1- DVD-ROM Reads the data only. This is the typical format used in
DVD players where you can place the DVD into the device to play the
video.
2- DVD-R Allows you to record onto a blank DVD once. Similar to CDR, you can record only once but the DVD can be read multiple times.
This format can be read in a DVD player as well as a DVD drive installed
on a computer.
3- DVD-RW Allows you to record multiple times onto a blank DVD as
well as being able to read multiple times. This format can be read in a
DVD player as well as a DVD drive installed on a computer.
4- DVD-RAM Similar to DVD-RW but can only be used on devices with
this specific format. These types of DVDs are usually in the form of
cartridges rather than CD.
The cost of DVD-R discs are currently lower than DVD-RW discs.
1-7 Power Supply
Every system box has a power supply that converts the AC
(Alternating Current) coming from a wall outlet to the DC (Direct
Current) needed by a computer. A power supply for a computer needs
between 5v and 12v, with 5v needed for the circuit boards and 12v for
hard drives and CD-ROMs. Newer computer systems generally use lower
voltages.
1-8 The Input/Output Devices
A computer’s Input/Output (I/O) devices allow communication
between the user and the computer. There are actually three
classifications of I/O devices you can use to:
1- send information to the computer, the keyboard, mouse, trackball ,
scanner , digitized or graphics tablets , microphones , scanners , digital
cameras , joysticks ,digital video , bar code readers , remote control , pen
reader .
2- display/transmit information from the computer, monitor, printer,
speakers , video cards , projector , data show
All of these devices are commonly connected to the back of the system
box. If a connection comes loose while you are using the computer, DO
NOT plug it back in without turning off the computer first. Otherwise,
you may damage the connection or the device.
3- communicate between computers , modems and networks cards
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