Computers
as a Second LanguageComputers
as a Second LanguageComputer Fundamentals
HOW
DO COMPUTERS WORK? Computers
contain thousands of tiny electrical switches located in microchips. As
expected, each switch can be either off or on. The various combinations
of which switches are off and which are on dictate what the computer is
doing at any given moment. You can imagine with thousands of switches
operating there is virtually an infinite number of combinations of
"offs" and "ons".
This explains why computers can function in so many different ways -
from a game machine to a word processor!If
you think of a single light switch, there are only two distinct
conditions which are possible, off or on. What happens if there are two
switches controlling two separate lights? We'll call the lights "A"
and "B". Now there are four distinct conditions which are
possible as listed below:·
condition 0) both lights off· condition 1) light "A" on and light "B" off · condition 2) light "A" off and light "B" on · condition 3) both lights on Notice
that our numbering system starts from zero. This is because with both
lights off there is no current flowing to either light so we call it
condition 0.Look
around your home and see if you can find a triplet panel,
3 switches grouped together to control three separate lights ("A",
"B", and "C"). Can you guess how many distinct
conditions are possible with three switches at your disposal? The answer
is eight conditions. As discussed before, we start the numbering from
zero:·
condition 0) all three lights off· condition 1) light "A" on, light "B" off and light "C" off · condition 2) light "A" off, light "B" on and light "C" off · condition 3) light "A" on, light "B" on and light "C" off · condition 4) light "A" off, light "B" off and light "C" on · condition 5) light "A" on, light "B" off and light "C" on · condition 6) light "A" off, light "B" on and light "C" on · condition 7) all three lights on Why
did your home builder group these light switches together as a triplet
panel? The answer is efficiency and convenience. It's much easier to
control all three lights from one position in the room than it would be
to move all around from wall to wall to control each light. Computer
designers also found it much more efficient to group computer switches
together into panels. The most common grouping is eight
switches on each panel. Would you care to guess how many
distinct conditions are possible with eight switches at your disposal?
Here's a clue by reviewing what was discussed above:·
with 1 switch there were 2 distinct conditions possible (conditions 0 -
1)· with 2 switches there were 4 distinct conditions possible (conditions 0 - 3) · with 3 switches there were 8 distinct conditions possible (conditions 0 - 7) Do
you see a pattern to this yet?·
with 4 switches there are 16 distinct conditions possible (conditions 0
- 15)· with 5 switches there are 32 distinct conditions possible (conditions 0 - 31) · with 6 switches there are 64 distinct conditions possible (conditions 0 - 63) · with 7 switches there are 128 distinct conditions possible (conditions 0 - 127) · with 8 switches there are 256 distinct conditions possible (conditions 0 - 255) It
seems incredible but it is true. With 8 switches grouped together on one
panel, there are 256 unique and distinct conditions that can be
controlled from this panel! In computer terminology, each switch on the
panel is called a bit. The full group of 8 switches is
called a byte.A
byte can represent any number from 0 to 255. We all know that computers
deal with numbers bigger than 255. If a number is bigger than 255, the
computer requires yet another byte to make the number. For example, the
number 256 would take up 2 bytes - the first one would hold the maximum
amount of 255 and the second one would hold the amount of 1. The sum of
255 + 1 is therefore 256. Let's try another example. How many bytes
would the computer need to hold the number 65025? Did you guess 255
bytes? Incorrect! The computer only requires 2 bytes to hold the number
65025! This time the computer multiplies the value of 255 in the first
byte by 255 in the second byte to give the value of 65025. To hold a
bigger number, like 67000, the computer would require yet another byte
for a total of 3 bytes.How
does the computer know that it should multiply the 2 bytes to create the
number 65025 and add 2 bytes to create a number like 256? This is the
responsibility of the computer's Central Processing
Unit (CPU) or the brain
of the computer. The CPU is contained on a tiny microprocessor (about
1/4-inch square) and is programmed at the factory to be able to look at
any of the 8-bit panels (or bytes) and figure out what it is to do with
them. |
