Computer Science Flashcards
abstraction
the process of removing unnecessary details so that only the main, important points remain
address
a number assigned to the storage location so that it can be accessed
adjacent items
items of data that are next to each other
alpha testing
testing done by the programmer
analogue
data which can use any value in a continuous range
antivirus software
software designed to prevent, detect and remove malware
applet
a small application or program created in the Java programming language that can be sent to a user along with the web page they have requested (e.g. applets of animations, word processors and games)
application software
are end-user programs. Also called ‘apps’ or ‘applications’, they are written to be run by users to perform user-identified tasks. For example, for productivity or entertainment. They include word processor, spreadsheet, database, game and image editing software
argument
the name for the data that is passed to a subroutine by the main program
array
a structure that contains many items of data of the same type. The data are indexed so that a particular item of data can be easily found
assembler
a program which translates assembly language into machine code
assigning
giving a variable a value
authenticate
confirm that a user’s password has been entered correctly
authentication
the process of determining whether someone trying to log into the network is who they declare to be
autonomous
the ability to act on their own without human input
bandwidth
the amount of data that can pass through the transmission medium per second. It is often called the bit-rate
base 2
a base 2 number system represents numbers using two different symbols. Each place value is two times bigger than the place to its right
base 10
a base 10 number system represents numbers using ten different symbols. Each place value is ten times bigger than the place to its right
beta testing
testing done by a selected group of individuals to receive their feedback about how well the program works
bitmap image
A set of bits that represents a graphic image, with each bit or group of bits corresponding to a pixel in the image.
binary digits
computers can only communicate directly in 0s and 1s; series of 0s and 1s represent the codes for various instructions and data
binary tree
items of data are stored in leaves and the branch points are called internal nodes. In a binary tree, each node has at most two branches or children
biometric authentication
a process that validates the identity of a user who wishes to sign into a system by measuring some unique, physical characteristic of that user such as fingerprints, eye scans, face recognition and voice prints
BIOS
the Basic Input/Output System controls the computer when it is first switched on
bot
(also known as an internet bot or WWW bot) is software that runs repetitive automated tasks over the internet
boundary test
where the highest or lowest acceptable numbers and those just inside or outside the acceptable range are entered; these check any logical errors that might have been introduced using the = operators
bus
a bundle of wires carrying data from one component to another or a number of tracks on a printed circuit board fulfilling the same function
byte
a group of eight bits
cables
a way of connecting computers using cables and sockets
cache
a temporary data store so that the data can be accessed very quickly when needed
called
subroutines are ‘called’ by the main program: this means that they are started up, given data, run and then the output is collected by the main program (if required)
casting
converting one data type to another data type
central processing unit
this is the component of the computer that controls the other devices, executes the instructions and processes the data
character
often abbreviated to ‘char’, it is a variable that holds one letter, number or symbol
character set
the list of binary codes that can be recognised by computers as being usable characters
closed
when the computer has finished using the file, closing it saves it safely on to the disk for permanent retention
colour depth
the number of bits used to encode the colour of each pixel
comment
a piece of information for the programmer. It does not form part of the program and is not executed by the computer. It is for information only
compare
assess how items of data are similar or different to each other, to help decide which order they should go in
compiler
a program that converts high-level programs into low-level programs
compound statement
a statement where Boolean operators are combined and work together to examine if several conditions are true or false
compression
reducing the size of a file so that it takes up less storage space or bandwidth when it is transmitted
concatenation
the placing together of two separate objects so that they can be treated as one, for example a string variable can be joined end-to-end to produce a larger string
constant
a value that does not change while the program is running
control signals
electrical signals that are sent out to all of the devices to check their status and give them instructions
copyright
the legal right of the person who created a work to use that work exclusively or to grant permission to others to use it
cracking
gaining unauthorised access to computer systems, often on a network, by bypassing internet security systems with the intent of committing a crime or with malicious intent
cyber security
the use of technology, working practices and precautions designed to protect networks, computers, programs and data from attack, damage or unauthorised access
decision
when a question is asked (as in selection) the answer will lead to one or more varied alternative actions
decomposition
breaking a problem down into smaller, more manageable parts which are then easier to solve
domain name
this is part of the URL for a resource on the internet. When the domain name is used, it will be converted to the correct IP address by the Domain Name Service (DNS) and the contact will take place
driver
a program called by a peripheral manager to operate any device, for example printers, the screen and mouse, when they are called by the main program
dry run
the program is run on paper and each stage is carefully analysed to see what values the various variables, inputs and outputs have. At this stage, a computer is not being used
dynamic array
an array that has not had its size defined and can change as data are appended
efficiency
efficiency can be assessed by: How long it takes a program to generate a result. How much code has been written to generate the result. How much memory it uses
electrical storage
storing data using devices such as flash memory. This is sometimes called ‘solid state’
entity
something recognised as being capable of an independent existence, which can be uniquely identified, and about which data can be stored. It can be a physical object, for example a car, person, student or book. It can also be a concept, for example a customer transaction
erroneous test
data that should be rejected are deliberately input to check that validation routines are functioning as expected (sometimes called an ‘out-of-range test’)
Ethernet
a set of rules or protocols for computers to follow when communicating data over a network
ethics
a system of moral principles, often shown by doing things that society recognises as being good or by acting in ways that individuals and societies believe reflects good values
execute
to run a computer program or process
execution
when a program or part of a program is run by the computer
field
one item of information. For example, the make, model and maximum speed of a car are all fields
file handle
a label that is assigned to a resource needed by the program. It can only access the file through the computer’s operating system
flash memory
this is memory which can be programmed electrically but then keeps its data when the power is turned off
frequency
the number of waves produced per second
global variable
a variable that is used in the main program. It can be used by any of the commands or subroutines in the program
hacking
the unauthorised access to a computer system and the data it contains
hardware
the physical components making up the computer and its peripheral devices
heat sink
a metal device, glued to the CPU chip with thermally conducting paste, to transfer the heat away from the chip
HTML
hypertext markup language (HTML) is used to write web pages for the internet as well as for ebooks, PDF documents, etc.
