slug
type
status
category
summary
date
tags
password
icon
Unit 1
Binary – base two number system based on the values 0 and 1 only.
Bit – abbreviation for binary digit.
One’s complement – each binary digit in a number is reversed to allow both negative and positive numbers to be represented.
Two’s complement – each binary digit is reversed and 1 is added in right-most position to produce another method of representing positive and negative numbers.
Sign and magnitude – binary number system where left-most bit is used to represent the sign (0 = + and 1 = –); the remaining bits represent the binary value.
Hexadecimal – a number system based on the value 16 (uses the denary digits 0 to 9 and the letters A to F).
Memory dump – contents of a computer memory output to screen or printer.
Binary-coded decimal (BCD) – number system that uses 4 bits to represent each denary digit.
ASCII code – coding system for all the characters on a keyboard and control codes.
Character set – a list of characters that have been defined by computer hardware and software. It is necessary to have a method of coding, so that the computer can understand human characters.
Unicode – coding system which represents all the languages of the world (first 128 characters are the same as ASCII code).
Unit 2
ARPAnet – Advanced Research Projects Agency Network.
WAN – wide area network (network covering a very large geographical area).
LAN – local area network (network covering a small area such as a single building).
MAN – metropolitan area network (network which is larger than a LAN but smaller than a WAN, which can cover several buildings in a single city, such as a university campus).
File server – a server on a network where central files and other data are stored. They can be accessed by a user logged onto the network.
Hub – hardware used to connect together a number of devices to form a LAN that directs incoming data packets to all devices on the network (LAN).
Switch – hardware used to connect together a number of devices to form a LAN that directs incoming data packets to a specific destination address only.
Router – device which enables data packets to be routed between different networks (for example, can join LANs to form a WAN).
Modem – modulator demodulator. A device that converts digital data to analogue data (to be sent down a telephone wire); conversely it also converts analogue data to digital data (which a computer can process).
WLAN – wireless LAN.
(W)AP – (Wireless) Access Point which allows a device to access a LAN without a wired connection.
PAN – network that is centred around a person or their workspace.
Client-server – network that uses separate dedicated servers and specific client workstations. All client computers are connected to the dedicated servers.
Spread spectrum technology – wideband radio frequency with a range of 30 to 50 metres.
Node – device connected to a network (it can be a computer, storage device or peripheral device).
Peer-to-peer – network in which each node can share its files with all the other nodes. Each node has its own data and there is no central server.
Thin client – device that needs access to the internet for it to work and depends on a more powerful computer for processing.
Thick client – device which can work both off line and on line and is able to do some processing even if not connected to a network/internet.
Bus network topology – network using single central cable in which all devices are connected to this cable so data can only travel in one direction and only one device is allowed to transmit at a time.
Packet – message/data sent over a network from node to node (packets include the address of the node sending the packet, the address of the packet recipient and the actual data – this is covered in greater depth in Chapter 14).
Star network topology – a network that uses a central hub/switch with all devices connected to this central hub/switch so all data packets are directed through this central hub/switch.
Mesh network topology – interlinked computers/devices, which use routing logic so data packets are sent from sending stations to receiving stations only by the shortest route.
Hybrid network – network made up of a combination of other network topologies.
Cloud storage – method of data storage where data is stored on off-site servers.
Data redundancy – situation in which the same data is stored on several servers in case of maintenance or repair.
Wi-Fi – wireless connectivity that uses radio waves, microwaves. Implements IEEE 802.11 protocols.
Bluetooth – wireless connectivity that uses radio waves in the 2.45 GHz frequency band.
Spread spectrum frequency hopping – a method of transmitting radio signals in which a device picks one of 79 channels at random. If the chosen channel is already in use, it randomly chooses another channel. It has a range up to 100 metres.
WPAN – wireless personal area network. A local wireless network which connects together devices in very close proximity (such as in a user’s house); typical devices would be a laptop, smartphone, tablet and printer.
Twisted pair cable – type of cable in which two wires of a single circuit are twisted together. Several twisted pairs make up a single cable.
Coaxial cable – cable made up of central copper core, insulation, copper mesh and outer insulation.
Fibre optic cable – cable made up of glass fibre wires which use pulses of light (rather than electricity) to transmit data.
Gateway – device that connects LANs which use different protocols.
Repeater – device used to boost a signal on both wired and wireless networks.
