Definitions Flashcards
Arithmetic Logic Unit (ALU)
Performs operations on data e.g. Addition and subtraction
Control Unit (CU)
Coordinating activities of the CPU
Registers
Quick and small stores of data within the CPU
Memory Address Register (MAR)
Holds memory address for data or a instruction about to be used by the CPU
Memory Data Register (MDR)
Holds actual data or instruction
Accumulator
Stores results of calculations in the ALU
Program Counter (PC)
Holds memory address of the instruction for each cycle
Fetch
The next instruction is retrieved by CPU from main memory
Decode
The instruction is broken down and decided so computer can understand
Execute
The CPU performs what the instructions told
Embedded System
A computer system built within a large device e.g. Camera/washer/car
Volatile
Memory loses its data when power of
Non-volatile
Memory retains its data when power is lost
Random Access Memory (RAM)
Read/write - function is to load open programs and operating system data currently in use - volatile
Read Only Memory (ROM)
Can only be read and can’t be changed - stores essential programs to be run in order to boot the computer - non-volatile
Cache
A type memory that stores copies of frequently used data - much faster than RAM - lower capacity - closer to CPU
Buses
Collection of wires that carry signals between various components of the computer system
Central Processing Unit (CPU)
Processes all of the data and instructions that make the system work - can be effected by clock speed/number of cores/cache size
Clock speed
How fast the computer does the FDE cycle
virtual memory
A memory management procedure needed when the RAM is full so a temporary section is made which acts like a part of RAM
Flash memory
Solid state storage - non-volatile - more reliable/durable but can only be overwritten a limited number of times
Graphics Processing Unit (GPU)
Handles graphics and image processing
Optical storage
CD - DVD - Blue-ray ADV: cheap - easy to transport DIS: slow - less storage than hard drives - stored data degrades over time - cannot be written over
Magnetic storage
Hard drives ADV: fast access - stores large amounts of data - low cost DIS: not very portable - easily be broken
Solid State storage
USB - flash memory - SD ADV: fast - small - light - easily portable - quiet DIS: more expensive - storage capacity less - limited number erase/write cycles
Cloud stotage
Data is stored on multiple servers in a remote location ADV: secure - can be accessed anywhere - no need to buy DIS: needs internet - download and upload can be effected by internet connection - less control if data is held
Operating System
essential software that links the hardware and other software together and generally manages the computer system
Command-line Interface
Text commands where user has to type in command
Graphical User Interface (GUI)
uses icons and other visual indicators to navigate and issue commands
Utility Software
maintains a computer
Defragmentation Software
reorganises data on the hard drive to put fragmented files back together and moves files to collect all the free space
Backup Software
Full Backup - a copy is taken from from every file on the system
Incremental Backup
only files created or edited since last backup are copied
Compression Software
reduces file size so they take up less space on hard disk
Encryption Software
scrambles data to stop others from accessing it
Open Source Software
source code is made freely available and users can modify it ADV: free - made for greater good - can be adapted DIS: small - buggy - security holes - no warranties - no customer support
Proprietary Software
only the compiled code is released and the source code is kept a secret ADV: warranties - well-tested - reliable - cheaper DIS: expensive - software may not fit user needs
Personal Area Network (PAN)
within the range of an individual person
Local Area Network (LAN)
a network that connects devices close to each other e.g. school and house
Wide Area Network (WAN)
a network within a large geographical area e.g. internet
Bandwidth
amount of data that can be transferred in a given time
Network Interface Card (NIC)
allow a device to connect to a network
Switch
connect devices on a LAN
Router
responsible for transmitting data between networks
Protocol
a set of standards/rules for connecting computers
Client-server Network
client has connection to server - servers can backup and store centrally but can be expensive and difficult to maintain
Peer-to-peer Network
no central server - each computer equal in responsibility - have to work as both server and a client.
Star Topology
ADV: better performance - rest of network not affected in one fails - simple to add more devices DIS: wire needed for all devices - expensive
Mesh Topology
ADV: faster DIS: expensive
MAC Address
assigned to all devices - unique to all devises and cannot be changed - permanent - identifies the actual device.
IP Adress
assigned either manually or automatic - the location of your device on the internet
Packet Switching
split data into packets to be sent across the network - each packet given a number order of data - each router reads packet header and decides which way to send it according to IP rules - packets then arrive and reassemble them in the right order.
TCP/IP
sets of rules for how devices connect on the network.
Hyper Text Transfer Protocol (HTTP)
used to access websites and communicate with web servers
HTTPS
more secure - encryption
File Transfer Protocol (FTP)
used to access - edit and move files between devices
Post Office Protocol (POP3)
used to retrieve emails from a server - holds until download - then deletes from server
Internet Message Access (IMAP)
used to retrieve emails - server holds until you actually delete it - only download a copy
Simple Mail Transfer Protocol (SMTP)
used to send emails - used to transfer emails between servers
Layer
ADV: manageable pieces - self-contained can change without effecting others
Application Layer
turning data into websites
Transport Layer
controlling data flow - splitting data into packets
Network Layer
making connections between networks
Data link Layer
passing data over physical network-
Domain Name Server (DNS)
translates websites’ domain name into its IP address
Virtual Network
network that is entirely software based - created by partitioning of some physical network
Blagging
invented scenario to engage a targeted victim in a manner that increases the chance the victim will divulge information
Phishing
used to gain personal information for purposes of identity theft - using fraudulent e-mail messages that appear to come from legitimate businesses.