identifier
the ‘name’ given to a variable
index
a number that identifies each element of an array or string
input sanitisation
when any inputs from users that could be harmful to its systems are filtered out and removed
instruction
an instruction to a microprocessor to perform a specific task
instruction set
the set of instructions for a particular processor which it will understand and be able to process
integer
a whole number without decimals (can be positive or negative)
interpreter
a program which will run a high-level program directly, interpreting the instructions and converting them, without them needing to be in the machine code of a computer
IP address
a unique software address used to communicate over the internet
iteration
a procedure or a set of statements or commands is repeated either for a set number of times or until there is a desired outcome
legal
abiding by the laws and rules of a particular country or jurisdiction
local area network
network used for data transmission by computing devices within one building or site, such as an office building, a school or university campus. It is usually owned and managed by a single organisation, for example a school or business
local variable
a variable that is used only within a subroutine. When the subroutine has completed its work, the local variable is discarded
logic circuit
a combination of standard logic gates used to perform complex logic operations where the outputs of some gates act as the inputs to others
logical error
a problem in the design of the algorithm
logic gate
an electronic component that either produces or does not produce an output depending on the inputs it receives and the logic rule it is designed to apply
logical operator
operators such as ‘AND’, ‘OR’ and ‘NOT’ that perform a Boolean operation on some inputs
loop
part of a program where the same activity is repeated over and over again for a fixed number of times or until a condition is met. Usually the condition is stated within the loop itself
lossless compression
lossless compression: no data are lost and the file can be decompressed with all of its information intact
lossy compression
data are lost in the compression process and when the file is decompressed it will not contain all of the original material
low-level language
a computer language that provides instructions that are the same as or very similar to a computer’s instruction set
machine code
the instructions in a form that the processor can execute; strings of 0s and 1s
magnetic storage
storing data using magnetic media such as a hard disk drive
main memory
the physical memory that is internal to the computer. The word ‘main’ is used to distinguish it from storage devices such as hard disk drives. It can be directly accessed by the CPU
malware
software designed to gain unauthorised access to a computer system in order to disrupt its functioning or collect information without the user’s knowledge
menu
a set of options to help a user find information or use a program function
microwaves
electromagnetic waves which can be used to carry data between computers
mnemonic
a tool or technique designed to help a person’s memory (e.g. ‘Richard of York gave battle in vain’ used to help remember the order of the colours of the spectrum: red, orange, yellow, green, blue, indigo and violet)
modem
short for ‘modulatordemodulator’; modulates and demodulates signals (converts them from digital to analogue and vice versa) sent from and received by a computer over a communications network
motherboard
the main printed circuit board of the computer; it has connectors that other circuit boards can be slotted into
multitasking
when a computer is running several programs at the same time
nibble
half a byte or 4 bits
node
places on the network where there are items of equipment
normal test
ensures that the correct result will be produced with the expected data (sometimes called an ‘in-range test’)
opcode
the code for the instruction being given
operand
the data that might be attached to the opcode and that the instruction might need to work with
operator
the symbol that tells the computer what to do
optical storage
storing data using optical devices such as CDs and DVDs
ordered
the data in the list are stored in order
overflow error
when a calculation produces a result that is greater than the computer can deal with or store in the available number of bits
overwritten
if a file exists on the computer and a new file is created with the same name, the new file is kept and the old file is written over and lost
packet
a small block of data that is transmitted from one computer to another
packet switching
a method of data transmission in which a message is broken into a number of parts which are sent independently over the most suitable routes. The message is reassembled at the destination
parallel processing
when the processor cores work on different parts of the same program
parameter
the names of the variables that are used in the subroutine to store the data passed from the main program as arguments
parentheses
brackets
patch
software designed to update a computer program in order to fix or improve it
patent
a permission granted by a government to a person for a set period of time to stop other people from making use of their inventions without their permission
penetration test
tests a computer system or network to find vulnerabilities that an attacker could exploit
permission
a rule that is set up for a particular file to control who can edit, read or write on the file
personal area network
network used for data transmission over short distances by devices such as laptops, mobile phones, tablets, media players, speakers and printers
pixel
the smallest possible dot on a computer screen which can have its colour set independently; images are made up of pixels
place value
the value that a digit’s position in a number gives it, for example (for decimal) in the number 356, the digit 5 has a value of 50 whereas in the number 3560, the digit 5 has a value of 500
printed circuit board
the base that supports the wiring and electronic components that are soldered to it or fit into sockets on the board
