第4课
人机信息交换与存储
课文
Information Exchange and Store
1. Data must be entered into the computer. Then the computer can process them to
some results. After that, the computer must let the user know the results. And, the
data or the results must be kept if they are useful. So there are the problems: How
to exchange information between the user and the computer? And how to store the
information?
2. The user can give the data or commands to a computer by input devices, get the
information from the computer by output devices, and store the useful parts by
storage devices.
3. The most common used input devices: keyboard and mouse.

The keyboard is used for entering. It is very important to learn how to use
it correctly and efficiently. The standard keyboard, looks like the typewriter
keyboard, is divided into four sections: the typewriter keyboard, the function
keys, the directional keys (arrow keys, special-purpose keys etc), and the
numeric keypad.

The mouse is used to control the pointer on the display screen. It is a pointing
device. Most of them have two buttons. The right-handers use the left button
for most operations and the left-handers use the right button to do the same
work. Move the mouse on the flat and the pointer move with it on the screen.
Depress the button after the pointer point to the icon. And the computer will
perform the task you want.
4. The most common used output devices: monitor and printer.

The monitor is also called video display screen. It is used to display text
or images on the screen. Most people use a color monitor today. A color monitor
can display thousands of colors. And there are many factors of a monitor such
as screen size, resolution etc.

The printer is used to get a hard copy. There are three most popular types of
printers. They are laser printers, ink jet printers, and dot matrix printers.

The laser printer produces high-quality output. But they are expensive.

The ink jet printer makes high-quality output and it is less expensive.
But it is slow.

The dot matrix printer has been widely used for a long time. Although it
works slowly, the quality is not good enough, and the noise is annoying,
but it is inexpensive.
5. People use input devices and output devices to exchange information with the
computer. And there must be something they want to keep for next access. Secondary
storage is used for this purpose. People did a lot to keep information safely,
permanently, read them back easily, and take them around conveniently. There are
two types of technology: magnetic technology and laser technology. Floppy disks,
hard disks and magnetic tapes use magnetic technology. Optical storage devices such
as CD-ROM use laser technology.
6. With the help of these peripheral devices above (input/output devices and
secondary storage), people can exchange information with the computer. And there
are other devices such as scanners, light pen etc.