Hardware

The CPU, or the 'Central Processing Unit', is the main component of a computer system. It is responsible for making calculations and controlling the system. There are two parts of the CPU, the ALU, or 'Arithmetic and Logic Unit', which is responsible for mathematics and logical operations, and the Control Unit, which executes instructions of programs stored in the RAM by using electrical signals. The CPU uses a system called Fetch-Decode-Execute, where the CPU fetches an instruction from it's memory, works out what the instruction requires, then carries out that action.

The CPU needs two things in order to function: the RAM, or 'Random Access Memory', which is where programs are stored once they have been loaded, and the Cache Memory, which is used to store data that is waiting to be processed. The Cache Memory is very fast and is located very close to the CPU in order to reduce the time it takes the data to travel.

The RAM and the Cache are known as Primary Storage, while the Hard Drive and other storage devices such as Flash Memory Drives, are known as secondary storage, and are designed to hold data while the computer is turned off.

An in depth look at the history of a CPU, as well as how it functions: HowStuffWorks: How Microprocessors Work

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Binary Logic

AND Gate:

 

'AND' Gates will have an output set to 0, unless both inputs are equal to 1.

OR Gate:

 

'OR' Gates will always output 1 so long as at least 1 input is set to 1.

 

 

NOT Gate:

 

 

'NOT' Gates will always output the opposite of the input.

 

AND/NOT Gate:

'AND/NOT' Gates will always output 1 unless both inputs are equal to 1. This is because the NOT gate reverses the output of the AND gate.

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Binary is a Base-2 Numeral System made up entirely of 1's and 0's. These two numbers correspond to "On" and "Off" respectively. A document published by John von Neumann in 1945 stated that all data and instructions for a modern computer should be stored in binary. Binary is used to manipulate transistors in the computer, to give instructions to the processor.

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Memory

ROM - Read Only Memory - Used to store the firmware that checks for errors upon turning on a computer, then handing control over to the operating system. The ROM can be found on the motherboard.

RAM - Random Access Memory - Allows the access of data in a random order, and stores programs that are currently in use. The most widely used form of RAM today is DRAM, which isn't technically random access, but still stores programs being used.

Cache - Stores data that is about to be used, or has just been used, to allow the CPU  to access it quickly. Is located near the CPU to allow for faster access.

Flash - Flash Memory is a type of storage that is re-writeable, and is useful for transferring data around very quickly. Solid State Drives and USB Drives take advantage of this technology.

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RAM, or Random Access Memory, is the primary form of computer memory. Programs that are currently in use are stored in the RAM, including the Operating System. RAM is volatile, and must be constantly powered or the data will be lost. Therefore, it isn't a good way of storing data in the long term, so a hard drive is used instead.



Data is transferred to the RAM from the Secondary Storage, usually a hard drive, and from there it is transferred to the cache memory. The Cache Memory is located near the CPU for quick transfer speeds and stores data that is about to be used, or that has just been used. From here, the data is sent to the CPU, which performs the task the data requires.

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Input, Output and Specialist Needs

Input  devices allow the user to control an output device, such as a computer. For example, a mouse allows you to move a cursor on screen, allowing for easy navigation around a computer. An Output device, such as a computer monitor, displays the result of an input device, for example, a computer printer outputs a picture or text that was created on the input device (a computer).



Some users may have specific needs for an input or output device. For example, for a person who has limited movement in their body, the Eye-typer was invented. This allows the user to input data by blinking, and the eye-typer detects the blink and sends that information to the computer. Another, more commonly used specialist input is voice control, which is commonly used in mobile phones, and allows users to speak commands into the phone instead of navigating around a touch screen.

Another example of an input device is a game controller. Valve is attempting to change the way this particular device works with their unusual controller which uses two touch pads instead of the more standard analogue sticks, to give a more "keyboard and mouse" type feel to those playing games on a big screen.




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Secondary Storage is used to store data when the computer is turned off. The most common form of secondary storage is a hard drive, or more specifically, a magnetic hard drive. These are commonly used as they are cheap, reliable, it has a high capacity of storage, and are easy to manufacture in large amounts. A standard magnetic drive can cost as little as £0.027 per GB.



Recently, flash memory is beginning to become a more common form of large capacity secondary storage. Solid State Drives (SSDs) can be bought for as little as £0.33 per GB and have a much faster read/write speed than a magnetic drive. They also have no moving parts, so are far more reliable and less likely to break and corrupt your data. Unfortunately, the price still isn't low enough for them to fully replace magnetic drives, but eventually the price might go low enough that this will be possible.



Optical Discs such as a CD, DVD or Blu-Ray are still in common use today. Dual-Layer Blu-Ray discs can hold up to 50GB, and are constantly getting cheaper which allows them to still be used, even though some people think discs are a dated technology.