You can call them N-S Diagrams if you’d like

There are many different ways of describing an algorithm in the Design phase:NS DiagramsFlowchartsPseudo code…

NS Diagrams are useful for encouraging some aspects of structured programming techniques.

NS Diagrams are noticeable by their ‘building blocks’ form, of which there are 4 main types..

Any algorithm should be able to be constructed using one or more of the 4 main parts of an algorithm:Process – a single stepConditional – dependant upon choiceIteration – loop until a condition is metModule - a grouping of the above which can be

referenced multiple times, from multiple places.

A process block is used to represent a single action

An algorithm is composed of steps or primitives.

E.g.:

Or multiple together:

Process (single step)

Get an egg

Get an egg

Crack the egg

Used to represent a condition leading to two possible actions (also known as a Boolean)

A branching action is represented by two blocks side by side meaning: perform the action on the left if the condition is true, or else perform the action on the right if the condition is false.

E.g.:

A multiple branching block is used when there are several alternative actions:

E.g.:

A test first loop block is used when a set of actions are to be repeated under a particular condition.

The condition is tested firstRepeated action is represented by

a block within a block, meaning repeat the action under the conditions stated

Because a test first loop is tested before any actions it is possible that no actions take place.

Conditional iteration:

A counted loop is also a test first loop – repeating the actions a set number of times and are counted before taking place.

NOTE: the counting starts before the loop begins. ‘1’ happens before any eggs are broken in.

A test last loop is used when a process is repeated under a particular condition.

The condition is tested last

These repeated actions are tested at the end of the loop.

E.g. making a pancake mix:The actions in a test last loop

are always carried out at least once because the test occurs after the actions have occurred. So a little milk will always be added and stirred.

A sub process block or module is used in instances where the process is large enough to warrant a separate design or where the process is used several times in the same diagram.

1. Completea. Why are N-S diagrams used when designing

algorithms?b. What are some other algorithm design tools?

2. What is being tested in test first and test last loops?

3. Express this part of an N-S diagram in words:

Follow the instructions :

Create an N-S diagram for one of the recipes in K:\Files\IPT\SSE\recipe