Repeating hubs – network devices which are a hybrid of hub and repeater unit.
Bridge – device that connects LANs which use the same protocols.
Soft modem – abbreviation for software modem; a software-based modem that uses minimal hardware.
NIC – network interface card. These cards allow devices to connect to a network/internet (usually associated with a MAC address set at the factory).
WNIC – wireless network interface cards/controllers.
Ethernet – protocol IEEE 802.3 used by many wired LANs.
Conflict – situation in which two devices have the same IP address. Broadcast – communication where pieces of data are sent from sender to receiver.
Collision – situation in which two messages/data from different sources are trying to transmit along the same data channel.
CSMA/CD – carrier sense multiple access with collision detection – a method used to detect collisions and resolve the issue.
Bit streaming – contiguous sequence of digital bits sent over a network/internet.
Buffering – store which holds data temporarily.
Bit rate – number of bits per second that can be transmitted over a network. It is a measure of the data transfer rate over a digital telecoms network.
On demand (bit streaming) – system that allows users to stream video or music files from a
central server as and when required without having to save the files on their own computer/ tablet/phone.
Real-time (bit streaming) – system in which an event is captured by camera (and microphone) connected to a computer and sent to a server where the data
is encoded. The user can access the data ‘as it happens’ live.
Unit 3
Memory cache – high speed memory external to processor which stores data which the processor will need again.
Random access memory (RAM) – primary memory unit that can be written to and read from.
Read-only memory (ROM) – primary memory unit that can only be read from.
Dynamic RAM (DRAM) – type of RAM chip that needs to be constantly refreshed.
Static RAM (SRAM) – type of RAM chip that uses flip-flops and does not need refreshing.
Refreshed – requirement to charge a component to retain its electronic state.
Programmable ROM (PROM) – type of ROM chip that can be programmed once.
Erasable PROM (EPROM) – type of ROM that can be programmed more than once using ultraviolet (UV) light.
Hard disk drive (HDD) – type of magnetic storage device that uses spinning disks.
Latency – the lag in a system; for example, the time to find a track on a hard disk, which depends on the time taken for the disk to rotate around to its read-write head.
Fragmented – storage of data in non-consecutive sectors; for example, due to editing and deletion of old data.
Removable hard disk drive – portable hard disk drive that is external to the computer; it can be connected via a USB part when required; often
used as a device to back up files and data.
Solid state drive (SSD) – storage media with no moving parts that relies on movement of electrons.
Electronically erasable programmable read-only memory (EEPROM) – read-only (ROM) chip that can be modified by the user, which can then be erased and written to repeatedly using pulsed voltages.
Flash memory – a type of EEPROM, particularly suited to use in drives such as SSDs, memory cards and memory sticks.
Optical storage – CDs, DVDs and Blu-rayTM discs that use laser light to read and write data.
Dual layering – used in DVDs; uses two recording layers.
Birefringence – a reading problem with DVDs caused by refraction of laser light into two beams.
Binder 3D printing – 3D printing method that uses a two-stage pass; the first stage uses dry powder and the second stage uses a binding agent. Direct 3D printing – 3D printing technique where print head moves in the x, y and z directions. Layers of melted material are built up using nozzles like an inkjet printer.
Digital to analogue converter (DAC) – needed to convert digital data into electric currents that can drive motors, actuators and relays, for example.
Analogue to digital converter (ADC) – needed to convert analogue data (read from sensors, for example) into a form understood by a computer. Organic LED (OLED) – uses movement of electrons between cathode and anode to produce an on-screen image. It generates its own light so no back lighting required.
Screen resolution – number of pixels in the horizontal and vertical directions on a television/computer screen.
Touch screen – screen on which the touch of a finger or stylus allows selection or manipulation of a screen image; they usually use capacitive
or resistive technology.
Capacitive – type of touch screen technology based on glass layers forming a capacitor, where fingers touching the screen cause a change in the electric field.
Resistive – type of touch screen technology. When a finger touches the screen, the glass layer touches the plastic layer, completing the circuit and causing a current to flow at that point.
Virtual reality headset – apparatus worn on the head that covers the eyes like a pair of goggles. It gives the user the ‘feeling of being there’ by immersing them totally in the virtual reality experience.
Sensor – input device that reads physical data from its surroundings.
