computer science vocab Flashcards
binary number system
language used in computers. anything inputted into a computer needs to be converted into binary first (in order for the computer to understand)
denary number system
language humans use every day. ordinary numbers
hexadecimal number system
humans can use hexadecimal, but in order for computers to understand it would need to be converted to binary. consists of 16 symbols (0-9 and A-F)
in binary addition, what does 0+0 equal?
0
in binary addition, what does 1+0 equal?
1
in binary addition, what does 1+1 equal?
10 (as 10 in binary is 2)
in binary addition, what does 1+1+1 equal?
11 (as 11 in binary is 3)
overflow error
occurs when a number larger than a register can store (larger than 255) is generated
what happens to a binary code when its shifted to the left?
multiplies by 2
what happens to a binary code when its shifted to the right?
divides by 2
how do you create negative binary numbers? (twos complement)
you invert 1’s to 0’s and 0’s to 1’s and simply replace/add a 1 to the right
benefits of using hexadecimal
easier for humans to understand
hex values are easier to remember and enter
what is ASCII?
a character set that represents characters using 8-bit binary numbers. (so can represent up to 256 characters).
what is unicode?
a character set that represents characters using 16-bit binary numbers (so can represent up to 65000 characters)
limitations of using binary
takes longer to decode or convert
difficult for humans to understand
lossy compression
reduces the size of a file by PERMANENTLY removing data. this method is mainly used on an image or sound file.
lossless compression
reduces the size of a file by TEMPORARILY altering data
packet header
part of a data packet. contains information about the contents of the packet and its destination
IP address
unique address that is given to a device when its connected to a network.
payload
part of data packet. consists of the actual data that the user is sending (to the receiver)
trailer
part of data packet. contains information about any error checking methods.
router
examines a data packet to obtain its destination address and send it off.
packet switching
process of transmitting data packets across a network down individual pathways
serial data transmission
data sent one bit at a time down one wire
advantages of serial data transmission
less chance of data being mixed up/misplaces (skewed)
less interference, meaning less chance of error
cheaper as only one wire is needed
disadvantages of serial data transmission
transmission of data is slower
a start and stop bit is required to be sent to allow the receiver to know where data starts and ends
parallel data transmission
multiple bits of data sent through multiple wires at the same time
advantages of parallel data transmission
transmission of data is quicker
disadvantages of parallel data transmission
high risk of data being mixed up/misplaced (skewed)
higher chance of interference, meaning higher chance of errors
more expensive as multiple wires are required
simplex data transmission
when data is transmitted from one device to another in one direction
half duplex data transmission
when data is transmitted from one device to another in both directions but NOT at the same time
full duplex data transmission
when data is transmitted from one device to another in both directions at the same time
advantages of USB
simple interface as USB can only be accessed one way, meaning less chance of errors
USB’ are fast and can transfer data quickly
disadvantages of USB
length of USB is limited (about 5 metres)
parity check
error detection method. uses either odd or even parity check. this is where you count/ sum up the 1’ present and that determines whether there is an error or not. (eg: odd parity check, two 1’ present which is an even number, so one more one must be added on the left most side in order for the 1’ to sum up an odd number)
checksum
error detection method. performs calculations on the data to create a CHECKSUM VALUE. this checksum value is then compared after transmission to see if they match
echo check
error detection method. sends copy of the transmitted data back to the sender to be compared to original data.
check digit
error detection method. used for DATA ENTRY. a calculation is performed on the data entered to create a value. then are compared with each other to see if it is correct
encryption
securing data for storage or transmission by scrambling data and making it meaningless
encryption key
algorithm to encrypt data
symmetric encryption
uses the same key to encrypt and decrypt data
asymmetric encryption
uses two different keys to encrypt and decrypt data
microprocessor
an integrated circuit that performs multiple functions of the CPU.
embedded system
computer system that performs a dedicated function. eg : traffic light, washing machine, digital alarm clock.
program counter
in the FDE cycle (fetch stage) . stores the address of the next instruction to be processed
cloud storage
data storage that is owned by a third party and accessed by the user, using the internet
static IP
does not change each time the device connects to a network
dynamic IP
can change each time the device connects to a network
MAC address
unique address that is given to a NIC by the manufacturer
network interface card (NIC)
component in a computer that is used to connect to a network
characteristics of storing data in the cloud
- you dont have to pay for the hardware
- you dont have the responsibility for the security of the hardware (however, you are relying on a third party that makes sure your data is safe)
- you can access data using different devices from anywhere that you HAVE an internet connection
- easy to increase and decrease the amount of storage space needed
characteristics of storing data locally
- need to purchase hardware
- need to make sure your data storage is well-maintained and regularly checked
- you can access data using different devices from anywhere and you DONT NEED internet connection
transistor
device that acts as a switch or gate for electronic signals
control gate
controls the flow of electric current
floating gate
can store electrical charge
virtual memory
can be used as an extension to the RAM
ROM
primary storage that store the start up instruction for the computer
primary storage
storage that is directly accessed by the CPU
secondary storage
storage that stores data permanently (until its deleted by the user)
characteristics of RAM
- volatile storage (required power to store data, if power is turned off contents of RAM are lost)
- stores data and programs that are in use by the computer
- contents are constantly changed as data is being processed by the CPU
characteristics of ROM
- non volatile storage (if power is turned off the contents of ROM are permanent)
- stores programs that initially boot the computer
- contents of ROM are fixed and usually not changed (it is possible to change it but only when computer isnt booting up properly)
magnetic storage
secondary storage that uses the properties of magnetism to store data
optical storage
secondary storage that uses lasers to store data
Solid State Storage
Secondary Storage that uses tranSiStorS to Store data
clock speed
a factor that affects a CPU’ performance. the number of FDE cycles that can be performed in a second
cache
a factor that affects a CPU’ performance. stores the most frequently used data and instructions
RAM
holds data and programs that are currently in use
system software
manages both hardware and software in a computer
operating system
manages the computer and allows the user to communicate with the computer, allowing software to run
utility program
system software that performs house-keeping activities
application software
allows the user to perform useful tasks
word processor
application software that allows the user to create text-based documents
spread sheet
application software that performs calculations on data
database
application software that stores and manipulates data
what is the process of software on a computer?
