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--HOW TO --
BASIC BACKGROUND PRINCIPLES
PAGE 1 OF 4
A typical "PC" "IBM" computer is Binary, and Electrical. Every wire in the computer's chips, is either "ON" or "OFF", which is + 5 Volts, or Zero Volts. " BI" means two ( as in two wheeled "Bi-cycle" ) and there are only two states, "on" or "off". Thus, any wire or transistor in the computer is in one of TWO (2) possible "states".
The old CPU chip above has 4.5 MILLION transistor switches. New Central Processor Units have HUNDREDS of millions !
If you turn on an ordinary wall light switch, the switch is either "on" or "off". The computer is exactly the same. The biggest number that a computer wire or transistor can count to, is " ONE ". If the wire is "on" and has + 5 volts, the number is " one ". If the wire or transistor is " off ", and has zero volts of electricity, then the binary number is "zero". That is all ANY part of a computer can do - count from zero to one.
Kids will often ask, at this point " If a computer can only count from zero to one, why are computers so powerful?" Ask the student to turn on and off the wall light switch as fast as possible in one second. Then explain that the first, oldest, slowest "PC" chips turn on and off 6 million times in one second! And, that there can be millions of transistors and wires in a single chip, and that there are 50 chips or more in a single computer! This is like having every person in North America turn on and off light switches 6 million times a second - now, it starts to become clear how computers can be so powerful, when the biggest number any part of a computer can count to, is "one ". Note that electricity moves about the speed of light or 186,000 MILES in one second, so that the ZERO'S and ONE'S moving from one switch to another inside the chip, take almost no time at all - VERY, VERY fast !!
I notice that kids, once they realize that a computer can only count to ONE, are immediately "empowered", as they realize that the typical mumbo- jumbo computereeze and "image" often presented of massively complex, super-human computers is really Hollywood hype. They start programmng, and exploring computers with simple "BASIC" language, and start to show amazing creativity and insight. This confidence and understanding, STARTING from being able to count from ZERO to ONE, lasts their lifetime. Computers are very, very SIMPLE, - one might demonstrate this by asking, what is more POWERFUL, a huge 50 ton earthmover, or a little kid with a tiny spoon, sitting in the sand? (( did I mention that the little kid can dig a spoonful of sand and carry it one mile away, 5 billion times a second?? That's 5,000,000,000 times a second )) If you think of the spoon of sand as a DATA " 1 ", and the kid moves the " DATA" at the speed of light, then the tiny spoon is much more powerful than the huge earthmover, -- just like the tiny, simple, "zero and one" math of a computer, can be more powerful than a large building filled with mathematicians using paper and pencils to write down large, complicated, decimal numbers.! !
The second important point to understand, is that the entire computer works on a huge pile, or stack, of "mailboxes", or memory locations, each which has 8 slots in it. The first "PC" type computers shipped with 16 K or 16 thousand memory locations, on chips that were permanently soldered to the main computer board, with no way to add more! Later, and slowly over the years, more memory was added, first in non- upgradeable, permanent, soldered chips, in units like 18 K, and finally, slots for 30 pin memory cards were added so that you could easily add memory chips. Then 32 K, 64 K, 128 K, 256 K, and 512 K computers became available., ( one thousand in computer terms is called " K ", ( Kilo ), so that 512 thousand would be called " Five Twelve K ". ) Random Access Memory ( RAM ) is a stack, starting at the bottom with memory location ZERO. The locations count up, 0 , 1, 2, 3, etc., until the maximum of the computer is reached. The computer can add, subtract, or move each of the 8 zero's or one's in the 8 slots, to other mailboxes or other memory locations.
WHAT IS MEMORY? ? ? ?
After reading this page, an engineering student asked me to better explain what " MEMORY" was and what " RAM " was. From the discussion above, you know that every wire or transistor or capacitor or resistor, which are the building blocks to make an entire computer, can only be in ONE of TWO STATES - "on" or "OFF" or in terms of electricity, + 5 Volts, or 0 (zero) Volts = Binary 1, or 0. The most primitive type of memory, even used today, is simply to connect a group of 8 wires ( 8 bits or binary data units ) to either +5 Volts, or to a "ground" or 0 (zero ) volts. Thus, I can permanently wire one memory location, a group of 8 data values, so that if the computer "looks" at the group, the computer will see a binary value in all 8 locations...
In the demonstration below, a +5 VOLT BATTERY is wired into 8 DATA pins of the PRINTER, PARALLEL PORT on the back of a typical computer's 25 PIN CONNECTOR. If the COMPUTER reads the data on the 8 wires, it would see 01101011. The RED wire from the battery is +5 Volts, and the computer sees any pin conncted to +5 as a DATA "one" ( 1 ), and the GREEN wire from the battery is Ground, or ZERO volts, or "negative", and the computer sees a Zero Volts as a DATA "zero". The wires, from the top of the connector LOOP from pin to pin, in the order, Green, Red, Red, Green, Red, Green, Red, Red. NOTE that the 9 pin and 25 pin Serial, or Mouse, or COMM (Communication) port connectors have pins sticking out, but the 25 pin Parallel, "printer" port connector, just has 25 holes in the plastic. NEW Computers now use ONLY USB connectors, and have NO Serial or Parallel Connectors AT ALL !
