03. Introduction to Algorithms

Learning Outcomes

You will learn to:

Describe the decomposition of a problem

Describe what an algorithm is

Describe Psuedocode

Describe flowchart and flowchart shapes

Write a simple algorithm to calculate the area of a circle.

Resource

One of the best resources is the teach-ICT.com site.  Please use the following link:

http://www.teach-ict.com/gcse_computing/ocr/216_programming/algorithms/miniweb

Definition

An algorithm is simply a set of instructions for performing a task. Some algorithms are more efficient than others and we will look at these in more detail later in the course.  The purpose of an algorithm is to find a solution to a problem of to complete a goal in the most efficient and effective way possible.  A program is a set of instructions which have been written in a lNguage the computer understands in order to make the algorithm work.

Decomposition

The reason for introducing this topic now is that in order to program well you are going to need to think like a computer - particularly when you do your controlled assessment.  You need to decompose or break tasks down into small chunks so that they are easy to follow and impossible to get wrong.

Penalty Kick Algorithm

Look at the following algorithm for taking a penalty kick.  Try to work out what is wrong with it.  Remember the objective of a penalty kick is obviously to score a goal.

1. Start

2. Place football on penalty spot

3. Kick ball

4. End

TASK 1

In pairs write an algorithm for taking a penalty kick which will result in a goal being scored.

Lift Algorithm

Look at the following algorithm and work out why this one achieves all it's objectives efficiently and effectively:

1. Start

2. Wait until doors are closed

3. Wait until the floor button is pressed

  If button pressed is > than current floor

     Move lift upwards

  If button pressed is < than current floor

     Move lift downwards

4. When current floor = button pressed

5.  Open doors

6. End

TASK 2

Write an algorithm to calculate the area of a circle.

Flowcharts

Now let's explore the teach-ICT.com pages on Flowcharts

http://www.teach-ict.com/gcse_computing/ocr/216_programming/algorithms/miniweb/pg7.htm

Homework

Select either your algorithm for calculating the area of a circle or the lift operation algorithm in recreate as a flowchart.