Algorithms and Programming Techniques Glossary (Appendix B)

Algorithm

A clear, unambiguous step-by-step set of instructions that solve a problem. Independent of any programming language.

IPO chart

A table that lists the Inputs, Process and Outputs of a problem. The first step in designing an algorithm.

Variable

A named storage location whose value can change as the program runs. e.g. orderTotal

Constant

A named storage location whose value cannot change as the program runs. e.g. pi = 3.14159

Data type

The kind of data a variable holds: integer, real, character, string, Boolean, etc.

Pseudocode

A way of writing the logic of a program in structured plain English. Independent of any programming language.

Sequence

Instructions that run one after another, top to bottom

Selection

Choosing which instructions to run based on a condition. Uses IF/ELSEIF/ELSE/ENDIF.

Iteration

Repeating a set of instructions. WHILE/ENDWHILE tests the condition first; REPEAT/UNTIL tests it after.

Condition

A logical expression that evaluates to TRUE or FALSE e.g. age > 18

Module/function

A chunk of code that does one thing and can be called from elsewhere

Modularisation

Breaking a large problem into smaller, independent modules.

Abstraction

Hiding details inside a module. The caller doesn’t need to know how it works.

Local variable

A variable that exists only inside one module.

Global variable

A variable that is available to every module in the program.

Complier

What translates the whole program from a high-level language to machine instructions before running.

Interpreter

What translates the program line-by-line at runtime (e.g. JavaScript in your browser).

Syntax

The strict set of rules of a programming language.

Logic error

When a program runs but produces the wrong output. Can be caught by desk checking.

Syntax error

When a program won’t run because of a rule violation in the language.

Trace table

A table used during desk checking to record every variable’s value at every step.

Flowchart

A diagram of an algorithm using oval, parallelogram, rectangle, diamond and hybrid symbols.