Algorithms & Pseudocode

Algorithms An algorithm is a detailed set of steps to solve a problem It states the actions to be executed and the order in which they are to be completed Algorithms can be described using pseudocode or a flowchart Algorithms are fundamental to computer programming

Developing an algorithm High Level Algorithm Written in pseudocode or drawn as a flowchart, it describes how the problem will be solved without the fine detail Detailed Pseudocode Expands the logic of the high level algorithm to closely match a real program Real Code Line by line conversion of the pseudocode to real code.

Important Constructs There are 3 important constructs used in algorithms and coding that you need to be familiar with: Sequence The order that instructions are executed. Order is important eg: Clean teeth Get out of bed Selection Making a decision based on certain conditions eg: If its raining then I’ll stay indoors Else I’ll go to the park Iteration Another name for repeating a set of actions While I feel hungry Eat more food

Pseudocode Pseudocode is an artificial language that helps programmers develop algorithms. It is intended to be easy to read and free from the strict formal syntax of a programming language The rules of pseudocode are reasonably straightforward – there should be a line of pseudocode for every line of real code in your program

Example 1 - Student grades Task: A program is required to output ”passed” if a student achieves 60 or more marks otherwise failed High Level Algorithm Pseudocode If student's mark is greater than or equal to 60 Display"passed" else Display "failed" If mark >= 60 Print "passed" else Print "failed" In this example the problem to be solved, high level algorithm and pseudocode are similar because of the very fact that it is a simple program. However, that should not prevent you from completing the process!

Example 2 – Class Average Task: A program is required to input the individual marks and calculate the average score for a class of 10 students High Level Algorithm Pseudocode Initialise variables Loop add 1 to count input mark calculate average Until count > 10 Display average average  0, class-total  0, mark  “” For count  1 to 10 mark  userinput (”enter student’s marks”) class-total  class-total + mark average  class-total/count Next count Useroutput (“class average is “, average) Now the value of the high level algorithm becomes clearer. It shows the “big picture” of how the problem is to be solved Finer detail is added in the pseudocode ie: Variables to be used type of loop (for or while) Calculation of average