用英文介绍一种高科技产品如计算机

Computer
A general-purpose machine that processes data according to a set of instructions that are stored internally either temporarily or permanently. The computer and all equipment attached to it are called hardware. The instructions that tell it what to do are called "software." A set of instructions that perform a particular task is called a "program" or "software program."

What a Computer Does
The instructions in the program direct the computer to input, process and output as follows:

Input/Output
The computer can selectively retrieve data into its main memory (RAM) from any peripheral device (terminal, disk, tape, etc.) connected to it. After processing the data internally, the computer can send a copy of the results from its memory out to any peripheral device. The more memory it has, the more programs and data it can work with at the same time.

Storage

By outputting data onto a magnetic disk or tape, the computer is able to store data permanently and retrieve it when required. A system's size is based on how much disk storage it has. The more disk, the more data are immediately available.

Processing (The 3 C's)
The computer performs all processing by "calculating," "comparing" and "copying" the data stored in its memory (RAM).

Calculate

The computer can perform any mathematical operation on data by adding, subtracting, multiplying and dividing one set with another.

Compare

The computer can analyze and evaluate data by matching it with sets of known data that are included in the program or called in from storage.

Copy

The computer can move data around to create any kind of report or listing in any order.

Calculate, Compare and Copy

By calculating, comparing and copying, the computer accomplishes all forms of data processing. For example, records are sorted into a new order by comparing two records at a time and copying the record with the lower value in front of the one with the higher value.

The computer finds one customer out of thousands by comparing the requested account number to each record in the file. The query statement: SUM SALARY FOR TITLE = "NURSE" causes the computer to compare the title field in each record for NURSE and then add (calculate) the salary field for each match.

In word processing, inserting and deleting text is accomplished by copying characters from one place to another.