COMPUTERS AND PROGRAMS:
In this chapter you are going to find out what a computer is and get an understanding of
the way that a computer program tells the computer what to do. You will discover what
you should do when starting to write a program, to ensure that you achieve a “happy
ending” for you and your customer. Finally you will take a look at programming in
general and the C# language in particular.
what is computer:
One way of describing a computer is as an electric box which hums. This, while
technically correct, can lead to significant amounts of confusion, particularly
amongst those who then try to program a fridge. A better way is to describe it as:
A device which processes information according to
instructions it has been given.
This general definition rules out fridges but is not exhaustive. However for our
purposes it will do. The instructions you give to the computer are often called a
program. The business of using a computer is often called programming. This is not
what most people do with computers. Most people do not write programs. They use
programs written by other people. We must therefore make a distinction between users
and programmers. A user has a job which he or she finds easier to do on a computer
running the appropriate program. A programmer has a masochistic desire to tinker with
the innards of the machine. One of the golden rules is that you never write your own
program if there is already one available, i.e. a keen desire to process words with a
computer should not result in you writing a word processor!
However, because you will often want to do things with computers which have not
been done before, and further because there are people willing to pay you to do it, we
are going to learn how to program as well as use a computer.
HARDWARE AND SOFTWARE:
If you ever buy a computer you are not just getting a box which hums. The box, to be
useful, must also have sufficient built-in intelligence to understand simple commands
to do things. At this point we must dra w a distinction between the software of a
computer system and the hardware.
Hardware is the physical side of the system. Essentially if you can kick it, and it stops
working when immersed in a bucket of water, it is hardware. Hardware is the
impressive pile of lights and switches in the corner that the salesman sold you.
Software is what makes the machine tick. If a computer has a soul it keeps it in its
software. Software uses the physical ability of the hardware, which can run programs,
to do something useful. It is called software because it has no physical existence and it
is comparatively easy to change. Software is the voice which says "Computer
Running" in a Star Trek film.
All computers are sold with some software. Without it they would just be a novel
and highly expensive heating system. The software which comes with a computer is
often called its Operating System. The Operating System makes the machine usable.
It looks after all the information held on the computer and provides lots of
commands to allow you to manage things. It also lets you run programs, ones you
have written and ones from other people. You will have to learn to talk to an
operating system so that you can create your C# programs and get them to go.
DATA:
People use the words data and information interchangeably. They seem to think that
one means the other. I regard data and information as two different things:
Data is the collection of ons and offs which computers store and manipulate.
Information is the interpretation of the data by people to mean something. Strictly
speaking computers process data, humans work on information. An example, the
computer could hold the following bit pattern in memory somewhere:
11111111 11111111 11111111 00000000
You could regard this as meaning:
"you are 256 pounds overdrawn at the bank"
or
"you are 256 feet below the surface of the ground"
or
"eight of the thirty two light switches are off"
The transition from data to information is usually made when the human reads the
output. So why am I being so pedantic? Because it is vital to remember that a computer
does not "know" what the data it is processing actually means. As far as the computer
is concerned data is just patterns of bits, it is the user who gives meaning to these
patterns. Remember this when you get a bank statement which says that you have
£8,388,608 in your account!
PROGRAMMING:
Programming is a black art. It is the kind of thing that you grudgingly admit to doing
at night with the blinds drawn and nobody watching. Tell people that you program
computers and you will get one of the following responses:
1. A blank stare.
2. "That's interesting", followed by a long description of the double glazing that
they have just had fitted.
3. Asked to solve every computer problem that they have ever had, and ever will
have.
4. A look which indicates that you can't be a very good one as they all drive
Ferraris and tap into the Bank of England at will.
Programming is defined by most people as earning huge sums of money doing
something which nobody can understand.
Programming is defined by me as deriving and expressing a solution to a given
problem in a form which a computer system can understand and execute.
One or two things fall out of this definition:
You need to be able to solve the problem yourself before you can write a
program to do it.
The computer has to be made to understand what you are trying to tell it to do.
PROGRAMMER:
I like to think of a programmer as a bit like a plumber! A plumber will arrive at a job
with a big bag of tools and spare parts. Having looked at it for a while, tut tutting, he
will open his bag and produce various tools and parts, fit them all together and solve
your problem. Programming is just like this. You are given a problem to solve. You
have at your disposal a big bag of tricks, in this case a programming language. You
look at the problem for a while and work out how to solve it and then fit the bits of
the language together to solve the problem you have got. The art of programming is
knowing which bits you need to take out of your bag of tricks to solve each part of
the problem.
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