application software -> operating system -> firmware -> bootstrap
firmware
instructions stored in ROM and are loaded when computer starts
bootstrap
first commands loaded on the computer, checks hardware and loads firmware
interface
method where the user communicates with a computer
graphical user interface (GUI)
operating system that includes windows, icons, menus and pointers
command line interface
operating system where the user types commands
natural language interface
operating system that allows the user to type or speak commands
peripheral
hardware device, used to input, store or output data from a computer (that isnt part of the computer itself)
driver
program that controls a device like a printer or keyboard.
interrupt
a signal sent to the processor to tell it that its attention is required
interrupt service routine
program that retrieves an interrupt and performs required actions
high level language
programming language that uses english-like terms. considered portable
low level language
programming language that is closer to a machines language (either assembly or binary code)
portable
program that can be run on different types and manufacturers of computers
machine code
binary code, an example of low level language. non-portable
assembly language
low level language. code written in mnemonics that allows direct manipulation of the hardware. must be converted ton binary to be able to run
characteristics of high level language
- easier for users to understand, read and write
- easier for humans to debug
- portable, so machine independant
- MUST be converted to binary before it can run
- cannot directly manipulate hardware
characteristics of low level language
- more difficult for users to understand, read and write
- not portable so machine dependant
- harder for users to debug
- does not need converting, but must be assembled before execution (which is faster than conversion)
- can directly manipulate hardware
translator
software that converts code written in one programming language to another
assembler
converts assembly language into machine code
interpreter
translator that converts high level language into low level language by checking ONE LINE AT A TIME and executes it before checking the next (if the line checked is incorrect, an error is sent to the user)
compiler
translator that converts high level language into low level language by checking ALL code before running the program. (if any error is detected, they are reported to the user) an executable file is created if no errors are detected
executable file
file produced by compiler. can be run without conversion/translation and does not include source code
characteristics of interpreters
- translates one line of code at a time
- reports error as soon as its detected and stops program until its corrected
- useful when WRITING a program
- code needs to be re-translated each time its run
- source code is required to run the program
characteristics of compiler
- translates ALL line of code before executing the program
- reports errors at the same time (not as soon as its detected
- useful when program is FINISHED at needs to be tested
- produces executable file- doesnt require source code
IDE
software that allows a user to write, test and run program code. includes an editor so you can enter and amend your code. also includes a run-time environment
auto completion
feature of an editor that gives user options when they start typing a command
auto correction
feature of an editor identifies and corrects spelling errors
pretty print
feature of an editor that changes the colour of text (like highlighting key words)
run-time environment
feature of an IDE that allows program to run and lets user interact with the program
HTML
scripting language that is used to CREATE web pages
active script
used to produce any of the interactive elements of a web page
SSL protocol
encrypts data for transmission (invloved in HTTPS and HTTP)
session cookies
type of cookie that is deleted when the web browser is closed
persistent cookie
type of cookie that is stored by web browser until it is deleted by user or has expired
cookie
two types. store data regularly used on the internet
(like passwords, back details and online shopping carts)
crypto-currency
type of digital currency that uses encryption procedures
block chain
METHOD that is used to track all transactions made with a crypto-currency
digital ledger
database that is a LIST of all the transactions by the use of block chain
brute force attack
cyber threat that involves repeatedly inputting a password until the correct one is found
biometric password
type of password that uses a persons BIOlogical data (like a fingerprint)
packet sniffer
software used to examine contents of a data packet
DDoS
cyber threat that targets a web server to cause it to crash and prevent access to web pages it stores
botnet
bots created to perform a DDos attack
malware
type of malicious software that is downloaded onto a users device
proxy server
method of cyber security that examines requests sent by devices (to access web pages)
anti-malware
software that scans a computer with the purpose of finding and removing malware
fire wall
security method that is used to examine incoming and outgoing traffic from a network
trojan horse
cyber threat that is used to disguise other malware to sneak into a network
spyware
cyber threat that spies on a users action whilst using a computer such as copying key presses
adware
cyber tissue where advertisment automatically popup
ransomware
cyber threat (software-based) that encrypts users data to stop them from gaining access to it until money is paid
pharming
cyber threat that involves downloading malicious software onto a users hard drive. where a fake website asks a user to input personal details allowing it to be stolen.
phishing
cyber threat that involves sending a user a fake email that encourages the user to provide personal details.
social engineering
cyber threat that involves manipulating/deceiving a person to provide personal data
analogue
data that can be any value within a range
digital
limited data stored like 1’ and 0’
actuator
causes another device or part to move
expert system
attempts to replicate the knowledge of an expert . includes knowledge base, rule base and interface engine.
knowledge base
part of an expert system. stores facts
rule base
part of an expert system. stores the rules
interface engine
part of an expert system. makes the decision
