Computers
as a Second LanguageComputers
as a Second LanguageComputer Fundamentals
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NEAT STUFF ABOUT BITS AND BYTES  How
many 8-bit panels or bytes were there in a standard IBM or
IBM-compatible computer in 1980? Take a guess. Ten thousand panels,
twenty thousand panels, one hundred thousand panels? The answer is
640,000 8-bit panels or 640,000 bytes. This is usually written as 640 KB
meaning 640 kilobytes (kilo means thousand). The total number of bytes
is commonly referred to as the computer's memory capacity.
And remember, each of these 640,000 bytes can hold any of 256 possible
conditions representing numbers from 0 to 255. Awesome!So
far we have discussed how the computer holds numbers but we have not
mentioned letters of the alphabet. Obviously if a computer can do word
processing it must understand the alphabet, right? Wrong! Computers have
no idea what the alphabet is. Remember, the only thing a
computer understands is whether switches are off or on.
Every letter of the alphabet and every punctuation mark is represented
by a numerical value which is held in a single byte. The uppercase
letter "A" has a numerical value of 65 and the lowercase
letter "a" has a numerical value of 97. A comma (,) is number
44, a colon (:) is number 58. Even a blank space ( ) has a number, 32.
So how does the computer know that a byte containing the value 65 is the
letter "A" and not the number 65? Once again it is the CPU or "brain"
that keeps track of every byte and knows which is which.A
old computer with a memory capacity of 640 kilobytes is surprizingly
versatile. It can be used for word processing, accounting, filing,
games, etc. In order to perform any of these functions, you must provide
the computer's memory with an appropriate set of instructions to follow.
These instructions, commonly called software, are
usually loaded into the computer's memory from a disk. If you type a
business letter with word processing software, everything you type also
goes into the computer's memory. If you turn the power to the computer
off, everything you have typed as well as the word processing software
will disappear from the computer's memory. The only way to get the
instructions back into the computer is to turn the computer on and load
the instructions from disk again. The name for this computer memory is
RAM, which means Random Access
Memory. Since the CPU can access any portion of this
memory as it is needed, the term Random Access Memory is appropriate.Earlier
we mentioned that the CPU, or brain, of the computer is pre-programmed
at the factory to know everything that is going on in the computer's
memory. In addition to the CPU, there is a whole series of instructions
pre-programmed at the factory called the Operating
System or OS. This portion of the
Operating System contains essential instructions which do
not disappear when the computer is turned off. You can
think of the Operating System as a bunch of switches which have been
permanently set with crazy glue! These instructions are responsible for
making the computer operate properly from the moment you turn it on.
Since these instructions never disappear and never change they are
called ROM or Read Only
Memory.To
summarize, we have learned that computers operate with thousands of tiny
switches that can be either off or on. The ROM contains switches which
have been permanently set at the factory to control how the computer
operates. The RAM contains switches which are all turned off when the
power to the computer is turned off. The RAM switches are activated by
whatever we choose to use the computer for. If we load a word processing
program from disk the RAM switches will be set according to how they
were stored on the disk. If we type a letter, additional RAM switches
will be set according to whatever we decide to type. If we load a
computer game, the RAM switches will be set according to how they were
stored on the game disk and give us another unique use for the computer.
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