When you permanently connect wires to +5 or 0 volts, this is called Read Only Memory, or ROM memory, and once the connections are made at the factory, the data bits are PERMANENT There are hundreds of chips on the market that you can buy, and BURN or zap with electricity, so that locations are permanently shorted out to either (zero) ground or +5 volts. Once you have "loaded" or burned the connections, one at a time on a "programmer", you can put the chip in a computer, and read the program forever, which is often used in tiny computers that run specific devices like scientific instruments, or air conditioning controllers, or calculators, etc.. Even with the power off, the memory locations are permanently burned or shorted together, so there is no problem with starting up the device - the computer always reads the same 0's (zero's) and 1's ( one's) in the same memory locations when you turn ON the +5 Volt power again .
RAM -- Random Access Memory
The typical memory used on a modern computer today is made of millions of tiny CAPACITORS, which temporarily hold tiny amounts of electricity for a millionth or a billionth of a second. Capacitors are very simple ( like most electronics ) and you can make one at home to demonstrate how they work. They are just two metal sheets, with a non-conducting ( insulating) layer of material between them. If you connect the top layer to +5 volts (ex. a battery ), and the bottom to Ground ( zero volts) then the top becomes plus ( + ) and the bottom becomes ( - ) negative as the electrons all collect on one layer, after moving away from the other layer. If you remove the battery, the bottom will still have too many electrons in it, and an electrical meter will show that there's +5 volts, between the two layers of aluminum, even though there is no power connected to the layers-- it is acting like a battery. However, if you connect the top and bottom sheets with a wire, the tiny amount of electricity ( electrons ) that are stored, move through the wire instantly, and dissappear. By using two sheets of aluminum foil, separated by a sheet of plastic wrap or waxed paper, you can make your own capacitor. If you connect the top sheet to +6 volts ( 4 batteries such as 4 AA batteries) and the bottom to the Negative ( zero or Ground), and remove the battery, there will still be +6 Volts between the two sheets. If you connected a meter, it would show +6 volts but only for a fraction of a second, since the electrons will flow through the meter instantly, and dissappear. The voltage on a typical meter will drop immediately to Milli-Volts ( one-thousandths of a volt, ) and the value will count down to ZERO as all the electrons leave. There are expensive voltage meters that do NOT "USE" the electricity that they are trying to measure, but instead just "look at" the charge, and these would clearly show +6 volts for a longer time on the meter, and then slowly drop to ZERO as the "charge", or excess electrons leak away - into the atoms in the plastic , into the table top surface and into the atoms in the air.
A typical large capacitor used in computers is much the same, with two sheets of metal rolled up with a layer of paper soaked in a liquid that insulates ( "electrolyte "), and prevents electricity from sparking across the paper . The bigger the metal sheets, the more "capacitance" and thus, the LONGER the capacitor will "store" the electrons, like a battery.
In a computer, millions and billions of capacitors are made on a grid on the surface of a chip, and these store +5 volts -- however, they are so small that they only save the + 5 volt charge for millionths of a second, and die. The memory has to be read, by the computer, and re-written, every few millionths of a second! Continuously ! There is a special part of one chip on every computer that just reads and writes memory capacitors, over and over, all the time the computer is "on". SO, when you put a 1 ( one ) in a memory location in RAM, on a computer, you are charging a tiny capacitor up to +5 Volts. If the computer needs to look at that memory location later, it will see +5 Volts on "that" capacitor, at "that" memory location. Very simple. The first PC shipped with only 16K of ram or 16,000 memory locations, had NO harddrive, and NO floppy. ( For that matter, it had NO sound card and only a tiny speaker that went " BEEP", it had NO colour monitor - just a green screen,
(The green phosphor was one of the brightest colours available VERY cheaply since it was used on all ocilloscopes and instruments)
The first computers had NO CD or DVD player, it had NO Mouse or pointer of any kind, it had NO USB, NO internet plug, NO 56K modem so that you could not connect to any other computers!) You DID have a second large, "DIN" , round black connection Identical to the keyboard plug on the back, to plug in a connector with 3 wires - sound out, sound in, and on/off to connect to a cassette tape recorder, to store the programs on... Since there were two "keyboard" plugs on the back, rarely labelled, everyone was always plugging the keyboard in the wrong plug... (DIN stands for the Deutsches Institut für Normung, the German National Standards Organization that first named the plug)
At memory location 378 ( in a mathmatical "shorthand" counting system called " HexaDecimal" or "HEX"- see section " MATH " ), there are 8 compartments with either a zero or a one stored in each compartment. These individual one's or zero's, are called " BITS ".
