Hardware

 CPU

A CPU, or Central Processing Unit, is the most important part of a computer, there are 2 parts in the CPU, the control unit and the ALU. The control unit is for controling the data flow and the ALU is for performing arithmetic and logical operations. It controls the processing and executes the instructions stored in computer programs. To do this, the CPU has to access two things. The RAM and the cache memory. The RAM, or random access memory, is where the programs waiting to be run are stored. The cache memory is where we store data waiting to be processed, it is close to the CPU so it can be quickly accessed by the processor, therefore making the frequently used data easy to find. These are called primary storage. Secondary storage is the hard drive and any other device like it, for example, USB flash drives or SSDs, this is where data is stored when the computer is off/not in use. The CPUs main function is the fetch-execute cycle. The CPU processes programs from the main memory, then it fetches the next instruction, decodes it and executes it. 

Memory

• RAM (random access memory) is the information stored to be accessed quickly from random locations. This is volatile data so if the computer powers off the data is lost. The RAM usually consists of the os on load up as well as any programs you are running etc.
• ROM (read only memory) is a type of "built-in" memory that is capable of holding data and having that data read from the chip, but not written to. Unlike Random Access Memory (RAM), ROM is non-volatile which means it keeps its contents regardless if it has power or not. It is usually very small and used to store the files used for boot up.
• Virtual memory is used when the RAM is fully used up. When there isn't enough RAM to cater to all the demands of the system, a section of the hard drive is used to store data in the RAM that is not currently used whereas it is loaded into the RAM when and if it is needed. This makes for considerably longer times when switching between programs as the system has to load the program from the virtual memory to the RAM before it can be used.

Input/Output Devices

A computer needs to be able to to get data and information in and out of its system. To do this we use Input and output devices. Something sends data to the system which interprets it and sends an output, through the same or a different device. Common examples of these devices are keyboards and mouses. A revolutionary new idea for these devices are the new steam controller, this uses haptic feedback to enhance your game. The input would be you using the controller and the output would be the game playing and receiving haptic feedback.

Secondary Storage

Secondary storage is used to store data when the power is off (non-volatile). There are three common types of secondary storage:

• Magnetic hard disk:
• Reliable
• High capacity at low cost
• Can be internal or external for backup or transfer of data
• http://tinyurl.com/ptsao3d
• Optical Disk
• CD or DVD
• High capacity at low cost
• Small
• Robust and multiple uses
• Slower than hard disk/flash ROM
• http://tinyurl.com/cdscomputing
• Flash(Solid State) Memory
• Read only
• Fast access
• Low Power
• Small
• Light 
• Robust
• Inexpensive at lowish capacities but expensive at high capacities
• http://tinyurl.com/ssdssdssdssd