IB Computer Science HL

System

An organised and purposeful structure that consists of interrelated and interdependent elements. All systems have inputs, processes and outputs.

User roles

The roles which workers have in a system. Normally used when evaluating the context in which a new system is being installed.

Change management

The approach taken to deal with the different externalities due to the change of a system in an organization.

Compatibility issues

This occurs when data cannot be processed in different computers due to different data types, formats or algorithms.

Legacy system

An outdated computer system which often requires a change.

Business merger

When two organisations decide to join. This has implications on the systems used as data has to be merged, giving rise to compatibility issues.

Software as a Service (SaaS)

A software licensing and delivery method in which software is licensed on a subscription basis and is centrally, remotely hosted.

Remote host

A computer that resides in some distant location from which data are retrieved e.g. a server in a private network or the public Internet or a user's PC in another location that is accessed for file transfer or remote control operation.

Methods of implementation

The ways in which systems are implemented in an organisation.

Parallel running

A new system is started while the old is kept running in simultaneously (side by side) for a while. All of the data is inputted to both systems, and the old system is stopped when the new system has been proven to work.

Pilot running

The new system is trialed in one part of the organisation (e.g. department) and once it is running successfully in that part it is implemented in the entire organisation.

Direct changeover

The old system is shut down and the new system is automatically turned on.

Phased conversion

The new system is split into a number of parts or modules, and replaces the old system by implementing modules in stages.

Data migration

The process by which data is transferred between storage types, formats or computer systems.

File formats

A standard way that information is encoded for storage in a computer file.

Data structure

A way of organizing data in a computer so that it can be used efficiently. Different kinds of data structures are suited to different kinds of applications.

Validation rules

Rules for checking that the data input is of the right type, range and format so that it is suitable for error-free processing.

Testing

Measures to check the performance, quality or reliability of a determined system. Needed to make sure if the system is working well and improve it if possible.

User acceptance testing

Process by which the actual software users test the software to make sure it can handle required tasks in real-world scenarios, according to specifications.

Debugging

The process of identifying and removing errors from computer hardware or software.

Beta Testing

Testing a software in final stages (prior to release) by releasing it to the end-users (unrelated with the development) to test complete functionality.

User documentation

Documentation for a product/service provided to the end-users, designed to assist them to use the product.

User training

Process of teaching a user how to use a new system. It is can be done by videos, lessons or by written instructions.

Data loss

When information is destroyed due to failures or neglect in storage, transmission or processing.

Releases

The process by which a computer system goes available to the market.

Updates

A new version of a system, which usually include new features and less bugs.

Patches

Fixes to program bugs, usually downloadable and inserted into an executable program.

Hardware

The physical components of a computer.

Software

Computer instructions or data stored electronically in a computer system that work as a program.

Network

Any set of interconnected computer systems that share resources and data.

Human resources

Humans employed in the use or building of computer systems.

Client

Desktop computer or terminal used to access a computer-based system.

Server

1. A program that provides services requested by client programs.
2. A computer that provides services to another computer connected over a network.

Email server

Computer within a network that runs software dedicated to sending, delivery and storage of electronic mail messages. Allows for quick communication which can be of critical importance.

DNS server

A computer in a network registered to join the Domain Name System. It translates host domain names into numerical IP addresses and contains a database of network names and addresses for other Internet hosts.

Router

A device that identifies the destination of messages and sends them via an appropriate route.

Firewall

Hardware or software that blocks unauthorised connections being made to a computer. Normal data is allowed to go through, but unknown data is blocked.

Stakeholders

People that get affected by the application and running of a system.

System requirements

The hardware and software components of a computer system that are required to install and use software efficiently.

Surveys

Structured questions with discrete possible answers, to gather information on the current system and the requirements of a new one.

Interviews

A structured conversation through which the interviewer can ask users or ex-developers questions about the system they require.

Direct observation

Research based on the observation of users using the current system.

Current systems

Research on system to be replaced which could raise ideas on how to improve it, and what are the valuable assets of it.

Competing products

Research on products similar to the one being developed, gives an idea of how it should look like and how it is being used.

Organizational capabilities

Research on the structure and different capabilities of the organization.

Literature searches

A research on academic work related to the system being developed. It clarifies ideas and findings.

Prototypes

A simple version of a system in the design stage, showing the user interface but without full processing behind it. This allows the user to propose changes at the design stage.

Iteration in design process

Throwaway prototyping: Prototypes are discarded in favour of a fresh implementation of the final design.

Usability

The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use.

Ergonomics

Computers intended to provide optimum comfort and to avoid stress or injury.

Accessibility

The extent to which people can use a product due to their physical or mental ability.

Usability problems

Problems which do not allow the user to fully use their device/system.