"PC" type computers have a special chip wired to this memory location, which always looks at the 8 bits. If the memory location at 378 has all 8 bits in all 8 compartments filled with zeros, the chip puts Zero Volts on the 8 pins of the Printer Connector on the back of the computer. If you program the computer to put a "one" in the first of the 8 compartments, then the printer port CHIP sees a " one ", or +5 volts on the wire to memory location 378, and puts out + 5 volts, or a "one" on the first pin on the printer connector.
If you program all 8 bits of the memory "mailbox" location 378 to be all " ones ", then the Printer Port Chip will put a " one ", or + 5 volts on all 8 printer connector pins. Very simple. (( NOTE that EVERYTHING on a computer, such as the harddrive, and the floppy work the same way -- at a specific mailbox or group of mailboxes, are chips that INTERFACE or connect the HARDWARE devices, to the memory locations. When the computer wants to use a floppy, for example, it puts a value in a memory location, and the CHIP attached to THAT memory location, turns on the floppy. Very Simple. Another good example is the Green Display of early Computer Monitors. When you wanted a "W" to appear on the screen, you pressed the key on the keyboard, which sent a CODE to the computer. The computer does not know what a " W " is, just that the 3rd key across on the 3rd row down, of the keyboard was pressed. The keyboard generates a code in ZEROs and ONEs ( saying which key was pressed ), and the computer looks at the code pointing to a table of alphabet character ZEROs and ONEs. The computer then copies the Zero's and ONE's in a group of memory locations that are always sent to the MONITOR, so that "W" would be a BINARY group listed below. Every where that there is a "1", the monitor would PRINT a green dot on the screen. Every where that there is a ZERO, there would be a blank.
You can clearly see how a computer, that only knows ZERO and ONE can now print , what appears to humans, as a " W " ! A teacher could put something like (BELOW) on a WHITE BOARD, and ask the class, Is reading
the BINARY CODE for a 286 computer LETTER PRINTING, difficult, or is it easy?
If no one can read the code, ask a student to go to the very BACK of the room, and try to read it!
If you understand that a computer does not know what sound is, what color is, what the alphabet is, or what a mouse or harddrive is then you see how simple a computer is put together - all the computer can do is move ZEROs and ONEs around in its memory. Everything connected to a computer just looks at specific memory locations, for a ZERO or a ONE, which can turn on or off the device, or print a dot on a monitor, or turn on or off a hard drive etc. All the computer " sees " or " knows " is just ZEROs and ONEs Many memory locations have a chip connected to that one location, and a ONE or a ZERO in one of the 8 data bits, will turn on or off a specific computer "hardware" device - for example, the speaker that goes BEEP when you first turn on the computer! The computer does not know there is a speaker that will make a BEEP, all the computer "knows" is that it put a "one" in a memory BIT, in one of the RAM locations. Very simple! (( I call this trait DKDC, " Doesn't Know, Doesn't Care ". If you get many of these Don't Know, Don't Care's piling up, you have a bunch of DKDC's ( pronounced Dee Kay Dee Cee' Z [ DKDC's]) which are then humourously called "DECAY DISEASE" Computers are notorious for doing EXACTLY what they are programmed to do, and unfortunately, many times this is not what you really wanted or intended at all- the computer will blindly move Zeros and Ones around and doesn't know or care what the result is!)) Plus (+)5 volts is enough electricity to turn on an LED (Light Emitting Diode) Light, so that by wiring in 8 LEDs on the printer port's output "DATA" 8 pins, we can " SEE ", the zeros and ones in the memory location 378. Even better, if we wire in small RELAYs ( which can switch on and off higher amounts of power ), we can then turn on and off 8 motors, or lights, or anything we wish.
-----WHAT IS A RELAY?----
A relay starts out as a coil of wire, wrapped around a steel core. Typically there are a thousand or more turns wrapped around the steel center, and these Increase or Amplify the magnetic field of the electricity running through EACH wire so that a thousand turns makes the tiny magnetic force a thousand times stronger - 10 thousand turns of wire would make the magnetic force 10 thousand times stronger, etc. The result is an Electro-Magnet, that turns off and on with the very small amount of electricity used to power it. The magnet, is strong enough to pull down a piece metal which is connected to a SWITCH, and the switch can have hundreds of times more electricity running through it than the electricity in the coil. Thus, a tiny amount of electricity on a DATA line, from a tiny chip, could use a relay to turn on and off a huge, 110 Volt motor!! In my projects, I use inexpensive, easy to find relays, that are not that powerful, and I AMPLIFY the tiny power coming out of the chips with a transistor. I will explain a simple transistor later.
ANIMATED BELOW, you can see the switch work:
Using a simple computer program to put zero's and one's in
memory location 378, we can turn on motors to allow a
solar panel to follow the sun across the sky. We can turn
on and off motors to make toy cars go forward and turn.
We can turn on and off " any " electrical device we wish,
such as lights, heating, refridgerators, water valves, or stereos!
You could wire in controls to run an entire house!
By using simple toys, students can demonstrate Robotic Programming,
with little expense, using "free" computers.
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