Shouldering
used to obtain information such as personal identification numbers (PINs) and passwords and other confidential data by looking over the victim’s shoulder.
Malware
malicious software - computer programs designed to infiltrate and damage computers without the users consent.
Virus
program loaded onto a user’s computer without the user’s knowledge and performs malicious actions. It can self-replicate - inserting itself onto other programs or files - infecting them in the process.
Worm
program that replicates itself in order to spread to other computers. Often it uses a computer network to spread itself - relying on security failures on the target computer to access it.
Trojan Horse
program which misleads users of its true intent.
Spyware
aims to gather information about a person or organization without their knowledge
Adware
unwanted advertisements to the user of a computer
Brute Force Attack
trail and error to gain information
Denial of Service Attack (DOS)
hacker stop users from accessing a part of a network - flooding network with useless traffic making computer very slow
Data Interception And Theft
The unauthorized taking or interception of computer-based information. Data theft is the act of stealing computer-based information from an unknowing victim with the intent of compromising privacy or obtaining confidential information.
SQL Injection
sql
Zero-day Attack
before software is released it is tested as much as possible
Penetration Testing
organisations employ specialists to stimulate potential attacks on their network
Anti-malware Software
designed to find and stop malware from damaging a network
Encryption
data is translated into code which only someone with the correct key can access
Data Protection Act
your data should be protected and kept safe from hackers
Freedom of Information Act
allows members of the public to access information held by a public organisation
Computer Misuse Act
stop hacking and cyber crime - stop unauthorized access to private network
Copyright Act
protect intellectual property - anything someone has created
alphanumeric
collective name for letters/digits/symbols
analogue signal
a continuous signal which can’t be processed by a computer
argument
a value that a parameter of a subprogram actually takes
ALU
part of CPU that carries out arithmetic and Boolean operations
array
data structure where all data is stored and defined under one variable name
ASCII
A 7-bit character set consisting of 128 characters
assembler
a program that turns assembly language into machine code
assembly language
low-level langauge
authentication
a process for checking user identity
binary
a counting system using base-2 consisting of 0s and 1s
binary shift
moving the bits in a binary number left or right and filling gaps with 0s
BIOS
Basic Input Output System
bitmap image
a graphic made up of pixels
bit
a binary digit either 0 or 1
bit rate
number of bits used per second of sampled audio
breakpoint
a programming tool used to halt a program at a specific place
byte
8 bits
casting
a way of changing from one data type to another
character
a single alphanumeric symbol
code editor
part of an IDE where you write and edit your source code
colour depth
the number of bits used for each pixel in an image file
comment
a note added to source code to say what part of a program does
comparison operator
compares two values and outputs either true or false
compiled code
an executable file created by a compiler
compiler
a programming tool to translate source code into machine code
compression
process of making the size of a file smaller
computational thinking
tackling a problem through decomposition/abstraction/algorithmic thinking
concatenation
joining strings together
constant
named value which cannot be altered as program is running
debugging
identifying and fixing errors in a program
dedicated system
a computer system designed to carry out a specific task
denary
system using base-10
digital signal
the representation of an analogue signal using binary data
DO WHILE loop
type of iteration statement
erroneous data
test data that a program isn’t designed to accept
error diagnostics
information about an error once it is detected
extended ASCII
an 8-bit character set consisting of 256 characters
extreme data
Test data on the boundary of what a program will accept
field
A column of a database used to store a category of data
file handling
reading from and writing to external files
file sharing
copying files between services of work
final/terminal testing
when the testing stage of the software developing cycle is only done once to check the software.