Unit 4
Von Neumann architecture – computer architecture which introduced the concept of the stored program in the 1940s.
Arithmetic logic unit (ALU) – component in the processor which carries out all arithmetic and logical operations.
Control unit – ensures synchronisation of data flow and programs throughout the computer by sending out control signals along the control bus.
System clock – produces timing signals on the control bus to ensure synchronisation takes place.
Immediate access store (IAS) – holds all data and programs needed to be accessed by the control unit.
Accumulator – temporary general purpose register which stores numerical values at any part of a given operation.
Register – temporary component in the processor which can be general or specific in its use that holds data or instructions as part of the fetch- execute cycle.
Status register – used when an instruction requires some form of arithmetic or logical processing.
Flag – indicates the status of a bit in the status register, for example, N = 1 indicates the result of an addition gives a negative value.
Address bus – carries the addresses throughout the computer system.
Data bus – allows data to be carried from processor to memory (and vice versa) or to and from input/output devices.
Control bus – carries signals from control unit to all other computer components.
Unidirectional – used to describe a bus in which bits can travel in one direction only.
Bidirectional – used to describe a bus in which bits can travel in both directions.
Word – group of bits used by a computer to represent a single unit.
Clock cycle – clock speeds are measured in terms of GHz; this is the vibrational frequency of the clock which sends out pulses along the control bus – a 3.5 GHZ clock cycle means 3.5 billion clock cycles a second.
Overclocking – changing the clock speed of a system clock to a value higher than the factory/recommended setting.
BIOS – basic input/output system.
Cache memory – a high speed auxiliary memory which permits high speed data transfer and retrieval.
Core – a unit made up of ALU, control unit and registers which is part of a CPU. A CPU may contain a number of cores.
Dual core – a CPU containing two cores. Quad core – a CPU containing four cores.
Port – external connection to a computer which allows it to communicate with various peripheral devices. A number of different port technologies exist.
Universal Serial Bus (USB) – a type of port connecting devices to a computer.
Asynchronous serial data transmission – serial refers to a single wire being used to transmit bits of data one after the other. Asynchronous refers to a sender using its own clock/timer device rather sharing the same clock/timer with the recipient device.
High-definition multimedia interface (HDMI) – type of port connecting devices to a computer.
Video Graphics Array (VGA) – type of port connecting devices to a computer.
High-bandwidth digital copy protection (HDCP) – part of HDMI
technology which reduces risk of piracy of software and multimedia.
Fetch-execute cycle – a cycle in which instructions and data are fetched from memory and then decoded and finally executed.
Program counter (PC) – a register used in a computer to store the address of the instruction which is currently being executed.
Current instruction register – a register used to contain the instruction which is currently being executed or decoded.
Register Transfer Notation (RTN) – short hand notation to show movement of data and instructions in a processor, can be used to represent the operation of the fetch-execute cycle.
Interrupt – signal sent from a device or software to
a processor requesting its attention; the processor suspends all operations until the interrupt has been serviced.
Interrupt priority – all interrupts are given a priority so that the processor knows which need to be serviced first and which interrupts are to be dealt with quickly.
Interrupt service routine (ISR) or interrupt handler – software which handles interrupt requests (such as
‘printer out of paper’) and sends the request to the CPU for processing.
Unit 5
CMOS – complementary metal-oxide semiconductor.
Operating system – software that provides an environment in which applications can run and provides an interface between hardware and human operators.
HCI – human–computer interface.
GUI – graphical user interface.
CLI – command line interface.
Icon – small picture or symbol used to represent, for example, an application on a screen.
WIMP – windows, icons, menu and pointing device.
Post-WIMP – interfaces that go beyond WIMP and use touch screen technology rather than a pointing device.
Pinching and rotating – actions by fingers on a touch screen to carry out tasks such as move, enlarge, reduce, and so on.
Memory management – part of the operating system that controls the main memory.
Memory optimization –function of memory management that determines how memory is allocated and deallocated.
Memory organization –function of memory management that determines how much memory is allocated to an application.
Security management – part of the operating system that ensures the integrity, confidentiality and availability of data.
Contiguous – items next to each other.
Virtual memory systems – memory management (part of OS) that makes use of hardware and software to enable a computer to compensate for shortage of actual physical memory.
Memory protection – function of memory management that ensures two competing applications cannot use same memory locations at the same time.
