Component 1 - Computer Systems Flashcards
What affects the CPU speed?
- Clock Speed
- Number of Cores
- Cache Size
- SSD
PC (Program Counter)
Holds memory address of the instruction for each cycle
Accumulator
Holds answers from the ALU
MAR
Holds address that’s about to be used by the CPU
MDR
Holds the data of the current cycle
FDE cycle
- Instruction is taken from the Main Memory and stored in a register
- Instruction is decoded by ALU and stored in Accumulator
- CPU then carries out the decoded instruction
Volatile Memory
- Memory than needs power to stay on, RAM
Non-Volatile Memory
- Memory that keeps its contents always, ROM
ROM
- ROM cannot be changed and holds Bootstrap Loader
RAM
- Holds all Programs currently in use
Features that you look for storage?
- Robust
- Portability
- Durability
- Speed
- Price
Virtual Memory
- Used as extra space for the RAM, located on Hard Disk
Tertiary Storage
- Backing up large amounts of data
Primary Storage
- Memory with small capacity but is fast compared to secondary storage
- Usually volatile (besides ROM)
Secondary Storage
- Bigger but slower compared to Primary Storage
- All is Non-Volatile
Embedded System
- Computer device built into another device for a specific purpose
Features of Von Neuman Architecture
- Data and Instructions stored in Main Memory
- Computer split into many components, each with a different task
What are programs made up of
- Instructions and Data stored in Main Memory
BIOS (Basic Input Output System)
Built in core to start computer
What is the ALU
Performs Logic Operations and Calculations
Control Unit
Manages the FDE cycle, controls flow of data in/out the CPU
Cache
Stores frequently used memory close to the CPU so it can accessed quickly
3 Parts of the CPU
- Cache
- CU
- ALU
GPU (Graphical Processing Unit)
Handles graphics/image processing
Optical Storage (CD, DVD’s, Blue-Ray)
- Cheap, Portable
- Small Storage, Unreliable, Slow Read/Writes
- Comes in 3 forms: Read Only/Write Once/Rewritable
Magnetic Storage (Cassettes)
- Cheap, High Storage
- Read/Write sequentially, have to find specific data by looking from start to end
Solid State Drives (SSD)
- Fast Read/Writes, Durable, High Capacity, Robust
- Expensive
- Most SSD use Flash Memory and allows Hybrid Drivers to store the OS/Programmes
Hard Disk Drives (HDD)
- High Capacity, Cheaper than SSD’s
- Moving Parts, Noisy
System Software
Maintains a computer’s hardware/programmes
Operating System (OS)
- Manage Hardware/Software
- Provides GUI, Multi-Tasking, Security and Account Managing
- Deals with File/Disk Management, defragments
Device Drivers
- Allows OS and Hardware to communicate
- OS may install Driver update automatically/ask for consent
Hardware
Physical Pre-Built Components on a Computer/Physical peripherals
Software
Applications/Programmes that run on the computer
Defragmentation Utility
Orders fragmented files (scattered files) to free space and improve read/write speeds, usually on HDD’s
Compression Utility
- (De)/Compresses files on computer, can be reverted
- Quicker to download/send and websites may have file size limits
Utility Software
Maintain/Configure a Computer
Encryption Software
- Makes data readable only for intended users
- Stop hackers stealing data
- Encryption key needed
Types of Data measurements
Bits - Smaller Measure of Data Nibble - 4 Bits Byte - 2 Nibbles (8 Bytes) Kilobytes - 1000 Bytes Megabytes - 1000 Kilobytes Gigabytes - 1000 Megabytes Terabyte - 1000 Gigabytes
Binary Shift
Left - n amount of shifts to left is multiplied by 2^n
Right - n amount of shifts to right is divided by 2^n
Binary Overflow
If 8-bit binary exceeds 8 bits, add on n amount of 0’s on start/end depending on amount of left/right shifts
Lossy Compression
- Reduces file size greatly, but irreversible
- Lossy Formats: JPEG and GIF
Lossless Compression
- Reduces file size by a bit, can be restored
- Removes unnoticeable data
- Lossless Formats: BMP, PNG, RAW
Character Sets
Group of Characters the computer understands based on their Binary Code
(Extended) ASCII
- English words only, ASCII is 7-bit Binary code, 2^7
- Extended ASCII is 8-bit Binary code, 2^8, so it can represent more characters
Unicode
- Covers many languages and their characters
- Needs much more Bytes than ASCII because they cover more characters
File Size (Bits) =
Bits per Character x Number of Characters
Images
Images are usually Bitmaps, an arrangement of Pixels, more Pixels means better Image Resolution
Colour Depth
- 2^n, greater the value of n is = more bits per Pixel
- More bits = More colours, increasing Image Quality
Image File Size (Bits) =
Image Resolution (Length x Width) x Colour Depth
Sound
- Sampled digitally as an analogue signal
