Computer Science

• MAC address


  Every NIC has a unique numeric MAC (Media Access Control) address assigned to it by its manufacturer so it can be identified. This is a 48 bit number, usually written as 12 hex digits
• Packets


  The unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. It consists of data with a header containing additional addressing and sequencing information. A longer message can be split up into many packets
• Router


  A device designed to connect multiple networks together. It passes packets on to another routers as they make their way to their destination address. It can also be used as the link between a LAN and the Internet
• Switch


  A component of a single (usually large) LAN that knows the MAC addresses of each device connected to it locally, so it can forward inbound packets to the correct recipient
• Ethernet


  The traditional technology for connecting wired LANs, enabling devices to communicate with each other with specific Ethernet protocols (a set of rules) to control the passing of information. An Ethernet cable is the physical, encased wiring over which the data travels
• Wireless Access Points (WAPs)

  A transmitter that receives data (packets) from a network via its physical connection, and then converts them into radio waves which are transmitted to receiving devices with WiFi adaptors
• Encryption


  The process of converting information or data into a code, especially to prevent unauthorized access
• Client-Server network


  Made up of ordinary computers (Clients) and more powerful specialist computers (Servers) which provide various resources, such as printing, storage and web access
• Peer-to-peer network


  One in which two or more PCs share files and access to devices such as printers without requiring a separate server. They are fairly simply wired together
• Hosting


  The process by which a company (such as an Internet Service Provider like BT) is able to store your files (such as webpages, images, video etc) and make them available on the World Wide Web
• Wireless Access Point (WAP)


  A transmitter that receives data (packets) from a network via its physical connection, and then converts them into radio waves which are transmitted to receiving devices with WiFi adaptors
• Peer-to-peer network


  • Two or more PCs share files and access to devices such as printers without requiring a separate server, fairly simply wired together
• Hosting


  The process by which a company (such as an Internet Service Provider like BT) is able to store your files (such as webpages, images, video etc) and make them available on the Internet
• Protocols


  • Ethernet
  • FTP
  • TCP/IP
  • HTTPS
  • POP
  • IMAP
  • SMTP
• Network Layers


  • The TCP/IP model consists of four layers: Application, Transport, Network, Link
• Malware


  Software that is specifically designed to disrupt, damage, or gain unauthorized access to a computer system, including viruses, spyware, worms, trojans and ransomware
• Brute Force Attack


  The simplest method to gain access to a site or server that is password protected, trying various combinations of usernames and passwords again and again until it gets in
• Denial of Service (DoS)

  An attempt to prevent legitimate users from accessing a website, often done by flooding a company's network with useless traffic
• Network Forensics


  Processes where a network is monitored to reveal who has communicated with whom, when, how, and how often
• Penetration Testing


  Used to find any security weaknesses in a system by attempting to break into it
• Acceptable Use Policy


  An organisation's policy which makes it clear to all network users what is acceptable and what is not
• Firewall


  • Designed to prevent unauthorised access to or from a computer or private network that is connected to the Internet, examines each packet and blocks those which do not meet specified security criteria
• Access Levels


  • Part of an access control procedure for computer systems, allows a system administrator to set up a hierarchy of password protected users, low level users can access only a limited set of information, highest level users can access the most sensitive data
• Operating System


  A group of programs that manage the computer's resources, provides the User Interface, Memory management, Multi-programming and Peripheral management as well as file and user management
• User Interface


  The means by which the user can communicate with a computer (eg. Command-line Interface, Menu system or Graphical User Interface such as a WIMP system: Windows, Icons, menus, pointers)
• Utility Software


  Useful programs that often are part of the Operating System but are not essential to it, examples include Encryption utilities, Data Compression utilities, Disc Defragmentation utilities, Backup utilities
• Backup


  A copy of all the user's files, which can be restored in the event of files getting corrupted or deleted
• Abstraction


  A key concept in computational thinking which involves removing unnecessary detail from a problem in order to solve it more easily, the classic Underground map is a good example
• Simulation


  A computer model of a problem, which will show what happens under different circumstances, examples are financial models, meteorological models and game simulations
• Decomposition


  Involves the breaking down of a problem into smaller, simpler steps or stages
• Program Maintenance


  Updating and modifying programs with time in the light of experience or changing circumstances, to make this easier programmers should use comments, meaningful variable names, indentation and subroutines
• Syntax errors


  Where the language rules are broken, the program will not run
• Logical errors


  Errors in the logic of a program, the program will run but produce incorrect results
• Invalid Data


  Test data that is of the correct data type, but is out of range
• Erroneous Data


  Test data of the incorrect data type
• Iterative Testing


  Where the programmer tests the program as it is being developed and corrects any resulting errors
• Final Testing


  Carried out by different people to the programmers, either Testers or Users, checks that the final program is complete, correct and has all desired functions
• Variable


  A memory location represented by a name in a computer program whose stored value is allowed to change
• Identifier


  A unique name that refers to a location in memory where a data item will be stored
• Data Type


  A classification that specifies which type of value a variable has and what type of mathematical, relational or logical operations can be applied to it without causing an error, examples are string and integer