Process management – part of the operating system that involves allocation of resources and permits the sharing and exchange of data.
Hardware management – part of the operating system that controls all input/output devices connected to a computer (made up of sub-management systems such as printer management, secondary storage management, and so on).
Device driver – software that communicates with the operating system and translates data into a format understood by the device.
Utility program – parts of the operating system which carry out certain functions, such as virus checking, defragmentation or hard disk formatting.
Disk formatter – utility that prepares a disk to allow data/files to be stored and retrieved.
Bad sector – a faulty sector on an HDD which can be soft or hard.
Antivirus software – software that quarantines and deletes files or programs infected by a virus (or other malware). It can be run in the background or initiated by the user.
Heuristic checking – checking of software for behaviour that could indicate a possible virus.
Quarantine – file or program identified as being infected by a virus which has been isolated by antivirus software before it is deleted at a later stage.
False positive – a file or program identified by a virus checker as being infected but the user knows this cannot be correct.
Disk defragmenter – utility that reorganises the sectors on a hard disk so that files can be stored in contiguous data blocks.
Disk content analysis software – utility that checks disk drives for empty space and disk usage by reviewing files and folders.
Disk compression – software that compresses data before storage on an HDD.
Back-up utility – software that makes copies of files on another portable storage device.
Program library – a library on a computer where programs and routines are stored which can be freely accessed by other software developers for use in their own programs.
Library program – a program stored in a library for future use by other programmers.
Library routine – a tested and ready-to-use routine available in the development system of a programming language that can be incorporated into a program.
Dynamic link file (DLL) – a library routine that can be linked to another program only at the run time stage.
Unit 6
Data privacy – the privacy of personal information, or other information stored on a computer, that should not be accessed by unauthorised parties.
Data protection laws – laws which govern how data should be kept private and secure.
Data security – methods taken to prevent unauthorised access to data and to recover data if lost or corrupted.
User account – an agreement that allows an individual to use a computer or network server, often requiring a user name and password. Authentication – a way of proving somebody or something is who or what they claim to be.
Access rights (data security) – use of access levels to ensure only authorised users can gain access to certain data.
Malware –malicious software that seeks to damage or gain unauthorised access to a computer system.
Firewall – software or hardware that sits between
a computer and external network that monitors and filters all incoming and outgoing activities.
Anti-spyware software – software that detects and removes spyware programs installed illegally on a user’s computer system.
Encryption – the use of encryption keys to make data meaningless without the correct decryption key.
Biometrics – use of unique human characteristics to identify a user
(such as fingerprints or face recognition).
Hacking – illegal access to a computer system without the owner’s permission.
Malicious hacking – hacking done with the sole intent of causing harm to a computer system or user (for example, deletion of files or use of private data to the hacker’s advantage).
Ethical hacking – hacking used to test the security and vulnerability of a computer system. The hacking is carried out with the permission of the computer system owner, for example, to help a company identify risks associated with malicious hacking of their computer systems.
Phishing – legitimate-looking emails designed to trick a recipient into giving their personal data to the sender of the email.
Pharming – redirecting a user to a fake website in order to illegally obtain personal data about the user.
DNS cache poisoning – altering IP addresses on a DNS server by a ‘pharmer’ or hacker with the intention of redirecting a user to their fake website.
Unit 7
Legal – relating to, or permissible by, law.
Morality – an understanding of the difference between right and wrong, often founded in personal beliefs.
Ethics – moral principles governing an individual’s or organisation’s behaviour, such as a code of conduct.
Culture – the attitudes, values and practices shared by a group of people/society.
Intellectual property rights – rules governing an individual’s ownership of their own creations or ideas, prohibiting the copying of, for example, software without the owner’s permission.
Privacy – the right to keep personal information and data secret and for it to not be unwillingly accessed or shared through, for example, hacking.
Plagiarism – the act of taking another person’s work and claiming it as one’s own.
BCS – British Computer Society.
IEEE – Institute of Electrical and Electronics Engineers.
ACM – Association for Computing Machinery.
Unit 8
Database – a structured collection of items of data that can be accessed by different applications programs.
Relational database – a database where the data items are linked by internal pointers.
Table – a group of similar data, in a database, with rows for each instance of an entity and columns for each attribute.
Record (database) – a row in a table in a database. Field – a column in a table in a database.
