Computer Systems Flashcards
overflow
the calculation goes over the amount of bits the computer can deal with
Binary
A way of representing information using only two options.
Hexademical
easier to read as a human
ASCII
American Standard Code for Information Interchange
extended ASCII
8 bit which can code for all foreign characters
Unicode
can fit all language characters and more
colour depth
the number of available colours is 2^(n)
Image file size (bits)
Image size (area) x colour depth
Sampling
converting analog sound to digital sound
Sample rate
the number of samples taken per second
Bit depth (sound)
how many bits is used
Sound file size (in bits)
Sample rate x Bit depth x Time running (seconds)
compression
reducing file size
Lossy compression
Losses bits of data by using abstraction and then filling in with what it predicts
Lossless compression
No data is lost. Repeats recurring information
Huffman tree
A tree having the nodes representing symbols as the leaves, with more frequent symbols having nodes progressively closer to the root. The most frequent symbols are the closest to the root node. Note that internal nodes cannot represent symbols.
The edges connecting children to parents are either 0 or 1. Convention must be established (e.g., left children have 0s, right children have 1s).
The code for a symbol is built from 0s and 1s along the path from the root down to the desired symbol.
Codes must be prefix free.
abc:7
/ \
ab:3 c:4
/ \
a:1 b:2
Run Length Encoding (RLE)
wbbw becomes 1w2b1w
System Software
System that manages the operation of the computer (controls hardware)
Embedded system
Coded for 1 purpose (washing machine)
CPU (Central Processing Unit)
Where data processing takes place
FDE (Fetch Decode Execute) cycle
Data fetches information, decodes it and then executes task
Control Unit (CU)
controls operations of the CPU’s internal components
Address bus
These transfers data to and from the CPU
Control bus
Controls whether the busses are occupied
Data bus
Transfers data between the processor and memory
Analogy for CPU and CU
the busses in CU are nerves, the CPU is the brain
ROM (Read Only Memory)
Contains operating system, can’t delete and is non-volatile
RAM (Random Access Memory)
All open applications, deletes when turned off (volatile)
BIOS
Controls what happens when the computer is switched off
Registers
Cache memory above the CPU
ALU (Arithmetic Logic Unit)
Deals with arithmetic and logic operations
Clock
Synchronises all components, higher clock speed means more FDE cycles
Cache
Memory that is used to make a computer work faster
Cores
Can split the processes between the cores which means it will be faster
Magnetic storage
- Moving parts so not portable
- low cost for lots of storage
- not always reliable
Solid state drives
- uses electricity
- expensive for not as much storage
- easy to transfer data
- portable
optical disk storage
- hits pit or grove to provide 1 or 0
- cheap
- fragile
- low storage
Cloud storage
- easily accessed and multiple access
- needs internet
- could be hacked
- can’t be lost
Memory management
Allocates data to RAM and makes sure there is enough space
Virtual memory
process of optimizing RAM storage by borrowing hard drive space
Processor management
prioritises tasks and allocates time to each process
Peripheral Management
communicates with peripherals through drivers
Application management
Assigns memory space and processor time to applications
Security management
Protects against viruses and malicious malware
User Interface
Converts computer code into visible icons for user to understand
Anti-virus software
A program that finds and removes viruses from a computer
Encryption software
Scrambles data to stop third parties from accessing it
Firewall
Prevents unauthorised access to a computer over a network
Spyware detectors
block or removes programs collecting personal data
System cleanup
Search and remove files no longer needed
File compression software
makes files smaller to be transmitted more easily
High level languages
Faster program development
Low level languages
- requires less memory
- easier to debug
Machine code
machine-level instructions that are uniquely read by computer processors using patterns of 1s and 0s.
Assembly code
A low level language that uses mnemonics to represent machine code instructions
