OCR GCSE CS Paper 2

Abstraction

Simplifying a problem by ignoring unnecessary information

What is decomposition

Breaking a problem down into smaller tasks so that it is easier to solve

What is alogithmic thinking

Following logical steps to solve a problem

What does this do in a flowchart

Start/stop terminator

What does this do in a flowchart

Process

What does this do in a flowchart

Decision (if statement)

What does this do in a flowchart

Input/Output

What does this do in a flowchart

Subroutine

What is an algorithm

A set of instructions in a logical sequence used to solve a problem

How does binary search work

Selects the midpoint of the list, compares to the value, removes part of the list depending on whether the data was higher or lower

How does merge sort work

‘Divide and conquer’, divides a list in half over and over until everything is separate, then everything is merged together again in order

How does bubble sort work

Repeated passes through the data set, swapping items if they are not in the correct order.

Stops when a pass occurs with no changes made

How does insertion sort work

Starting from the first value, compare a value to everything before it and move it into the correct position

Advantages of local variables

Saves memory, easier to debug, subroutines using them can be reused

Advantages of global variables

Variables can be used anywhere, can be used for constants

What does // do

Integer division - shows the ‘whole number of times’ a number goes into another

15 // 6 = 2

What does % do

Modulo division - shows remainder

15 % 6 = 3

What is the word for datatype conversion

Casting

In a 2D array table, what is the order to read it?

Row then column

What is the basic SQL structure

SELECT FROM WHERE

What is an example of a wildcard in SQL

*

What are the things to consider to ensure a program is secure and robust

Anticipating misuse

Input sanitisation

Validation

Verification

Authentication

Maintainable code

What are the types of input validation

Range check

Type check

Format check

Presence check

Lookup table to limit inputs

Length check

What makes programs maintainable

Subroutines

Indentation

Naming conventions

Comments

Constants

Types of testing

Iterative testing

Final testing

Four types of test data

Normal data

Boundary data

Invalid data

Erroneous data

Why do programmers use high level languages

Easier readability as closer to human language

Faster development

Portability across different platforms

What are low level languages for

Speed or direct interaction with hardware e.g. drivers

Two types of low-level language

Machine code, Assembly language

What is machine code

0111001001010101010010101010010010100101001

What does a translator do

Changes a program to another language, usually machine code

Interpreter

Converts high level language one line at a time and executes it

Compiler

Converts high level language at once for execution at a later date

Interpreter vs compiler complexity

Interpreters are smaller, simpler programs

Interpreter vs compiler execution speed

Interpreters must translate every time, compilers create more efficient code making the programs run faster

Interpreter vs compiler error reporting

Compiler analyses the entire program and records location of errors in an error file

Interpreter stops the program from running when it reaches an error

Interpreter vs compiler repetition

Compilers must recompile whenever a change is made, however does not have to recompile whenever the program is run

Interpreters have to translate every time they are run even without changes

IDE features

Editor

Translators

Break point

Variable watch

Trace

Error diagnostics and debugger

Editor purpose

Editing cos

Low level language definition

A language close to the computer’s instruction set