The Internet - Year 10 Project

CPU

The CPU (Central Processing Unit) is the part of the computer that processes all the instructions. It is the main component and is central to everything that happens. The CPU is involved with a cycle between it and the memory:

Fetch - an instruction is fetched from memory.
Decode - the CPU works out what to do with it.
Execute - the computer completes the instruction and does whatever it was telling it to do.

The faster the CPU the faster your computer will run. There are different factors that affect the performance of the CPU:

Clock speed - the number of fetch, decode, execute cycles per second. The more the better. A 2GHz CPU has 2,000,000,000 cycles per second.
Cache - cache is a small amount of super fast memory where the most commonly used instructions can be stored. This means it takes less time to get those instructions. The more cache you have the better.
Number of cores - having a dual core CPU is a bit like having two CPUs. A quad core is like having four CPUs. The more cores you have the more instructions can be processed at once and the faster your computer will run.

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RAM and ROM

	RAM	ROM
Purpose	A temporary storage for the programs that are currently being run.	A permanent storage for the files the computer needs to start up such as the BIOS.
Volatility	Volatile - all data is lost when the computer is switched off	Non-volatile - data is saved even when there is no power
Measure	Measured in GB e.g. "I have 8GB of RAM"	Not normally measured or mentioned in computer specs.
Fact	The more RAM you have the more programs can be run at once.	Original ROM could not be written to but now it is normally possible.

If a computer runs out of RAM it generally uses a section of the hard drive instead. This is called Virtual Memory and is much slower than RAM.

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Input and Output Devices

An input device puts data into a computer system. An output device shows information once it has been processed by the computer. Here are some examples:

Input Devices	Output Devices
Games Controller	Screen / Monitor
Number pad	Vibrations
Keyboard	Printer
Microphone	Sound
Mouse	Lights
Touchscreen	Projector
Movement Sensor	Plotter

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Input Devices for People with Specific Needs

Over the years many people have developed devices to help people with disabilities access computers. Here are some examples:


Speech Recognition	Head Mouse	On Screen Keyboard	Braille Keyboard	Puff Suck Switch

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Secondary Storage

We should think of RAM as primary storage. However the computer also has secondary storage for when files need to be stored for a long period. There are several different types:

Magnetic storage - works by making marks on a disk with a magnet. Includes old-school floppy disks and hard drives.
Optical storage - works by using a laser to make marks in a disc. Includes CD-ROM, DVD-ROM and Blu-Ray ROM.
Solid state / flash storage - makes use of flash memory to store data on a super fast, but expensive, drive.

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Memory Innovations

The creation of flash memory has brought about many innovative computer designs including:

Laptops that boot up super fast because the OS is stored on a solid state drive.
Mobile phones with huge internal storages that can hold countless videos and high definition pictures.

Other memory innovations include:

ReRAM: non-volative RAM!
Memory sticks that self destruct to protect data!
Super small 12-atom memory bits!
Memresistors for fast, dense memory.

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