2.1 - Algorithms

• 3 Types of Computational Thinking

  • A - Abstraction
  • D - Decomposition
  • AT - Algorithmic Thinking
• Abstraction:

  • Identifying key parts of the problem and hiding those that are less important
  • Leaving out unnecessary details and only including important details
• Decomposition:

  • Breaking down one large complex problem into smaller sub-problems so it is easier to solve
  • Done by using a structure diagram
  • Steps: Identify main problem, List main components/functions, Break them down into smaller components
• Algorithmic Thinking:

  • Consideration of steps that go into solving a problem
  • Algorithm - Series of steps that a program needs to perform or solve a problem
• The input is what is entered by someone on a keyboard
• A process is how the data inputted is handled throughout the program (arithmetic, sorting a list)
• An output is the end result after processing
• Arrow represents the flow of control passing between stages

  
• A parallelogram is used to represent an input or output

  
• A rectangle is used to show a process or calculation

  
• A diamond/rhombus is used to represent a decision

  
• An oval/terminal symbol is used to represent the start/end of a program

  
• This is used to represent a subroutine

  
• Pros and cons of Pseudocode:

  • (+) Can be easy to understand for many people
  • (+) Doesn't matter if there are syntax errors
  • (+) Changes can easily be incorporated
  • (-) Is hard to see how a program flows
  • (-) It can be time consuming to produce
• Pros and Cons of flowcharts:

  • (+) Easy to see how a program flows
  • (+) They follow an international standard - any flow diagram user can understand it
  • (-) Large programs can cause them to be hard to follow
  • (-) Any changes means a lot of the diagram has to be redrawn
• A trace table is used to show how the values of variables change throughout the program

  EXAMPLE:

  
• Common types of errors:

  • Syntax error: Occurs when a statement doesn't meet the rules of the language
  • Logic Error: Occurs when the output is not what the user intended it to be