OCR GCSE Computer Science - Paper 2

Breaking a problem down into smaller sub-problems. Once each sub-problem is small and simple enough it can be tackled individually.

Decomposition is...

Removing or hiding unnecessary details from a problem so that the important details can be focused on or more easily understood.

Abstraction is...

Looking for similarities among and within problems.

Pattern recognition is...

Deciding on the order that instructions are carried out and identifying decisions that need to be made by the computer.

Algorithmic thinking is...

A graphical method of decomposing a problem, with each layer breaking down the layer above it into smaller and smaller sub-problems.

A structure diagram is...

A graphical representation of an algorithm and uses symbols to denote each step, with arrows showing how to move between each step.

A flowchart is...

A textual representation of an algorithm. It is very closely related to high-level languages, although it does not require the same precise syntax. It also enables programmers to communicate algorithms to other programmers without worrying about which language they know.

Pseudocode is...

A tool that can be used to follow each line of an algorithm through, step by step. A trace table will show the contents of each variable after each line has been carried out and will also show any output.

A trace table is...

Compares each item one by one until the target is found. There is no need for the list to be in order.

A linear search...

Compares the middle item to the target then discards half of the list which the target can't be in. It then finds the next middle item, and repeats until the target is found.

A binary search...

Goes through each pair, swapping if needed, in one pass. I then repeats the passes until a pass happens with no swaps.

A bubble sort...

Divides the list continuously by two until each list has 1 item. It then combines two lists at a time, which keeps the items in order.

A merge sort...

Starts with 1 item in the 'sorted part' and moves items one by one from the 'unsorted part' to the 'sorted part'.

An insertion sort...

Used to temporarily store information to be referenced and used by programs.

A variable is...

Typically just contains items of the same data type and is of a fixed length. Assume that indexing starts at 0 unless told otherwise.

An array...

The testing of modules throughout development. Any issues found will be fixed and then the module should be retested.

Iterative testing is...

The testing of the whole program at the end of the development.

Terminal testing is...

Code doesn't follow the rules of the programming language.

A syntax error occurs when...

Code does not do as you intend.

A logic error occurs when...

Enforcing a rule around user input.

A validation check is...

Checking the identity of a user e.g using password checkers.

Authentication is...

Negation - Inverts the input and outputs it e.g TRUE = FALSE.

NOT gate:

Conjunction - Both inputs need to be true for a true output e.g TRUE & TRUE = TRUE, TRUE & FALSE = FALSE.

AND gate:

Disjunction - One input out of two needs to be true for a true output e.g TRUE & TRUE = TRUE, TRUE & FALSE = TRUE.

OR gate:

Are like written English, more readable, portable (can run on many CPUs), but are slower to execute.

High-level languages...

The two types of low-level languages are assembly and machine code. They are also easier to optimise but are specific to particular CPUs.

Low-level languages are...

Convert one programming language to another. Only machine code doesn't need to be translated to run.

Translators are programs which...

Produce an executable file and no source code is needed after this. They are fast to execute but errors are only shown right at the end.

Compilers...

Translate an instruction, then execute it. Errors are discovered straight away as code is ran line-by-line, checking for errors on each line but the source code is needed to run and it is slower to execute.

Interpreters...

Providing an editor, providing error diagnostic tools, having a run-time environment and using a translator so it is able to run.

IDEs support programming by...