Applications (word processors, video games, etc.) are sets of instructions.

CPU

The CPU (Central Processing Unit) is a big, green,

plastic board with a lot of chips and many other

electronic components mounted on it.

The central processing unit is also called "the

processor". It is the "brain" of the computer; it looks

at the information and takes decisions based on

logic.

RAM (Random Access Memory): This is a green

plastic card with chips.

The RAM is installed in a slot on the mother board.

Mother boards have empty slots so that we can add

more RAM if we want.

The RAM stores the applications and files that we are

using.

Hard disc: Also called "hard drive", it is a set of rigid discs

with a magnetic surface.

It stores all your programs and files.

The Operating System (OS)

There is one OS per computer; nat more, not less.

The OS defines the internal logic for the functioning of the computer.

To program the OS, we must know which are the components of the hardware and how

they are connected.

For example, when we tell the computer to switch off, the OS decides to first close the

applications, then to transfer all data from the RAM to the HD, and finally to switch itself off.

Operating systems evolve along with computers. In the 1980s only one user could interact

with a computer and computers only had text, not images.

Computers had one processor, one application, one floppy disc, one keyboard and

screen.

The OS was programmed only to manage those hardware components.

one

In those days, the 0S was stored on a floppy disk, which was loaded after switching on the

computer.

The user first loaded the OS, (stored on an external disk) and then the application (stored on

another external disk). The user could then start to use the application.

Today's OS

It is stored in the hard disc (the applications are also stored in the HD).

It can manage multiple applications at the same time.

It has a graphic display, so we can interact with the computer using a mouse.

It can connect to the internet.

Today, the most common operating systems are those sold by

Microsoft: Windows Vista, Windows 7..

Microsoft's Windows has a long history which started with the OS

called "DOS" (Disc Operating System).

Apple Macintosh is another company which offers an OS for

computers. The "Mac" is preferred by graphic designers and artists.

LINUX is a free OS. "Free" means that users don't have to pay to

use it, and that programmers can modify the O5 as they like.

There are also various OS for mobile telephones.