Lesson 1 Computer Hardware

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.

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 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.

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.

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.

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 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.

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.