CPU:

The CPU (Central Processing Unit) is a big, board with a lot of chips, the central processing unit is also called "the processor". It's the "brain" of the computer; it looks at the information and takes decisions.

Memory:

Memory stores information, they normally stay inside the computer. There are 2 types of memories and portable memories.

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

with a magnetic surface. It stores all your programs and files.

Advantages:

It can store a large amount of data.

We can save and erase the information when we want.

Disadvantages: It's slow compared to other types of memory, it takes longer.

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 use.

Advantages: It stores and retrieves quickly.

Disadvantages: You lose the work if there is an electrical power cut. Small memory capacity compared to the hard disk.

Portable memories:

They are easy to connect and disconnect from the computer and they are easy to carry.

CDs, DVDs: We call them "optical memories" because they use light to work.

Advantages:

They are cheap compared to the other ones.

Disadvantages:

They are not good to rewrite.

Pen drives and memory cards store the information

in chips.

Advantages:

Rewritable and quick.

Disadvantages:

They are more expensive than a CD's and DVD's.

Graphics card:

The graphics card looks similar to the RAM. It's a green plastic with card and chips.

It defines the format of the graphics and helps the processor to process the graphics faster.

We need a powerful graphics cards to play video games, to watch movies and for graphic design.

Peripherals:

Peripherals are elements of communication between the computer and the outside world(including ourselves).

Operating System(OS):

There is one OS per computer.

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 turn 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 disc, one keyboard and one screen. The OS was programmed only to manage those hardware components.

In those days, the OS was stored on a floppy disk, which was loaded after turning on the computer. The user first loaded the OS, and then the application. The user could then start to use the application.

Today's OS:

It's stored in the hard disc. 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".

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 OS as they like.

There are also various OS for mobile telephones.