STORAGE DEVICES

Hard disk drives are an internal, higher capacity drive which also stores the operating system which runs when you power on the computer.

Measures: computers have a very element way to store data: they can remember only 0 or 1. A value of 0 or 1 is called bit and all computer data are stored as sequences of bits. a sequence of 8 bits is called a byte which is a quantity large

enough to store usually a letter or a digit (even though sometimes 2 bytes are necessary). Modern computers are able to deal with enormous quantity of bytes, forcing us to introduce other quantities:

• Kilobyte (KB) approximately 1,000 bytes,
• Megabyte (MB) approximately 1,000 KB or one million bytes,
•  Gigabyte (GB) approximately 1,000MB or One billion bytes,
• Terabyte (TB) approximately 1,000 GB or one trillion bytes.

Usually the unformatted text of a whole book can fit in some KB, while for an image I good resolution (let’s say ready to be printed on A4 paper) or for a modern song some MB required, while a film in high quality needs some GB.

Devices: the Computer uses several devices to permanently store and move data, which vary a lot in terms of capability, cost, speed and portability.

The most used is the Internal hard disk, which usually is inside the computer box and can not be moved, its size currently ranges from 500GB to 2 TB. On the other hand, an External Hard disk, is outside the computer, has the same size and obviously can be moved. Its only disadvantage is being slightly slower.

SSD Solid State Drives are starting to slowly invade the market. They are not disks at all, but very large memory cards shaped like a hard disks which can entirely replace the internal hard disk. Their main advantages are that not having moving parts (they do not rotate at high speed like hard disks) are more robust and that in most situations they are faster than hard disks ( up to 10 times faster). Their disadvantage is the limited size which currently is 500 GB and their high price.

CD and DVD is an alternative way to store data. They contain about 700 MB and 4 GB, respectively. They are divided into R which may only be written once and RW which may be written and re-written several times. They require a CD-reader or DVD-reader to be read, which are available on most computers. A new generation of high capacity discs has appeared on the market, the Blue-ray with 25 GB size.

Memory Stick or USB Pen Drive is the most used way to temporary store and move data. Its size is now up to 64 GB, however its reliability is not perfect, therefore it is used mostly to move data.

Microprocessors:  "The brain of the computer“

PCs primarily use microprocessors (sometimes called the chip). The older Intel versions include the 386, 486 and now the Pentium line.

The CPU (Central Processing Unit)is normally an Intel Pentium (or equivalent) and it is one of the most important components within your computer.

•  It determines how fast your computer will run and is measured by its MHz speed.
• Thus a 600 MHz Pentium is much faster than say a 400 MHz Pentium CPU.
• It is the CPU that performs all the calculations within the computer.

Some of the Factors That Impact on a Computer's Performance

_ CPU speed

_ RAM size

_ Hard disk speed and capacity