- Analogue Signals convert into digital data for computers to read/store, “sampling”
Sample Rate
Amount of Samples per second (Hz)
Sound Bit Depth
Number of bits of each sample, more bits mean better quality
Sound File Size (Bits) =
Sample Rate (Hz) x Bit Depth x Duration of Sample (s)
LAN
- Covers a small area <10km usually on a single site
- LAN is owned by the consumer, cheap
- Used in Businesses, Schools
WAN
- Covers a wide area as it a web of LANs in different location and are connected by radio/satellite links
- Telecommunications own the WAN, expensive
- Examples are The Internet
Factors that affecting Network Peformance
- Bandwidth (amount of data transferred in a given time) which is splitted
- Wired/Wireless Connection
- Hardware/Topology
NIC (Network Interface Controller)
Allows device to connect to a network, usually built on a motherboard
Switches
Connect devices together on a LAN and carries data between the devices
Routers
- Transmit data (packets) between Networks
Ethernet Cables
Cat 5/6 - Twisted Cables to reduce internal interference
Coaxial - Copper Wire with plastic layer and mesh to shield it from the outside
Fibre Optic - Transmit light as data, expensive, high peformance, no inteference
Bluetooth
Short, direct connection between 2 devices and have low bandwidth
Wi-Fi
- Connect many devices to a LAN at once
- Long range, more bandwidth
Client Server
- Managed by a server, connected to clients
- Files, passwords, users stored centerally (on server)
- Pros: Easy to keep track of files, backups/updates are easier, reliable
- Cons: Expensive, Clients fail if server fails
Peer to Peer (P2P)
- Devices connected to each other without a server
- Files stored on each device
- Pros: Easy to maintain, Devices carry on if one fails
- Cons: Backups/Update carried out serperately, less reliable and data can be lost
Star Topology (Wired/Wireless)
- Devices Connected to Switch/Server that allows access to the server
- Pros: If Device fails, others carry on, Good peformance
- Cons: If wired theres too much cabling, expensive, all devices affected if switch/server has problem
Bus Topology
Devices arranged in a line, data sent up/down the line therefore more data collisions
Ring Topology
Devices in a circle and data moves in 1 direction therefore no collision, only one device can send data at a time
Mesh Topology
- All devices connected with each other
- Pros: Network cant fail and data sent on fastest route
- Cons: Expensive, lots of cables
Network Protocols
A set of rules for how devices should communicate and how data is transmitted across a network
Identifier
Each device has one so it can be found on a network
Mac Address
- Given to all devices on same network
- Unchangeable and send data to correct devices on same network
- 48/64 bit binary numbers
IP Address
- Given to devices on any network, allows devices to communicate with other devices
Network Protocols Types
TCP - Rules on how devices connect on network
IP - Directs packets to correct place
HTTP(S) - Allow access to websites
FTP - Edit Files between devices on a network
Layers of Protocols
Page 28, 4 layers
URL’s
Addresses to access web servers
DNS
- Changes website Domain Name to its IP Address
- Easier to remember
The Cloud (Uses internet to store files)
- Pros: No physical management needed by Owner, users dont need expensive hardware, acts like a Client Server
- Cons: Expensive for Owner, Ownership of data issues, internet connection needed
Brute Force Attack
- Hacker tries several password combinations until its guessed right
- Handled with strong password and try limits
(D)DoS attack
- Pointless packets (sometimes from victim devices) sent to a server to overload/crash it
Dictionary Attack
- Same as Brute Force but more consistent as you can put in words that may help with the guesses
- Handled with unique symbols and try limits
Malware (Software to harm devices)
- Hacker may threaten your cojmputers safety for money or try gain access to the computer
Spyware
Hacker can monitor keystokes/actions on computer
Viruses
Attach themselves to files and can infect other files
Worms
Exploit weakness in network security and spread quickly
Trojan
Disguised as legitimate software to trick users into installing it
Social Engineering
- Tricking someone in order to gain access to a network
- People are usually the weak points in a system
SQL Injections
- Allow hackers to access/change database on a website
Penetration Testing
Paying a hacker to hack your own network to identify weaknesses
User Access Levels
- More secure as few high access users can access sensitive data
Firewall
Protects a safe network from a unsafe network
Encryption
Encrypts data sent over a network, packet sniffers cant use this data and only reciever can with encryption key
