**Input devices** 1- you communicate with the computer via an input device. 2- Input devices allow us to send information to the CPU to tell the computer what to do. **Output devices** The computer communicates its results to you via output devices. Output devices receive information from the CPU and translate it into sound or images that we can understand.

**Keyboard** 1- It used to input data to the computer. 2- It used to enter commands, select menu options. 3- It used to enter data into applications.

**Mouse** 1- It used to point and click on items, icons, menus on the screen 2- when you move the mouse a pointer on the screen moves. 3- you can activate commands or program options.

**Light Pen** 1- It is a special pen that lets you draw directly onto the screen. 2- It used to click on buttons and menus.

**Touch Screen** 1- It is similar to TV screen. 2- It has a thin transparent layer of plastic covering it, that is touch sensitive. 3- When you touch a part of the screen, it has the same effect as if you clicked on that area with a mouse.

**Joystick** 1- A hand held stick that can be moved around in any direction. 2- It used for playing games.

**Touchpad** 1- It used on laptops. 2- You can move the mouse cursor on the screen by touching the pad and moving your finger around. 3- The two buttons on the touchpad simulate the use of the left and right buttons of a mouse.

**Trackball** 1- It used instead of using a mouse. 2- You can use your thumb on the roller-ball to move the cursor on the screen.

**Graphics pad** 1- It is an electronic square piece of material that you can use to draw pictures.

**Scanner** 1- It used to scan images, documents into a computer. 2- It can be flatbed or hand held. 3- It used for optical character recognition. 4- It used to scan microfilm.

**Monitor** It is a visual display unit. 2- It is the part of a computer that displays the current process or application

**Printer** **Laser printer** It is expensive that work likes a photocopier, it has high quality print outs and print very fast. **Inkjet printer** They are small, cheap printers that use a little cartridge to spray a jet of ink onto paper.

**Plotter** It is a special type of printer that draws pictures, it used by engineers, advertisement personnel and designers who need to draw complicated diagrams.

1- Byte = 8 bits. 2- Kilobyte = 1024 bytes. 3- Megabyte = 1024 kilobytes. 4- Gigabyte = 1024 megabytes. 5- Terabyte = 1024 gigabytes.

1- A PC process data with binary digit system. 2- Bit can Be (1) or (0) 3- It used to represent data such as characters.

**Zip disks** 1- It looks like floppy disk. **Zip drives** are available in both 100 MB and 250 MB.

**Jaz disks** 1- It stores 1 to 2 GB. 2- **Jaz drives** are fast but not as a hard disk. 3- They are great for backing up information. 4- It looks like flppy disk.

**A tape drive** 1- It creats copies or backups os the files on a computer’s hard drive onto a tape cartridge. 2- The backup files can be resored in case of the original files are lost.

**Flash cards** 1- It can store anywhere hundred pictures. 2- There are three types of flash cards:- *Flash cards. *Smart media cards. *Memory sticks. 3- USB flash drive that plugs into USB port. 4- USB flash drives range in size from 16 MB to 4 GB.

**Hard disk** 1- It is a computer’s main storage device. 2- It fixed in the computer 3- It can be external hard drive outside the computer’s system unit. 4- We hear its sound at starting the computer.

**CD-ROM Disks** 1- It can hold more than 700 megabytes of data. 2- It can only read information. 3- CD-ROM drive used for reading. 4- CD-ROM stands for (Compact Disk Read Only Memory).

**Floppy disk** 1- Floppy drives read flat 3.5 inch floppy disks. 2- Floppy drives slower than hard drives and CD- ROM drives. 3- Floppy disk can only store 1.44 MB.

1- Processor speed: A computer can do billions of actions per second. 2- Reliability: Failures are usually due to human error. 3- Hard disk: * A computer can keep huge amount of data. * The more bytes your hard disk has, the more data you can store. 4- Memory: * The more memory your computer has, the more applications you can run at the same time. * Increasing memory improves system performance.

1- It is hidden inside the computer case. 2- It is an important part of the computer, known as the center processing unit (CPU). 3- The CPU is the brain of the computer. 4- The CPU does all the work, it calculate, processes and keeps things running.

1- RAM is a computer’s temporary storage place. 2- The amount of RAM or memory is a very important factor in a computer’s performance. 3- The more RAM a computer has the better its performance.