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What does the FDE cycle stand for?
fetch decode execute cycle
What happens in the fetch stage of the FDE cycle?
An instruction is fetched from memory.
What happens in the decode stage of the FDE cycle?
The instruction is decoded.
What happens in the execute stage of the FDE cycle?
The decoded instruction is executed so that the CPU performs it continuously
the PC is incremented
the instruction is transferred to the MDR
the address of the next instruction to be fetched is placed in the MAR.
What are the 4 registers?
MAR, MDR, PC and ACC./Memory address register, memory data register, program counter, accumulator
What does MAR stand for?
Memory Address Register
What does MDR stand for?
Memory Data Register
What does ACC stand for?
Accumulator
What does PC stand for?
Program Counter
What does the MAR do?
Stores the address of the next instruction to be accessed.
What does the MDR do?
Stores the data to be brought / sent from the main memory.
What does the ACC do?
Stores the results of arithmetic operations.
What does the PC do?
Stores the address of the next instruction to be accessed and gets incremented every FDE cycle.
What are the 3 CPU components?
Cache, CU, ALU.
What does CU stand for?
Control Unit
What does ALU stand for?
Arithmetic Logic Unit
What does cache do?
Store frequently used instructions.
What does the the CU do?
Controls inputs / outputs of data to and from the CPU, controls the timing of signals sent within the CPU and it controls the flow of data within the CPU.
What does the ALU do?
Carries out arithmetic calculations and logic operations.
What is clock speed?
The number FDE cycles carried out per second.
What is clock speed measured in?
Hertz usually Giga hertz, where giga means 1 billion.
Why does having more cache increase the performance of a CPU?
More cache reduces the need for the CPU to go to the RAM, cache is faster than RAM so this makes the CPU run faster.
What is cache?
Primary memory, built onto the CPU.
What does having multiple cores allow for?
Parallel processing.
What is parallel processing?
When each processor executes a separate instruction at the same time, each processor (core) can run a different program at the same time, parallel processing enables multitasking.
What are the advantages of having multiple cores?
It will, most of the time, increase performance.
What are the disadvantages of having multiple cores?
Some software can't be split between multiple cores so the performance won't increase.
What is embedded system?
A computer system that is built onto another device, has limited functions and is not a general purpose computer.
What are the advantages of an embedded system?
Cheaper than a general purpose computer, tend to require less power.
What are the disadvantages of a general purpose computer?
Has limited functions.
Give 2 examples of embedded systems.
Washing machines and ovens.
What is primary storage?
Storage that is directly connected to the CPU, it is needed because the CPU can't directly communicate with the CPU and it is usually faster than secondary storage.
What does RAM stand for?
Random access memory?
What does RAM do?
Stores currently running programs.
What does ROM stand for?
Read only memory
What does ROM do?
Stores the BIOS
What is virtual memory?
The usage of secondary storage as RAM once RAM is full
What is secondary storage?
Non volatile memory needed to store data permanently
What are the 3 types of secondary storage?
Optical, magnetic and solid state
What are the key characteristics of optical storage?
Portable, robust, cheap, very slow
What are the key characteristics of magnetic storage?
Relatively cheap, large capacity, not durable, not portable
What are the key characteristics of solid state storage?
Very expensive, very fast, portable, durable
What are the 6 characteristics to consider when buying secondary storage?
Capacity, cost, speed, portability, reliability, durability.
What is 1 bit?
A single 1 or 0
What is a nibble?
4 bits
What is 1 byte?
8 bits
What is 1 kilobyte?
1000 bytes
What is 1 megabyte?
1000 kilobytes
What is 1 gigabyte?
1000 megabytes
What is 1 terabyte?
1000 gigabytes
What is 1 petabyte?
1000 terabytes
What is 10110010 in denary?
178
What is hexadecimal?
A number system using base 16 that represents 0 through 15 with digits 0 through 9 and letters A through F
What is a binary left shift?
Moving all the digits in the binary number to the left, and adding a 0 to the least significant bit
What is a binary right shift?
Moving all the digits of the binary number to the right
What is an arithmetic left shift?
Moving all the digits of the binary number to the left, preserving the most significant bit and replacing the least significant bit with 0
What is an arithmetic right shift?
Moving all the digits of the binary number to the right, preserving the most significant bit
Perform an arithmetic left shift on: 1101 1001
1011 0010
Perform an arithmetic right shift on: 0110 1011
0011 0101
What does ASCII stand for?
American Standard Code for Information Interchange
How many bits does ASCII use?
It has 8 bits but only uses 7 bits.
How many bits does extended ASCII use?
8 bits.
How many bits does Unicode use?
32 bits.
What does ASCII represent?
The main characters in English.
What does extended ASCII represent?
All characters in the English language.
What does Unicode represent?
Every character in various languages around the world.
What is a bitmap?
An image made up of pixels, each pixel has a unique binary code that represents its colour.
What is colour depth?
The number of bits per pixel.
What is PPI?
The number of pixels per inch.
What is sampling?
Analogue (real world) sound must be sampled and stored in binary, the amplitude of the waveform is sampled/measured, this amplitude is converted into binary.
What is sample rate?
The number of samples taken per second
What is bit depth?
The number of bits per sample taken.
What is metadata?
Data about the image file / properties of the file.
Give 2 example of metadata.
Colour depth and resolution.
How does colour depth affect file size and quality?
Both file size and quality increase.
How does sample rate affect file size and quality?
Both file size and quality increase.
How does bit depth affect file size and quality?
Both file size and quality increase.
Why is compression needed?
To reduce file size, for faster upload / download speeds, and because it takes up less space on the secondary storage.
What is lossy compression?
Data is permanently lost, it reduces the file size, quality is reduced and it uses an algorithm to remove unnecessary data.
What is lossless compression?
Data is temporarily lost, but comes back when the file is decompressed.
What does it mean if memory is volatile?
When power is lost, data is lost.
What does it mean if memory is non-volatile?
When power is lost, data is not lost.
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1+0 = 1
1+1 = 10
1+1+1 = 11
Perform a binary shift of 2 to the left on this binary number 00110101.
Add these 2 binary numbers. 00110101 + 10011011
What does LAN stand for?
Local Area Network
What does WAN stand for?
Wide Area Network
What is a LAN?
Covers small geographical area and hardware is owned by the organisation.
What is a WAN?
A network that has a large geographical area and is owned by a telecommunications company.
What factors affect network performance?
Distance from router (wireless), walls inbetween router and device (wireless), amount of data being transferred, number of users and available bandwidth.
What is a client?
A computer that relies on other computers (servers) to provide and manage data.
What is peer to peer?
All devices have equal status, their is no central server, easy to maintain, cheap to setup. There is no dependence on ones node, if one device fails only the data on that device will become inaccessible. The network will still operate without that node.
What does WAP stand for?
Wireless access point.
What is a router?
Connects the network to the internet.
How does a router connect a network to the internet?
Sends packets to a destination, receives packets from the internet, forwards packets to other computers on the internet, connects (different) networks together, has a public IP address for the LAN, designates private IP address to network nodes.
What does a switch do?
Connects devices together, receives data packets, sends packets (only to their destination), creates a list of devices connected to it as it receives signals and uses MAC addresses of the devices connected to it.
What does NIC stand for?
Network Interface Card
