Unit 2 Designing a Computer System

Date: 2015-10-07; view: 417.

Paul bailey: Yes, well I'm not a computer expert. Could you please explain what this char means?

computer consultant: Yes, of course. A computer system consists of hardware and software. Hardware means the different types of equipment or devices, and software means the programs. OK so far?

PAUL BAILEY: Yes.

computer consultant: Anyway, hardware comprises 2 components — the central processing unit and the peripheral equipment. The central processing unit or CPU is the brain of the computer. It controls all the equipment and processes information — just like your brain controls your body and also makes decisions. The other component, peripheral equipment, we use for 3 purposes — firstly to give information to the computer as input; secondly to store information for the future; and thirdly to get information from the computer as output. So we can split peripheral equipment into input, storage and output. Now let's take the payroll as an example. What do you war to get out of the computer?

paul bailey The wages of my employees.

computer consultant: Uh-huh. So that's your output. Now in what form do you want this information to appear?

paul bailey: On paper.

computer consultant: Right. So on your diagram under output we've got a printer. A printer is one kind of output device and of course it prints information. Also on your diagram is another type of output device — a visual display unit or VDU. Now a VDU is a kind of screen. Often you don't want to print everything — you just want to see what's what. So we can classify a printer and a VDU as peripheral output equipment. OK so far?

PAUL BAILEY: Yes.

computer consultant: OK. Let's go on a bit further, but let's stay with the payroll. What kind of information do you need in order to calculate the payroll?

paul bailey: Employee's name, hours worked, hourly rate, overtime worked, overtime rate, and tax code. And then I need a calculator and tax tables.

computer consultant: Well, this brings us back to the other 2 categories of peripheral equipment — input and storage. But let's consider storage first. A store is like a file. A present your files consist of sheets of paper or card. With a computer system your storage devices fall into 2 categories. You'll see them on your diagram under storage -tape and disk. They can contain information about employees just like a file, and they operate like a tape recorder or record player. You can put information on and record it and you can get that information back at a later time — and of course you can change the information very easily. And finally let's consider your input device. The simplest and most common type of input device is a keyboard. It consists of a typewriter keyboard connected to the other parts of the system. For your payroll calculation you load your employee file from a tape or disk machine. Then the computer will find your first employee and show you his details on the VDU. Then it will ask you to input the details of hours worked, etc. And finally it will calculate his or her wage and print it onto the printer. The only thing we haven't mentioned is software. Software means

programs, and a program consists of a set of instructions which tell the computer how to process the information. For a payroll calculation the program tells the computer what to multiply, what to add, what to subtract, etc. — in fact how to do the whole calculation. And when you are not using a program, it is stored on tape or disk — just like your files.

paul bailey: OK. Enough theory for the moment. When can I see one of these wonderful systems?

computer consultant: I'm glad you asked me that because by chance I've got a beautiful little computer in the back of my car. I'll just go and gt it.