has each bit sent one at a time to 
       the printer - like men in single file at the supermarket 
       checkstand. The parallel interface sends all eight bits at once 
       - like eight men all entering eight supermarket checkstands at 
       once. Each interface is different, the printer manufacturer will 
       tell you which interface to use. As a clue, frequently modems or 
       mouse devices use the serial interface leaving the printer to 
       the parallel interface. 

       We have talked about output to paper, next let's briefly discuss 
       output to a monitor or screen. The monitor or video display 
       works much like your television - some older home computers 
       still use a TV. Another term for a monitor is the cathode ray 
       tube or CRT. Monitors differ in the sharpness or resolution they 
       can display. On the low end of the resolution spectrum is the 
       monochrome (single color) monitor frequently available in either 
       green or amber screens. Next is the color RGB monitor (RGB 
       stands for Red, Green and Blue) which displays low resolution 
       color dots to make up an image. Higher resolution is obtained 
       with an EGA monitor (Enhanced Graphics Adapter) and still higher 
       with a VGA (Video Graphics Array) Monitor. Each monitor is mated 
       to work with a circuit card located within the body of the 
       computer. One way to upgrade a computer is to switch both the 
       monitor and display/graphics circuit card to produce a sharper, 
       more colorful image. The dots which make up all images on the 
       monitor screen are called pixels. The smaller the pixels, the 
       higher and sharper the image resolution. 
  
       What is the difference between computer hardware and software? 
       In simplest terms, hardware is the physical parts associated 
       with a computer - the circuit boards, floppy drives, printers, 
       cables and physical pieces of a system. Software is the 
       electronic instructions necessary to make the computer perform. 
       These instructions are usually stored inside a piece of hardware 
       (e.g., software instructions stored inside a circuit chip or 
       floppy drive) but they are nevertheless software. There are two 
       major types of software: operating system software and 
       applications software. 

       Operating system software (like DOS) performs very elemental 
       housekeeping instructions (e.g., where is monitor, how can I 
       keep track of what data is on which track or sector of a floppy 
       drive.) 

       Applications programs perform tasks on a higher level (e.g., 
       word processing programs or database programs are applications.) 
       Generally an application software package uses the lower level 
       operating system (DOS) to do routine tasks (e.g., your word 
       processing application uses the lower level DOS operating system 
       frequently to write and store data on a disk. 

       We interrupt this tutorial for a brief reminder: be sure to
       submit your registration fee to receive your BONUS DISKS!
       Now back to our regularly scheduled tutorial . . .
       
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         INTRODUCTION TO COMPUTER TECHNOLOGY - PROCESSING AND THE CPU 

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       You can pause for a while if you like or go onto to another 
       tutorial. But if you want delve into great complexity, read on.

       Now it's time to delve deeper into the heart of the computer. 
       The central processing unit or CPU is the "brains" of every 
       computer. On the PC, the CPU is simply a tiny integrated 
       circuit. It is the control center and contains two circuit 
       elements to perform tasks plus several special locations or 
       memory areas called registers which hold instructions. 

       Registers, located within the CPU chip are temporary storage 
       locations which hold instructions. Secondly, the arithmetic 
       logic unit or ALU is the location within the CPU where seven 
       basic math and logic operations take place (such as addition and 
       subtraction.) Finally, the control unit is a portion of the CPU 
       which directs all elements of the computer. It does not add or 
       subtract like the ALU, it only directs the activity. 

       Let's first examine the registers within the CPU. Four registers 
       are present in the CPU - some computers contain more than four. 
       The storage register is simply a parking area for information 
       taken from or sent to memory. The accumulator register 
       accumulate the results of calculations. The address register 
       stores the location of where the information or instructions are 
       located. Finally, one or more general purpose registers are 
       usually available and have several functions which can 
       interchangeably include addressing (where is it?) or arithmetic 
       (add or subtract it.) 

       Registers can vary in size or bits with the variety of the 
       computer. 8-bit registers are common on small computers. 16-bits 
       for larger personal computers. And finally minis, mainframes and 
       supercomputers have 64-bit or larger registers. This length (8-
       bit, 16-bit, etc) is called a word and frequently larger and 
       more powerful computers feature larger register size. 

       Despite this seeming complexity a basic fact remains: all 
       digital computers can only add and subtract two numbers: zero 
       and one! Let's back up a bit. For purposes of digital computer 
       electronics, internally a computer can only respond to two 
       things: on and off - just like a light switch. These electronic 
       states of being might actually be a positive and negative 
       voltage or a high and low voltage stored in a series of 
       transistors etched in silicon on a chip, but to the computer the 
       logic is on or off. Two conditions, that is all. 

