HP 3000 Manuals HP 3000 Manuals
The Idea Behind Computing
In some ways, the operation of a computer mimics the kind of thinking
that you do every day. When you set out to solve a problem or accomplish
a task, you are likely to have a method, a way of doing things, that
works for you. Many of your methods are so automatic that you do not
think about them. Many of the computer's methods seem automatic;
however, everything that the computer does--from the simplest to the most
complex task--is controlled by strict and specific instructions
(programs).
If you have ever written down a list of numbers and added them up, you
have used procedures--input, processing, and output--that parallel the
operation of a computer.
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|A problem in arithmetic |
| |
| 234 What is your method for adding |
| 19 these numbers? Do you first |
| 8 add all the numbers in the right |
| 611 column, or do you add 234 to 19 |
| ---- and then add 8 to that sum, and |
| 872 so on...? |
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Any method that consistently yields the correct solution is a good one.
Where the numbers come from, what you do with them, and where the results
go are important--to you and to the computer.
* The numbers come from somewhere. Perhaps they come from the
records of your monthly spending.
For the computer, information that comes from somewhere is called
input.
* You do something with the numbers: you add them to produce a sum.
The sum did not exist until you performed the addition.
Using existing information to produce new information (or to
change the content or nature of existing information) is called
processing.
* The result (the sum) you obtain goes somewhere. You might add it
to the records of your yearly spending.
Sending (or saving or storing) information somewhere is called
output.
Your mental computer
Over and over again throughout this process of adding numbers, you are
taking in information, recording information, moving information from one
place to another, and manipulating existing information to produce new
information.
In our day-to-day lives, we use input and output so automatically that we
have to stop and think before we realize exactly how much input and
output is occurring.
We you see a number written on a piece of paper, the image of the number
enters your mind. That is input. If you then turn around and write that
number on another piece of paper, you move the image in your mind onto
the paper. That is output.
It does stretch the imagination, but what the paper "receives" when you
write down a number is input for the paper.
If you write down a series of numbers on the paper and then perform
addition, you are engaged in a startling number of input-output
exchanges.
Somewhere between taking two numbers into your mind and writing down
their sum, the mental steps required to perform addition come into play.
In these steps, your mind does what the system processing unit of a
computer would do: joins two (or more) numbers to create a third number.
This is processing.
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|Input and output are so closely associated in the operation of |
|computers that they are almost considered a single process: |
|Input/Output, sometimes abbreviated as I/O. |
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Because the sum is important in your budget, you "output" it once again,
perhaps to an accounting ledger, and record it for future use. Having
recorded this important information, you are free to turn to other tasks,
assured that you can retrieve the information when you need it. The
computer, too, records information (in files--in its own memory, on
disks, or on tape) for later retrieval.
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|For the computer, "forgetting" something happens when you turn off the|
|power or erase a file from a disk or a tape. |
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So a computer is....
You can think of a computer as the sum of all of its pieces of hardware.
If you include all of its software in that definition, you are closer to
the truth. And if you go no further, you have an entirely workable
definition.
Here you are invited to consider the computer, too, as the sum of the
processes (actions) that it performs.
Considered as the sum of its processes, a computer truly is whatever the
computer is doing when you use it. This may sound strange. But consider
what a carpenter is. A carpenter is someone who....Now, list all the
things that a carpenter does. The list could be very long.
The carpenter may also be a parent, a loving spouse, an avid
photographer, an active participant in community affairs. The human
being who is all of these things is doubtless a very complex individual.
Yet, when you hire the carpenter to build something, you hire the
knowledge, skills, and activities that make the person a carpenter. In
that sense, a carpenter is what a carpenter does. In that sense--in a
very restricted sense--a carpenter is a "process."
In a similar fashion, the computer follows command or program
instructions in order to take on the role of report writer, document
printer, accountant, record keeper, assembly line coordinator, product
designer, mail deliverer....The list goes on and on.
In its simplest activities, a computer takes and records information.
When necessary, it "remembers" what it recorded. When instructed to act,
it applies appropriate rules (found in programs) to the information it
has and displays or records the results. When necessary, it moves
information from one place to another.
The information might be numbers, or letters of the alphabet, or words,
or illustrations, or some combination of them. Some computers even work
with sounds.
What is your computer right now? It is what you instruct it to
do--assuming that it is able to carry out your instruction.
What computers do
* take information from somewhere (input)
* transfer information somewhere else (output)
* display information (output)
* record information (output)
* recall (remember) information
* follow rules (programs or commands)
* carry out instructions (programs or commands)
* manipulate information to produce new results (processing)
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