Chapter 1 - 4 and 7 key terms

IGCSE Computer Science (0478) Flashcards (2023+ exams)

binary

a base-2 number system that uses the values 0 and 1.

denary

a base-10 number system that uses the values 0-9.

digital

discrete data that is stored as Is and 0s.

digital data

discrete data that only uses the values 0 and 1.

hexadecimal

a base-16 number system that uses the values 0-9 and characters A-F.

two's complement

is the way most computers represent positive or negative integers. To get the two's complement negative notation of an integer, you write out the number in binary. You then invert the digits, and add one to the result.

analogue

continuous data that can be any value within a range.

analogue data

a continuous stream of data that is processed by humans.

ASCII

a code for representing English characters as numbers, with each letter assigned a number from 0 to 127

casting

converting data from one data type to another data type.

char

A single character, e.g. A', '1'.

character set

it contains all the characters that are in that chAiacter set and the binary value that is assigned to each character.

colour depth

the number of bits that arc used to create each colour in an image

metadata

additional data that is stored with an image that can provide information such as the dimensions of the image and the time and date the image was taken.

pixel

a very small dot of colour that is displayed with many other to create an image.

resolution

the dimensions of an image.

sample rate

the number of samples recorded each second.

sample resolution

the number of bits that are used to record each sound sample.

sound sampling

a little piece of sound that is recorded at regular time intervals.

unicode

A character code that enables most of the languages of the world to be symbolized with a special character identification.

bit

is the smallest unit of data in a computer. A bit has a single binary value, either 0 or 1.

byte

a unit of computer information or data-storage capacity that consists of a group of eight bits and is enough to represent one letter in ASCII

compression

a method that uses an algorithm to reduce the size of a file.

Exbibyte (EiB)

measure of computer storage: 1024 Pebibytes or 2^60 bytes

Gibibyte (GiB)

measure of computer storage: 1024 Mebibytes or 2^30 bytes

kibibyte (KiB)

measure of computer storage: 1024 bytes or 2^10 bytes.

lossless

a compression method that reduces the size of a file by temporarily altering the data.

lossy

a compression method that reduces the size of a file by permanently removing data.

Mebibyte (MiB)

measure of computer storage: 1024 Kibibytes or 2^20 bytes

Pebibyte (PiB)

measure of computer storage: 1024 Tebibytes or 2^50 bytes

perceptual music shaping

a process that is used in lossy compression that removes sounds that are not normally heard by the human ear.

run length encoding (RLE)

An algorithm that groups together repeating patterns and indexes them.

Tebibyte (TiB)

measure of computer storage: 1024 Gibibytes or 2^40 bytes

bandwidth

The maximum amount of data transmitted over an internet connection in a given amount of time.

ethernet

a system for connecting a number of devices to form a local area network. (Using cables)

full-duplex

a transmission method where data is transmitted in both directions at the same time.

half-duplex

a transmission method where is transmitted in both directions, but only one direction at a time.

internet

a very large global network that allows users to access the world wide web.

internet protocol (IP) address

the unique address that is given to a device when it is connected to a network.

latency

Latency is the time it takes for data to be transferred between its original source and its destination, measured in milliseconds. Internet latency and network latency affect satellite internet connections, cable internet connections, as well as some WiFi connections.

network

computers and devices that are joined together using cables or wireless technology.

packet

a small unit of data.

packet header

a section of a packet of data that contains information about the contents of the packet and its destination.

packet switching

a method of transmitting data packets across a network. Each data packet is able to take an individual pathway across the network.

payload

the actual data that the user is sending to the receiver.

router

a network component that examines a data packet to obtain its destination address and then forwards the packet to this address.

serial

a transmission method where data is sent one bit at a time down a single wire.

simplex

a transmission method where data is transmitted in a single direction only.

skew

Skew is a disadvantage of parallel transmission. Skew is caused by the fact that each wire in a parallel transmission setup will have slightly different properties. This will mean that each signal will travel at a slightly different speed therefore arriving at their destination at different times.

trailer

a section of a packet of data that contains information about any error checking methods that may be used.

