Optical Storage Optical Storage o Examples of Optical

Optical Storage

Optical Storage o - Examples of Optical Storage include: CD-ROM CD-RW DVD-ROM DVD-RW

Magnetic Storage o - Examples: Floppy Disk Drives Hard Drives Zip Drive Magnetic Tape

Magnetic storage o Data is stored by magnetising the surface of a flat, circular plate. o These plates constantly rotate at a high speed. o A read/write head floats on a cushion of air just above the plates surface. o The drive is inside a sealed unit because a speck of dust could cause heads to crash.

Capacity o o o This is how much data a type of storage media can hold. Examples are shown below: Floppy Disk capacity – 1. 44 Mb CD ROM Capacity – 700 Mb or 80 Mins DVD ROM Capacity – 4. 7 Gb or 2 ½ Hours

Access o 2 TYPES OF ACCESS: - DIRECT/RANDOM - SERIAL

Direct Access o o o The systems can go straight to the data it requires. A disk is a Random/Direct Access medium Makes this faster method of data storage than serial storage

Serial Access o One example is a Magnetic Tape Drive. o Slow o o Must ‘travel’ through various storage locations to get to required data. Think of an audio tape (if you remember these!)

Interface o A Hardware Device o Required to allow the processor to communicate with an external or internal device. o Sometimes the Interface is a board in the computer. o Other times the Interface is a connection to a port.

Why an Interface? o o - Different characteristics between the peripheral device and the processor. These characteristics include: Data Conversion Speed of Operation Temporary Storage of Data

Types of interface o Most common type = ANALOGUE to DIGITAL signal o o Peripheral accepts an Analogue Signal but must be converted in order for the processor to use the data. Examples – Sound & Pictures

Interfaces o o o The processor works at a speed in time with its internal clock. The processor works at a much faster rate than the peripherals. It is this difference in speed that requires the Interface to allow the device and the processor to work together.

Data Storage o o Data needs to be held temporarily in transit between the processor and a device. This allows the processor to continue with other tasks instead of standing idle. o This data is held in a ‘buffer’. o Printers have a buffer to hold data about to be printed. o Keyboard characters are stored in a buffer while they are being processed.

Inteface options o o o 4 Interface options to consider when buying a device. PC Card, Parallel Port, USB 2. 0, IEEE 1394 Firewire, Serial Port, IDE, SCSI Most users favour USB 2. 0 and Firewire because of their connection speeds and flexibility.

Speed of operation o - In terms of: Pages Per Minute (PPM) Frames Per Second (FPS) Megabytes Per Second (MBps) Megabits Per Second (Mbps)

exercise o Exercise 5 – p. 96 -97 LTS Computing Notes