comp sci corrections

subprogram

self contained block of code that performs a specific task

decomposition (subprogram)

can be reused by calling

abstraction (subprogram)

programmer using subprogram does not have to know it works, subprograms can call other subprograms, higher and higher levels of abstraction to simplify problem solving, can use arguments/parameters so code can be used in different contexts

a flag

used to identify whether an identifier is true or false

arrays

all same data type

lists

used to hold multiple data items

%

modulus, returns remainder

//

floor division, rounds down

linear search

compares first value to target, if not correct moves to next value until end of list

brute force algorithm

tries every possibility until solution found or all possibilities exhausted

divide and conquer

where half the list is discarded each pass

index of median item

[index of last item] + [index of first item] // 2

merge sort

more efficient to solve large problem by dividing into smaller problems and solving, divide list into sublists then sort

binary search

data must be sorted

best case scenario

linear search faster, as binary search would have to split list first

small list

linear search may find faster?

arithmetic

copies MSB, logical

imprecise result

discards/truncates after decimal place

overflow

answer uses memory that does not exist in the register

character set

list of binary codes that soft/hardware can recognise to represent a value

foreign characters may not fit into 7 bit ASCII

sample rate

number of samples taken/second

file size

affected by sample rate, bit depth, length of recording and number of channels (mono/stereo)

computer memory is random access

can be accessed in any order

CU

fetches program from main memory, decodes it and controls other parts of the system to execute it

ALU

performs arithmetic and logical operations

registers

provides direct

registers

some specific function, some general purpose

FDE cycle

memory address put onto address bus, CU sends read signal down control bus, instruction at memory location placed on data bus and sent to CPU, where controls execution in other parts of system

components of embedded systems

microcontroller, sensors, battery

scheduling algorithm

used by OS to ensure that all processes get a slot of CPU time depending on priority

paging algorithm

used by OS to decide which processes to assign to which memory address

active process

currently being executed by CPU, inactive process

virtual memory

area of hard drive used to temporarily store processes when RAM becomes full

device driver

interface for OS to communicate with peripheral device

fragmented

no longer able to store file in one location and must be split up

defragmentation

fewer disc accesses needed to read data

antimalware

compares signatures to signature file, or uses rules to detect suspicious behaviour

robust software

does not crash with unexpected inputs, free from security vulnerabilities

drawbacks of high level languages

less efficient, use more memory because not optimised to make most of features of CPU

interpreted languages

quicker to test, easier to make changes (no source code)

IP address

used to uniquely identify each device connected to the internet

URL

uniform resource locator, used to identify unique resource on the internet

domain name

website name part of URL

DNS server

translates URL to IP address

wired

higher transder speeds, lower latency

NFC

radio waves used, encrypted data, devices must be in close proximity

enable devices on a network to communicate, define how data is formatted, transmitted and received

protocol stack

hierachical set of network protocols that enable devices to communicate over a network

more nodes on a bus network

more collisions

disposing electronics

landfill leaching into eco systems, burning ewaste releases carcinogens, reclaiming precious metals damaging to workers

responsible recycling

reduces chance of chemical leakage, recovers valueable and non

reducing environmental impact of digital devices

improve energy efficiency, site data centres in places where they can be fuelled by renewable power

IoT device ethical concern

may be given to third parties because unclear who owns data

AI

intelligent behaviour and actions normally associated with humans coming from computer systemsl

biased AI

biased training data, biases amplified by algorithms, programmers coding in prejudice

accountability in AI systems

designed to make autonomous decisions

IP

any unique creation of the human mind

creative commons license

allows use of product, but with certain constraints imposed

propriety software

source code legally protected by copyright, better tested so less bugs

malware

short for malicious software, desgined to cause damage or disruption, or to gain access to sensitive data

social engineering

exploits human behaviour and emotions to gain sensitive information or download malware

pretexting

pretending to be an organisation, with an invented pretext

social engineering more of a threat as no technical knowledge is needed