Program Logic and Design Lecture

Pseudocode

Definition

• Pseudocode is an English-like representation of the logical steps it takes to solve a problem.
• Similar to writing steps for making a cup of tea:
  • Plug in the kettle
  • Put the tea bag in the cup
  • Add water to the kettle
  • Wait for the kettle to boil
  • Add water to the cup
  • Remove the tea bag
  • Add milk or sugar based on preferences
  • Serve

Characteristics

• Programs begin with start and end with stop (can also use begin and end).
• Each program statement performs one action (Input, Processing, Output).
• Program statements are indented a few spaces more than the start or module name.
• Each program statement appears on a single line if possible; continuation lines are indented.
• Program statements begin with lowercase letters to avoid auto-capitalization issues.
• No punctuation is used to end statements.
• Example of pseudocode for doubling a number: start input my number set my answer = my number * 2 output my answer stop

Flowcharts

Definition

• Flowchart is a pictorial representation of the logical steps it takes to solve a problem.
• Example: Fixing a lamp
  • Lamp doesn't work -> Is it plugged in? -> Yes/No -> Next steps (Plug in, Check bulb, etc.)

Characteristics

• Use various shapes to represent different types of statements:
  • Input/Output: Parallelogram
  • Processing: Rectangle
  • Start/Stop: Lozenge (race track shape)
• Flow lines (arrows) are used to show the direction of the process.

Compare Pseudocode and Flowcharts

• Think of them as maps (written directions vs. drawn maps).
• Client preferences generally favor flowcharts for their pictorial nature.
• Learning tool preference between pseudocode and flowcharts varies; studies show a majority of students prefer flowcharts.

Repetition (Loops)

Issue with Repetition

• Initial pseudocode/flowchart for doubling a number is only feasible for one number, not for large repetitions (e.g., 10,000 times).
• Infinite loops should be avoided as they never end.

Solution: Loops

• Create a loop to repeat a series of steps instead of writing redundant lines of code.
  • Example: Flowchart indicates repetition by having a flow line that loops back to previous steps.
• Upcoming topic: Using sentinel values to end loops.