Computer Science IBDP Theory (no programming)

IBDP Computer Science Revision Notes All Topics

Non-digital computer

a computer that uses mechanical or analog components to perform calculations, rather than digital signals.

Luddite

a person who opposes the use of technology, especially in the workplace.

Transistor

a semiconductor device used to amplify or switch electrical signals.

What are the three main parts of the transistors and what do they do?

Source - supplies the electric current

Drain - receives the electric current

Gate - controls the flow of electric current

What are the three main features of transistors?

No moving parts - less prone to breaking

Semiconductor materials - control the flow of electric current

No human input - switch on and off remotely

How do transistors work?

controlling the flow of electric current between two terminals

What is TELOS?

Technical Feasibility

Economic Feasibility

Legal Feasibility

Operational Feasibility

Schedule Feasibility

PDLC

Project Development Life Cycle

Stages of PDLC

Analysis

Design

Coding

Testing

Implementing

Alpha testing

A type of Acceptance Testing performed by the testers who are part of the organization. It is the final stage of testing.

It is used to identify any issues in the system.

Beta testing

An opportunity for real users to use a product in a production environment to uncover any bugs or issues before a general release.

Reasons for change management

Cost - too expensive to maintain or upgrade

Efficiency - system is inefficient and can be improved

Security - has security vulnerabilities

User Friendliness - difficult to use

Legacy system

an old method, technology, computer system, app or application program that may or may not be supported or available for purchase anymore

Business merger

when two or more businesses join together to form a single company

Reasons for business mergers

Cost savings

Increased efficiency

Improved Competitiveness

Software Incompatibility

when different software systems are not compatible with each other.

Data Migration

the process of transferring data from an old software system to a new one

Difficulties in changing software systems

User resistance

Data loss

Cost

Performance issues

Direct changeover

stop running the old system and start running the new system immediately

Parallel Running

run both the old and new system simultaneously, with new data being entered into both systems.

Pilot system

test the new system with a small part of the organization, refine it, and then expand it to the entire organization

Phased Implementation

introduce features of the new system in phases, while gradually phasing out the old system.

Dry-run testing

conducted using pen and paper by the programmer to test the system.

Verification checks

used to ensure that data has been input correctly.

Factors affecting the rate of implementation

Quality of user documentation

Time

Cost

Disadvantages of online documentation

System Dependency

Internet Reliance

Navigation Challenge

Self-instruction/Self study

learning independently using resources like documentation, videos, and books to master concepts, focusing on self-motivation, planning, and evaluating your own progress, rather than relying solely on a teacher

Formal Classes

structured, planned learning sessions within an educational institution led by qualified teachers, following a set curriculum, using standardized assessments

Remote/online training

where instruction happens outside a traditional classroom, using digital tools like video calls, online platforms, and multimedia to connect teachers and students

Product Release

the process of launching a new product for a specific market or user base.

Update

a software file that contains fixes for problems found by other users or the software developer.

Patch

a software update comprised code inserted (or patched) into the code of an executable program.

Common types of release management

Continuous delivery

Agile software development

Continuous delivery

produce software in short cycles, ensuring that the software can be reliably released at any time.

Agile software development

requirements and solutions evolve through the collaborative effort of self-organizing and cross functional teams and their customers/end users.

Data loss

refers to an error condition where data is lost or destroyed due to system failure, storage negligence, or even transmission or processing errors.

Four causes of data loss

Accidental Deletion

Building Fires

Data Corruption

Power Failure

Hardware

the physical parts of a computer and related devices.

Peripheral device

any external device that provides input and output for the computer.

Network

multiple devices that communicate with one another using a transmission medium.

Software

describes computer programs or sets of instructions

Human Resources

both the people who work for a company or organization and the department responsible for managing resources related to employees

Client

a computer that gets information from another computer called server.

Server

a computer that provides data to other computers.

Client-Server Model

how a server provides resources and services to one or more clients.

Router

a hardware device that routes data from a LAN to another network connection.

DNS Server

uses domain names to serve as memorisable names for websites and other services on the internet.

Firewall

acts as a barrier between a trusted system or network and outside connections, such as the internet. A computer firewall is more of a filter than a wall.

How to prevent system or hard drive crashes

Regular backup of files

Firewall installation

Data storage in two or more location

Removed hard copies

Online autosave backup

Redundancy

the duplication of storage devices and stored data of a computer system with the intention of securing the stored data.

Failover System

a computer system which is on standby capable of switching to a spare computer system upon hardware failure, network failure, or any other type of error, such as software malfunction.

Peer-to-peer network

a network model in which computers or hardware devices exchange files.

PAN

a network covering a very small area, usually a small room. e.g. Bluetooth

LAN

a group of connected computing devices within a localized area that usually share a centralized Internet connection. e.g. Wi-fi

WAN

a network connecting computers over large geographical areas like cities, countries, or globally.

VPN

creates a secure, encrypted "tunnel" over a public network like the internet, connecting your computer to a remote server, which masks your IP address and encrypts your data, making your online activity private and safe from snoopers, hackers, or ISPs, crucial for remote work and public Wi-Fi security. 

Extranet

a controlled private network allowing customers, partners, vendors, suppliers and other businesses to gain information, typically about a specific company or educational institution, and do so without granting access to the organization's entire network.

WLAN

a wireless distribution method for two or more devices that use high- frequency radio waves and often include an access point to the Internet.

SAN

a secure high-speed data transfer network that provides access to consolidated block-level storage.

VLAN

a logical group of workstations, servers and network devices that appear to be on the same LAN despite their geographical distribution.

OSI model layers

physical layer

data link layer

network layer

transport layer

session layer

presentation layer

application layer

Physical layer (OSI Model)

lowest layer of the model and is concerned with the transmission and collection of raw data over a physical medium.

Data link layer (OSI Model)

ensures error free transmission of data over the physical layer.

Network layer (OSI Model)

decides the route that the data takes through a series of network nodes.

Transport layer (OSI Model)

ensures that packets are delivered error free and in sequence.

Session layer (OSI Model)

establishes the establishes the session between the end points in the process.

Presentation layer (OSI Model)

considered as a translator between the application and the network and deals with such things as encryption and compression.

Application layer (OSI Model)

serves the window for the user and other application processes that access network services such as email remote file access