What is a CPU?
CPU stands for Central Processing Unit. It is the core of every computer system.The CPU is needed to execute programs, processing inputs and producing outputs. It does this using the fetch-execute cycle. The Data and Program which is needed is stored into the RAM (Random Access Memory). The CPU then decodes the program. The CPU understands a specific set of commands called Instruction Sets. The CPU then executes the program.
The CPU has 2 components:
- The Control Unit - This directs systems to execute instructions using electrical signals.
- The ALU (Arithmetic and Logic Unit) - This carries out all the arithmetic and logical operations.
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Binary Logic
Binary is a number system that uses the digits 0 and 1 to represent all numbers. Binary can be represented by electronic components set to ON or OFF (just like a switch).Logic gates are found in the computer. These are electronic switches that are connected together. How the logic gates are arranged determines how it manipulates the input signal.
There are 3 main logic gates:
AND logic gate.
All outputs are 0 unless 1 in inputted in both inputs.
NOT logic gate
The NOT logic gate gives an output opposite to what is inputted.
OR logic gate
The OR logic gate is the opposite of the AND gate. All outputs are 1 unless 0 is inputted in both inputs.
AndNot logic gate
Computer Memory
RAM - Stands for Random Access Memory. RAM is needed to run the operating system and other applications. Programs are stored in the hard drive of the computer. When they are needed they're loaded into RAM. The data in RAM can be processed by the CPU, the CPU can carry out the fetch-execute cycle. RAM memory is short term and volatile, the RAM is emptied when it's turned off. The larger the RAM on a computer, the faster it can run.ROM - Stands for Read Only Memory. It can't be changed by a program or user, it can only be read. It stores the boot program which, in turn, boots up the operating system.
Cache - Cache memory is often built into the CPU.
Flash - Flash is a form of removal memory. A USB drive is a form of flash memory.
Virtual -
Input and Output Devices
Input - An Input Device is something that enters data into a computer.Examples of Input Devices:
- Keyboard
- Mouse
- Microphone
- Touch Screen
Output - An Output Device is something that displays data that has been processed. Data can be displayed in images, text, and sound.
Examples of Output devices:
- Computer Monitor
- Printers
- Speakers
Specific Needs
Input and Output devices can be adapted to aid people with specific needs.
For example, a keyboard can be built with brail instead of printed letters to aid those with a sight impediment.
Instead of a mouse operated by hand, they can be operated by a foot.
These adaptations are important because they make using technology more available for people with disabilities.
Secondary Storage
Secondary Storage is a way of storing data when the power is off. Secondary storage is non volatile.Without secondary storage, we would be unable to save data when we turn of the computer.
The hard disk is the most common form of secondary storage. It is the largest data storage device in a computer.
CD's and DVD's are optical.
The are very cheap to make and are easy to distribute.
CD's can hold around 700MB of data whereas a DVD can hold up to 4.7GB.
