OCR A-Level Computer Science Software and software development overview quiz quiz

Real-time operating system

Multitasking operating system

Distributed operating system

Multiuser operating system

spread across many networked computers so that processing is shared between several physical machines

built into a dedicated device with limited resources and a fixed function

designed to support many users signed in at the same time from separate terminals and accounts

able to run many large applications at once on a general-purpose desktop or laptop computer

Waterfall

The compilation model

Agile

Sequential design

It adapts easily to late requirement changes because each phase can be revisited at any time

It shows the customer working software from the first week through frequent small releases

It needs no analysis phase, since requirements are gathered gradually as the project proceeds

It produces clear documentation and well-defined milestones

produces a fast standalone executable that can be distributed without the source

reports only the first error it meets and then stops translating the rest of the program

needs the source code to be present and re-translated every single time the program is run

translates and executes the program one statement at a time as the program is running

Syntax analysis, where the token stream is checked against the grammar

Lexical analysis

Code generation, where object code is produced from the parsed program

Optimisation, where the generated code is improved for speed or size

To load the finished executable into main memory so that the processor can begin running it

To break the source code into individual tokens during the first stage of the compiler

To combine compiled modules and library code into a single executable

To check the program against the language grammar and report any syntax errors that it finds

a template that defines the attributes and methods shared by every member of a group

a private attribute that can only be reached through the public methods of its class

a special method that initialises a class and sets up the starting values of its attributes

a specific instance of a class with its own attribute values

keeping attributes private and accessing them only through methods

a subclass inheriting the attributes and methods of a superclass that sits above it

the same method call behaving differently depending on the actual object that receives it

translating high-level source code into the machine code that the processor can execute

two developers sharing one keyboard so they can write and review the same code together at once

a Circle and a Square each overriding an inherited draw() method to draw themselves differently

storing the program's source code openly so that anyone is free to inspect and modify it

a fixed sequence of development phases worked through strictly in order from start to finish

Its source code is kept secret from users so that nobody outside the company can read it

It can never be used by a business, as its licence forbids any commercial use whatsoever

Its source code is freely available to inspect and modify

It always comes with a guaranteed paid support contract from the original development team

It is always cheaper than an equivalent off-the-shelf package bought from a software vendor

It needs no testing, because software written to order is guaranteed to be free of defects

It is available immediately, since bespoke software can be downloaded and installed at once

It fits the organisation's exact requirements and can integrate with existing systems