flat-file database
A database that only contains one table of data
flow diagram
a graphical way of showing an algorithm
FOR loop
A type of count-controlled iteration statement
functionality testing
A type of testing that assesses how well a program meets the requirements
function
A sub program that takes parameters and returns a value
Gigabyte
1000 megabytes
global variable
a variable available throughout the whole program
GPU
A circuit for handling the processing of graphics and images
GUI
Allows the user to interact with the computer in a visual and intuitive way
GUI builder
an IDE tool for giving a program a graphical user interface
hexadecimal
a counting system using base-16 consisting of 0-9 digits and letters a-f
high-level language
A programming language like C++ or Java
IF statement
type of selection statement
indentation
Spaces put at the beginning of a line of code to help show a programs structure
input sanitization
removing unwanted characters from an input
input validation
Checking that an input meets a certain criteria
integer
A numerical data type for whole numbers
interpreter
A translator that turns source code into machine code
iteration statement
A statement which make a program repeat a series of instructions
iterative testing
Repeated testing done during the development of a program
kilobyte
1024 bytes
linker
a program tool which can combine codes
local variable
a variable that is only defined and useable within certain parts of a program
logic circuit
An electronic circuit for performing logic operations on binary data
logic error
when a program does something that was not intended
logic gate
an electronic circuit component that performs a Boolean operation
loop
A set of instructions that repeat until a condition is met
lossless compression
Temporarily removing a file to decrease file size
lossy compression
permanently removing a file to decrease file size
machine code
the lowest level of programming language formed of 1’s and 0’s
maintainability
a characteristic of a defensive design that helps programmers modify their creation
megabyte
1024 kilobytes
metadata
extra data stored in a file which gives information about the file’s properties
Bit
one binary number (1 or 0)
Nibble
4 bits
real (or float)
numbers that have a decimal part
Boolean
can only take one of two values (usually TRUE or FALSE)
string
used to represent text/collection of characters
decomposition
breaking a complex problem down into smaller problems and solving each one individually
abstraction
picking out important bits of information from the problem
algorithmic thinking
a logical way of getting from the problem to the solution
decisions
diamond boxes - flow diagram
start/stop
box with rounded corners - flow diagram
inputs/outputs
parallelogram - flow diagram
processes (instructions/calculations/processes)
rectangle - flow diagram
sub routine (reference other flow diagrams)
box with another boxes - flow diagram
sequences
only one way from start to finish
selections
multiple ways to get from start to finish
iterations
loops that allows to repeat a task
exponentiation
raise a number to a power
DIV operator
returns whole number part of division
MOD operator
returns remainder part of division
==
is equal to
<> or !=
is not equal to
is less than
>
is greater than
<=
is less than or equal to
> =
is greater than or equal to
comparison values
produce boolean value
x.upper
changes all characters in string x to upper case
x.lower
changes all characters in string x to lower case
x.length
returns number of character in string x
x[i]
extracts the character in position i from string x
x.subString(a[comma]b)
extracts string starting at portion a with length b from string x
switch-case statements
check value of a variable
for loops
example of a count-controlled loop
AND
&&
OR
|
NOT
!
element
each piece of data inside array
records
rows of tables in databases - store a category
fields
columns of tables in databases - story details about specific item
primary key
uniquely identifies record in table (database)
data values in same record
have different data types
data values in same field
have same data types
flat file database
only one table - viewed by opening one data file
relational database
combine flat-file databases - linked together by key fields
SQL definition
programming language used for creating, maintaining and accessing databases
SQL function
create/update/query databases - consists of standard commands called statements
Text - SQL data types
stores strings
Date - SQL data types
stores date in the form DD MM YYYY
Boolean - SQL data types
stores TRUE or FALSE
CREATE TABLE - SQL command
creates table with required number of fields
INSERT INTO - SQL command
adds records to table (complete records no specific field vs specific record assign field)
UPDATE-SET-WHERE - SQL command
updates record in database
SELECT - SQL command
tells database what information you want to achieve
FROM - SQL command
tells database which tables to look in
WHERE - SQL command
specifies condition that a record must satisfy before it is returned
WHERE with AND and OR - SQL command
makes search more specific
WHERE with LIKE - SQL command
searches for a pattern
LIKE - SQL command
% used to represent any combination of letters and numbers
ORDER BY - SQL command
sort records into ascending (ASC) or descending (DESC) order
parameters
special variables used to pass values into a sub program (specify name/data type/default value)
arguments
actual values that parameters take when sub program called
total number of colours
2^n (where n = number of bits per pixel)
24 bit colour depth
average device colour depth
resolution
density of the pixels in an image
bit rate equation
sampling frequency x sample size
range check - input validation
checks the data is within a specified range
presence check - input validation
checks data has been entered
check digit - input validation
checks numerical data has been entered accurately
format check - input validation
checks data has correct format
look-up table - input validation
checks data against a table of acceptable values
length check - input validation
checks data is correct length
syntax errors
rules or grammar of programming language is not followed so compiler or interpreter doesn’t understand
logic errors
when compiler or interpreter is able to run program but program does something unexpected
diagnosing logic errors
found through general use of program and by systematically testing
performance test
tests how quickly certain features run and their impact on computer resources
usability test
tests how user-friendly the interface and features are
security test
tests vulnerability to attacks and how securely data is stored
load/stress test
tests how it copes under extreme conditions
functionality test
tests if program meets initial requirements
software development cycle
requirements - design - implementation - testing - maintenance
normal data
data that user is likely to input
assemblers
turn assembly language into machine code
AND - Conjunction
e.g. A /\ B
OR - Disjunction
e.g. A\/B
NOT - Negation
e.g. -|A
What does SQL stand for?
Structured Query Language
What does SQL allow people to do?
Allows people to search for records that contain a particular item or items of data
procedure
a set of coded instructions that tell a computer how to run a program or calculation
translator
converts program code into machine code to be executed by the CPU
IDE
a software application that provides facilities to computer programmers for software development
Character set
List of binary codes that can be recognised by computers as being usable characters
Sampling frequency
Number of samples per second in a sound
Sample size
a measure of how many bits a sample contains which is directly a measure of quality
Ethernet
a wired way of connecting computers to a network
