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.

Memory stores information. There are various types of memory in the computer: Fixed memories They normally stay inside the computer. 1 . 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 (today around 1 TB). We can save and erase the information when we want. Disadvantages: It is relatively slow: compared to other types of memory, it takes longer to read and write information.

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. Advantages: It stores (writes) and retrieves (reads) quickly. Disadvantages: We lose the work if there is an electrical power cut. Small memory capacity (around 6GB) compared to the hard disk.

They are easy to connect and disconnect from the computer. Also, they are easy to carry. CDs, DVDs: We call them "optical memories" because they use light to work. Advantages: Cheap. Disadvantages: Not good to rewrite. Pen drives, memory cards: They store the information in chips. Advantages: Rewritable. Quick. Disadvantage: More expensive than a CD or a DVD.

The graphics card looks similar to the RAM. It is also a green plastic card with 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.

There is one OS per computer; not 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 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 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.

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 OS as they like. There are also various OS for mobile telephones.

Sometimes we call them "programs", but any piece of software is a program, including the operating system. Applications are programs that we use to do things on the computer; they are our tools. You probably know a lot of them already: Word (word processor), Excel (spreadsheet), Access (database), PowerPoint (presentations), FIFA 11 (game), Messenger (telecommunication software), Autocad (CAD)... An "application suite" is a group of applications in a package. For example: Open Office, Microsoft Office or iWork'09. Application suites normally include a word processor, a spreadsheet, a web browser and other applications. The applications in the suite have a common user interface so that the user can easily learn how to use all of them. The different applications of an application suite can interact with each other. So we can, for example, insert a spreadsheet in a word processor document.

To make a presentation with PowerPoint 2010, follow these steps:

1 When we open PowerPoint a window asks what kind of presentation we want, select "Blank Presentation".

2 Another window offers a selection of layouts; select the default layout.

3 Click on the rectangle that says "Click to add title" and write "Presentation About Mechanisms".

4 Click on "Click to add subtitle" and write "This presentation is about the most common types of mechanisms".

5 Click on "Insert" and then click on "New Slide". The window with a selection of layouts appears again; select the layout called "Bulleted List" (it is normally offered as default) and click on "OK".

6 With the mouse, click on "Click to add title" and write "Types of Mechanisms".

7 Click on "Click to add text" and write: Pulleys Levers Gears

9 We can also insert tables, clip art images, shapes, charts, etc. Insert a table and a chart.

10 To change the colour of the text, select the text with the left mouse button, then select the colour icon and then choose the colour you would like. We can choose the colour before we start to write, so we don't have to change it later.

2 We can change the size of the letters. Click on the size button and select the size you want before you start to write. To change the size of something already written, select the text with the left mouse button and change the size.

3 We can also underline, click on "U" (underline) to start writing with underline or select text with the mouse and then click on "U".

4 To change the colour of the text, we do the same as for size or underline. When we click on the colour button we have different colours to choose; choose the one you would like.

5 We can change from one menu to another, for example click on "Page Layout". There are several layout options, for example we can change the margins. Click and hold with the left mouse button on the triangular/rectangular margin sign and drag right or left. The margin changes immediately.

6 We can also change the colour of the page.

7 The "Indent" is the distance from the margin to the start 116/ 128 end ("After") of the line.

9 The "ribbon" is the area with the sub-menus, we can hide it to have more screen space. Click near the bottom of the ribbon with the right mouse button and select "minimize the Ribbon" To see the ribbon again, click on any of the main menu options, the ribbon temporarily shows. We can click again near 117 128 button and de-select minimize the Ribbon"

10 In the insert menu we can insert "Shapes." Click on Shapes and insert an "oval" (the second "Basic Shape" and two other shapes that you like.

All the things that we can do in Word are in the menus, but sometimes it is faster to use the "special keys" of the keyboard. To use them, we press at the same time a special key and another key. For example: Ctrl+b If we press the "control" key and the "b" key the text becomes bold.

Ctrl+c To copy text, images, etc. we select with the mouse the text/image that we want to copy and then we press the "control" key and the "c" key.

Ctrl+v To paste text, images, etc. we click with the mouse where we want to paste the text/image and then we press the "control" key and the "v" key.

Alt + print screen (sometimes only "print screen") it copies what is on the screen as an image. Then we can paste the image in another place, or print it.

Alt + v + u the menus disappear and we can see the document better. To see the menus again, click on the "Esc" key, on the top left corner of your keyboard.