Central Processing Unit (CPU)

The brains of the computer where most processes take place as a series of calculations and logical comparisons.

Arithmetic Logic Unit (ALU)

A part of the processor that performs arithmetic calculations and logical decisions.

Control Unit (CU)

Processor component that manages the execution of instructions during the fetch-execute cycle.

Memory Address Register (MAR)

Holds the address in memory of the instruction at present being executed.

Memory Data Register (MDR)

Used to temporarily store data read from or written to memory. All transfers from memory to the CPU go via this.

Primary Memory

The part of the memory where the data and programs that are in use at the time are stored.

Random Access Memory (RAM)

A volatile memory which reads and writes very fast and temporarily stores running applications and files.

Read-only Memory (ROM)

A non volatile memory which stores a set of instructions which cannot be changed including the BIOS (Basic Input Output System) and the programs needed to boot up the computer.

Machine instruction cycle

A set of instructions that is constantly repeated which controls the processes of the CPU.

Data bus

The pathway that carries data to the ALU and from the ALU to memory.

Address Bus

The pathway between the memory and processing unit that carries the addresses in memory of data to be processed.

Non-volatile memory

Types of memory that retain their contents when power is turned off.

Volatile memory

Memory that loses its contents when no power is supplied.

Application software

A program or group of programs designed to help humans solve real-life problems e.g. word processor.

Computer Aided Design (CAD)

Computer systems used in the design of a product.

Graphic processing software

A program or a collection of programs that allow the user to manipulate visual images on a computer.

Toolbars

A series of selectable buttons in a GUI that give the user an easy way to select desktop, application or Web browser functions.

Menus

A display of a list of optional facilities that can be chosen by the user in order to carry out different functions in a system.

Dialogue boxes

Boxes used in GUIs to display an informative/warning/action message.

Graphical User Interface (GUI)

A program interface that takes advantage of the computer's graphics capabilities to make the program easier to use. Usually includes WIMP (Windows, Icons, Menus and Pointers).

Bit

Binary digit. The smallest unit of information for data storage and transmission. Each bit is considered to be either a "0" or a "1".

Byte

A set of bits consisting of 8 bits and corresponds to a single character of information.

Binary

A number system with base 2, that has two digits: 0 and 1.

Denary/Decimal

A system number with base 10, the most common way of representing numbers, digits range from 0 to 9.

Hexadecimal

A system of numbers with the base 16; hexadecimal digits range from 0 to 9 and from A to F, where A represents 10 and F represents 15.

String

A set of characters manipulated as a group.

Integers

A whole number.

Characters

A symbol that requires a byte of storage.

AND

It’s output is True if all statements are True, False if any statement is False.

OR

It’s output is True if at least one input is True, otherwise the output is False.

NOT

It’s output for a statement P is True if P is False, False if P is True.

NAND

It’s output is False only if all inputs are True, otherwise the output is True.

NOR

It’s output is True if all statements are False, False if at least one statement is True.

XOR

(Exclusive) It’s output is True if the two inputs are different; the output is False if the two inputs are alike.

Local Area Network (LAN)

A computer network in a small geographical area where all the computers are directly linked by cables and/or microwave transmission.

Virtual Local Area Network (VLAN)

Logical, not physical group of computers defined by software. Allows groups of computers to be on the same LAN while being in different physical locations.

Wide Area Network (WAN)

A network that provides communication services throughout a large geographic area, and that requires the use of a communications system.

Storage Area Network (SAN)

Type of local area network designed to handle large data transfers. Supports data storage, retrieval and replication.

Internet

Connected group of computer networks allowing for electronic communication.

Extranet

Network that allows controlled access from the outside. An external extension to a company's local network with limited access using internet protocols;

Personal Area Network (PAN)

A network with very short range of connections, aiming to get rid of cables for connecting peripherals.

Peer-to-peer (P2P)

Network of client computers connected together. No server, just clients. Does not use the internet.

OSI (Open Systems Interconnection)

A set of protocols allowing different types of computers to be linked together.

Virtual Private Network (VPN)

Private network that uses a public network to connect remote sites or users together. VPN authenticates the sender before establishing the tunnel, access & transmission is always encrypted.

Protocol

An internationally agreed set of rules to ensure transfer of data between devices. A standard protocol is one that is recognized as the standard for a specific type of transfer. For example, TCP/IP.

Data Packet

A unit of data sent across a network. Apart from containing a portion of the message it will have other data such as check digits, sender and receiver IP addresses and so on.

Data Integrity

The correctness of data after processing, storage or transmission.

Flow Control

Process of managing the rate of data transmission between two nodes. Prevents a fast sender from overwhelming a slow receiver.