Tuple – one instance of an entity, which is represented by a row in a table.
Entity – anything that can have data stored about it, for example, a person, place, event, thing.
Attribute (database) – an individual data item stored for an entity, for example, for a person, attributes could include name, address, date of birth.
Candidate key – an attribute or smallest set of attributes in a table where no tuple has the same value.
Primary key – a unique identifier for a table. It is a special case of a candidate key.
Secondary key – a candidate key that is an alternative to the primary key.
Foreign key – a set of attributes in one table that refer to the primary key in another table.
Relationship – situation in which one table in a database has a foreign key that refers to a primary key in another table in the database.
Referential integrity – property of a database that does not contain any values of a foreign key that are not matched to the corresponding primary key.
Index (database) – a data structure built from one or more columns in a database table to speed up searching for data.
Entity-relationship (E-R) model or E-R diagram – a graphical representation of a database and the relationships between the entities.
Normalisation (database) – the process of organising data to be stored in a database into two or more tables and relationships between the tables, so that data redundancy is minimised.
First normal form (1NF) – the status of a relational database in which entities do not contain repeated groups of attributes.
Second normal form (2NF) – the status of a relational database in which entities are in 1NF and any non-key attributes depend upon the primary key.
Third normal form (3NF) – the status of a relational database in which entities are in 2NF and all non-key attributes are independent.
Composite key – a set of attributes that form a primary key to provide a unique identifier for a table.
Unit 9
Abstraction – the process of extracting information that is essential, while ignoring what is not relevant, for the provision of a solution.
Decomposition – the process of breaking a complex problem into smaller parts.
Pattern recognition – the identification of parts of a problem that are similar and could use the same solution.
Unit 10
Data type – a classification attributed to an item of data, which determines the types of value it can take and how it can be used.
Identifier – a unique name applied to an item of data.
Record (data type) – a composite data type comprising several related items that may be of different data types.
Composite data type – a data type constructed using several of the basic data types available in a particular programming language.
Array – a data structure containing several elements of the same data type.
Index (array) – a numerical indicator of an item of data’s position in an array.
Lower bound – the index of the first element in an array, usually 0 or 1.
Upper bound – the index of the last element in an array.
Linear search – a method of searching in which each element of an array is checked in order.
Bubble sort – a method of sorting data in an array into alphabetical or numerical order by comparing adjacent items and swapping them if they are in the wrong order.
File – a collection of data stored by a computer program to be used again.
Abstract data type (ADT) – a collection of data and a set of operations on that data.
Stack – a list containing several items operating on the last in, first out (LIFO) principle.
Queue – a list containing several items operating on the first in, first out (FIFO) principle.
Linked list – a list containing several items in which each item in the list points to the next item in the list.
Unit 11
Constant – a named value that cannot change during the execution of a program.
Variable – a named value that can change during the execution of a program.
Function – a set of statements that can be grouped together and easily called in a program whenever required, rather than repeating all of the statements each time. Unlike a procedure, a function always returns a value.
Library routine – a tested and ready-to-use routine available in the development system of a programming language that can be incorporated into a program.
Procedure – a set of statements that can be grouped together and easily called in a program whenever required, rather than repeating all of the statements each time.
Unit 12
Program development lifecycle – the process of developing a program set out in five stages: analysis, design, coding, testing and maintenance.
Analysis – part of the program development lifecycle; a process of investigation, leading to the specification of what a program is required to do.
Design – part of the program development lifecycle; it uses the program specification from the analysis stage to show how the program should be developed.
Coding – part of the program development lifecycle; the writing of the program or suite of programs.
Testing – part of the program development lifecycle; the testing of the program to make sure that it works under all conditions.
Maintenance – part of the program development lifecycle; the process of making sure that the program continues to work during use.
Waterfall model – a linear sequential program development cycle, in which each stage is completed before the next is begun.
Iterative model – a type of program development cycle in which a simple subset of the requirements is developed, then expanded or enhanced, with the development cycle being repeated until the full system has been developed.
Rapid application development (RAD) – a type of program development cycle in which different parts of the requirements are developed in parallel, using prototyping to provide early user involvement in testing.
- 作者:现代数学启蒙
- 链接:https://www.math1234567.com/article/bookvoca
- 声明:本文采用 CC BY-NC-SA 4.0 许可协议,转载请注明出处。
相关文章