       Back in the human world we can represent these as one and zero 
       (1 and 0). A special branch of mathematics deals with 
       calculations of numbers represented by 1 and 0 which is called 
       binary arithmetic. 

       Each one or zero is a pulse of electricity or magnetism 
       (electricity inside a chip, magnetism out on the surface of a 
       floppy disk.) Each pulse, either a 1 or 0 is called a bit. Whole 
       series of bits in a row can be used to represent numbers larger 
       than 9 in our human decimal system. Bits in strings of eight 
       units are called bytes. One byte represents a single character 
       of data in the computer. As a curious aside, a nibble is half a 
       byte or four bits. 

       We go back to our analogy of the light switch (on and off 
       representing one and zero to a computer.) In simplest terms, if 
       we have two light switches we have the following ideas: 

       OFF OFF = 0 0 = (human decimal number) zero   = 0 
       OFF ON  = 0 1 = (human decimal number) one    = 1 
       ON  OFF = 1 0 = (human decimal number) two    = 2 
       ON  ON  = 1 1 = (human decimal number) three  = 3 

       Notice something peculiar: in the above we find FOUR binary 
       numbers (0,1,2,3) but THREE human decimal numbers (1,2,3.) We 
       rarely think of 0 as a number since we consider it NOTHING.) To 
       computers ZERO is always a number!!! 

       Going a little further a single bit can only represent two 
       numbers: (ON or OFF = 1 or 0 ). Two bits (our above example can 
       represent four numbers (0,1,2,3). And four bits could represent 
       16 numbers. If you go all the way to a byte (eight bits) you 
       could get 256 numbers. The pattern is that each additional bit 
       doubles the quantity of possible numbers. 

       To a computer these binary numbers march together in a long 
       string, one after another. Remember, the CPU has only two 
       numbers to work with: 1 and 0. 

                             Human   Computer 
                           Decimals   Binary                   
                                0  -      0                                  
                                1  -      1                                  
                                2  -     10                                  
                                3  -     11                                  
                                4  -    100                                  
                                5  -    101                                  
                                6  -    110                                  
                                7  -    111                                  
                                8  -   1000                                  
                                9  -   1001                                  
                               10  -   1010                                 
                               11  -   1011                                  
                               12  -   1100                                  
                               13  -   1101                                  
                               14  -   1110                                  
                               15  -   1111                                  

       Notice several eccentricities about this system. In binary, 
       start on the right and keep adding digits to the left. When you 
       fill a space with all 1's, you zero out everything, add one 
       digit to the left, and start with "1" again. When you reach 
       binary 111 you start the WHOLE series over again with a 1 in 
       front of it. One bit counts two numbers, two bits count four, 
       three bits count eight and so on as we mentioned earlier. When 
       you add a binary digit to the growing string of 1's and 0's you 
       double the number of total decimal digits you can use! 

       These eccentricities appear odd, but to the computer they are 
       shortcuts which simplify calculations and keep things to 1's and 
       0's. It is this simple system of on and off (like light 
       switches) which make computers and their odd binary system so 
       FAST! 

       Now that we understand the basic binary arithmetic of a computer 
       we can say a few words about addressing. Simply put, each piece 
       of information in the computer lives in a little memory location 
       (like eggs in a carton -each egg is a piece of data, each carton 
       hole is an address or location.) Each address is unique, of 
       course. The first address, the second, and so on. How many 
       addresses can an 8-bit binary number describe? 256. A 16-bit 
       number can specify 65536 addresses or possible locations for 
       data. 

       As we finish our introduction to computer technology we should 
       briefly list a few terms. There are more in the glossary 
       contained elsewhere on this disk.

       Kilo - Thousand units. Example: kilobyte. Because of the binary 
       math associated, this is actually 1024 bytes. Frequently 
       abbreviated as the simple letter "K". 

       Meg -  Million. Example: 20 Meg hard disk which hold 20 million 
       bytes approximately. 

       Millisecond - One thousandth  of a second. 

       Microsecond - One millionth of a second.                               

       Nanosecond - One billionth of a second.                              

       Picosecond - One trillionth of a second. 

       Tutorial finished. Be sure to order your FOUR BONUS DISKS which 
       expand this software package with vital tools, updates and 
       additional tutorial material for laptop users! Send $20.00 to 
       Seattle Scientific Photography, Department LAP, PO Box 1506, 
       Mercer Island, WA 98040. Bonus disks shipped promptly! Some 
       portions of this software package use sections from the larger 
       PC-Learn tutorial system which you will also receive with your 
       order. Modifications, custom program versions, site and LAN 
       licenses of this package for business or corporate use are 
       possible, contact the author. This software is shareware - an 
       honor system which means TRY BEFORE YOU BUY. Press escape key to 
       return to menu. 
       