USB

an industry standard that is used to transmit data.

USB cable

a type of transmission media that uses the USB method to transmit data.

USB connection

a collective name for using a USB cable plugged into a USB port to transfer data from one device to another.

USB device

the name of a device that plugs into a USB port on a computer.

USB port

a socket that is a part of a device or computer that enables you to insert a USB cable.

acknowledgement

a message that is sent from one device to another to indicate whether data is received correctly.

automatic repeat request (ARQ)

a type of error detection method that uses acknowledgement and timeout to see if data has arrived correctly after transmission.

check digit

a type of error detection method that is used for data entry. A calculation is performed on the data entered to create a value. Check digit values are compared to see if the data entered is correct.

checksum

a type of error detection method that performs a calculation on the data to create a checksum value. Checksum values arc compared after transmission to see if they match.

echo check

a type of error detection method that sends a copy of the transmitted data back to the sender to be compared with the original data sent.

interference

disruption, such as electromagnetism, to data when it is transmitted.

parity check

a type of error detection method that adds an additional bit to each byte to create an odd or even sum.

timeout

a period of time that is set and used to wait for an acknowledgement to be received.

two-step verification

a process that involves inputting two different kinds of data to enter an account or device.

type check

a type of validation that checks data is the correct data type.

visual check

comparing the data entered with the original side-by-side.

asymmetric

a type of encryption that uses two different keys to encrypt and decrypt data.

cipher text

the name given to data after transmission.

encryption

a method of securing data for storage or transmission that scrambles it and makes it meaningless, encryption key

parallel

a transmission method where data is sent multiple bits at a time down multiple wires.

plain text

the name given to data before encryption.

private key

This is the key that you should share with no one. If you encode with a private key anybody with the public key can decode. Your private key can be used to decode something encoded with your public key. (Part of asymmetric cryptography)

public key

It is part of asymmetric cryptography. This is the key that is shared. If you encode with the public key only the private key can decode. If someone encodes with a private key anybody with the public key can decode.

symmetric

a type of encryption that uses the same key to encrypt and decrypt data.

accumulator (ACC)

a register that is built into the ALU that stores the result of any interim calculations.

address

a memory location in RAM.

address bus

wires used for the transmission of addresses between components in a computer.

architecture

the design of a computer system, including the components it contains.

arithmetic logic unit (ALU)

the component in the CPU that performs all the mathematical and logical operations required when processing data and instructions.

automation

the use of automated equipment in a process, e.g. a factory.

cache

a type of storage that is built into the CPU, to store the most frequently used data and instructions.

central processing unit (CPU)

a component in a computer system that processes data and instructions.

clock speed

the number of fetch-decode-execute cycles that can be performed in a second.

control bus

wires used for the transmission of control signals between components in a computer.

control unit (CU)

the component in the CPU that controls all the operations in the CPU.

core

the part of the CPU that contains all the components that are used to perform the fetch-decode-execute cycle.

current instruction register (CIR)

a register that is built into the CU that holds the current instruction that is being processed in the CPU.

data bus

wires used for the transmission of data and instructions between components in a computer.

embedded system

a computer system that performs a dedicated function.

fetch-decode-execute cycle

the cycle through which data and instructions are processed.

instruction set

a set of commands that can be processed by a certain CPU.

Internet of Things

the connection of computer systems and everyday devices, using the Internet, to allow data to be exchanged.

memory address register (MAR)

a component in the CPU that stores the address of the next instruction to be processed

memory data register (MDR)

a component in the CPU that holds the data or instruction that arc fetched from RAM.

microprocessor

an integrated circuit that is able to perform many of the functions of a CPU.

program counter (PC)

a component in the CPU that stores the address of the next instruction to be processed.

programmable

a computer that will run the commands stored in it.

RAM (random access memory)

a component that holds data and programs that are currently in use.

register

a small component in a computer system that is used to temporarily store data.

Accelerometer sensor

This type of sensor measures acceleration forces. These may be static forces, such as the continual force of gravity. They can also be dynamic forces, such as those created by movement and vibrations.