HP 3000 Manuals HP 3000 Manuals
Lesson 1 Computer Hardware
Lesson 1 presents the physical parts of the computer.
* the computer hardware
* the computer peripherals
* the system console
Computers consist of hardware and software components:
Hardware The physical equipment: integrated circuit boards,
disk drives, terminals (the screen and keyboard
together), tape drives, printers, and plotters.
Software The programs that instruct the hardware to do
something (Lesson 2).
Hardware
Hardware is all of the electronic equipment that a computer includes. If
you can touch it, pick it up, or move it around, it is hardware.
A computer consists of a central unit, called the central processing unit
(CPU), and external devices, called peripherals.
CPU The central processing unit is the "brain" of the
computer. Every instruction given to the computer
passes through the electronic circuits of the CPU.
When you program the computer to add two numbers
together, the arithmetic is performed in the CPU.
When you want something sorted, the CPU controls
the task from start to finish.
SPU The system processing unit contains all of the
components of the computer system including the
central processing unit. The SPU does not refer to
the system console or any other single, peripheral
device.
Peripherals Peripherals are all of the other hardware connected
to the CPU. Peripherals are often referred to as
peripheral devices.
The computer assigns to each device an identifying
number called an LDEV number. This number is the
"address" (of your terminal, for instance) that the
computer uses when it sends and receives
information.
Peripherals
There are five classes of peripherals that may be connected to a standard
HP 3000 system:
Terminals Your terminal (the screen and keyboard) gives you a
way of communicating with the computer. You can
enter commands or run programs and see the results.
Disk Drives Information and programs that are not being used by
the SPU are stored on disk drives. The information
could be the text of a letter, information in a
database, or a program that you might use every
day.
There might be one or many disk drives attached to
your computer.
Information on a disk drive can be retrieved
quickly.
Tape Drives Information that is not accessed frequently but
must be kept for a long time is stored on magnetic
tapes. Tape drives are used to store information
from the disk onto the tape.
The computer takes longer to retrieve information
from a tape. The advantage of tape lies in safely
keeping backup copies of vital information or
programs. If information is ever lost from the
computer, it can be restored to the system from the
tape(s); however, the restored version of a file
might not be the most up-to-date version of the
file. It might be an earlier version.
It is common practice for system operators to store
all of the disk files on the computer to back up
tapes at regular intervals. Thus, if you lose or
accidentally erase an important file, there is a
reasonable chance of having that file restored to
the computer.
Printers Printers come in all shapes and sizes. Some are
designed for extremely high speeds. Some are
designed for very high-quality, finished documents.
There may be one or many printers attached to your
computer. If there is only one, it may be referred
to as the line printer.
System Console The system console is a special terminal that your
system operator uses almost exclusively to control
the day-to-day functioning of the computer. The
system console is usually located close to the CPU.
Figure 2-1 shows a typical computer system.
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Figure 2-1. A Typical Computer System