process
an activity that a computer program is performing
property
one of the characteristics of attributes of a data type, for example one of the properties of a string variable is its length, that is the number of characters it contains
protocols
agreed rules for requesting and sending data across networks
pseudo-code
a language that is similar to a real programming language but is easier for humans to use and understand when they are developing algorithms. Although it doesn’t actually run on a computer it can easily be converted to a regular programming language
RAM
(also known as random access memory) memory that can be used by computer programs to store data and instructions, but all of its data is lost when the computer is switched off
read mode
the file is opened in such a way as to allow the data to be used by the program but not to allow the program to write any data to the file. Using read mode protects the data file from being accidentally changed by the program
real
a numeric variable which can have a fractional value; it can have digits on either side of a decimal point. Commonly used to store currency values, for example 1.5 for £1.50
redundancy
the number of items of data in a file which are repeated
register
a storage location that is inside the CPU itself
Regulation of Investigatory Powers Act 2000
this is a law that regulates the behaviour of officers who are investigating crime; it covers surveillance, listening to phone calls, obtaining information from internet service providers, mobile phone providers etc.
relational operator
an operator which compares two items of data, for example , =
resolution
the number of pixels per square inch on the computer screen. The higher the resolution, the better the picture
run
a sequence of repeated characters, for example: aaaa
sampling
making physical measurements of the amplitude of an electronic representation of the sound wave at set time intervals and then converting the measurements to digital values
searching
looking through a file to see if particular data are there
secondary storage devices
devices that store information but which do not lose the data when they are switched off; usually not on the main circuit board (motherboard)
selection
a question is asked, and depending on the answer, the algorithm takes one of two courses of action
sequence
the order in which tasks are carried out
sequential
starts at the beginning and moves through the list one-by-one
social engineering
psychologically tricking people into divulging their secret information or doing things that they would not otherwise do
sorting
putting items of data into a precise order, for example alphabetical or numerical
static array
an array that is of a set size
storage location
a place in RAM where a single piece of data can be kept until it is needed
string traversal
moving through a string, one piece of data at a time; sometimes this might just mean counting
subroutine
a self-contained piece of code that can be ‘called’ by the main program when it is needed
substring
a smaller string which is part of the main string that you are using
sub-tasks
small steps making up a larger task
syntax
the rules of spelling, punctuation and grammar of a language so that the meaning of what is being communicated is clear (humans can make allowances if the rules are broken, but computers can’t!)
syntax error
a grammatical mistake in the code. For example, it could be caused by a misspelling, e.g. ‘prnit’ instead of ‘print’ or by missing colons, semi-colons or brackets
systems development cycle
a defined process of planning, designing, creating, testing and deploying an information system
system software
software that manages the operation of the computer, tells it what to do, tells it which programs to run, controls what the users see on screen etc.
table
a collection of rows and columns forming cells which is used to store data and user information in a structured and organised manner
test data
carefully planned sample data, used to try out programs to check that they give the correct outputs
testing plan
a plan for the way in which a program is to be tested
trace table
while a dry run is being worked through, a table is drawn up showing the values of each variable, input and output, and how they change as the program is running. A trace table has columns for each of the variables and rows for each of the steps in the algorithm
topology
the structure of the network
traverse
go through a loop item by item
Trojan horse
a phrase used to describe unintentionally accepting a hidden enemy attack; from an ancient Greek myth where, a large wooden horse (in which enemy soldiers were hidden) was left a a gift for the city of Troy, and the people took it into the city, sealing their fate
true or false
indicates whether a logical statement is correct or incorrect; this could be represented in a computer as 1s (true statements) and 0s (false statements)
truth table
a table that shows all the possible combinations of outputs which can occur with all of the different possible inputs; usually used with logic problems
user interface
the way in which a user interacts with a computer system
unambiguous
this means that the instruction cannot be misunderstood and the correct action will always be performed. All instructions given to a computer must be unambiguous or it won’t do anything!
validation
the process through which the program checks that data are sensible and that they are suitable for use by the program
variable
a container which is used to store values such as an ‘attempts’ counter
volatile
data are permanently lost when power is switched off
wearable technology
includes clothing or electronic devices that can be carried or attached to the body
wide area network
a network connecting local area networks over a large geographical area
Wi-Fi
consists of the protocols needed for communication over a wireless network. It is the wireless version of a wired Ethernet protocols
write mode
the program can ‘write’ to the file or in other words it can change the data in the file
