Low Level Pseudocode

Objectives

• learn what low level pseudocode is
• learn how to use it to turn high level pseudo code into a non-syntax specific set of code

Context

Our process for writing code begins with a user problem statement. After we understand each step we need to implement the solution to the problem we can begin thinking about the code level implementation of each step.

Low-level pseudocode will help us map out what each logical step will require.

Approaching a Coding Problem (15 minutes / 0:35)

Pseudocode isn't just about writing down the steps that you already know. It's a tool to help you work through the problem. Before we can write pseudocode to solve the problem, we need to know the problem.

The process of writing a program is first understanding the problem well, then expressing it in our code in an explicit and elegant way.

We write programs using these cognitive tools: decomposition, abstraction, encapsulation and modeling. Pseudocode helps us work with these techniques.

Decomposition: In what ways can we break the problem down into it's constituent parts?

• Which parts of the sandwich making process are distinct and discreet?

Modeling: How do we represent our data?

• do we use an array or an object? A string or a number?

Encapsulation: How do we package the concepts of the problem together in a way that makes sense?

• Does the peanut butter belong with the jelly? Or does it belong with bread slice 1?

Abstraction: What do we use to generalize parts of our problem? How general do we make our program?

• Can we generalize our system for all kinds of jelly? What about jam, or even mustard?

Review: Steps to get to low level pseudocode: or, how to program.

1.Identify the Problem

• What exactly are we trying to solve?
• What are we delivering?

2.Conceptualize

• Look at the big picture
• Avoid details
• Whiteboards and pen-and-paper can be useful tools here

3.Break It Down - high level pseudocode

• Break the conceptual models down into concrete steps / actionable items
• Identify risks (e.g., gaps in knowledge and technology)

4.Break It Down Again - low level pseudocode

• write out a logical step for each item you came up with

Start Small, Stay Small

Write code using those small steps

• Verify that each step achieves what we want before continuing on
• If we do too much at once and things break, which they always do, we won't know what is causing the problem
• Humans thrive on easy wins and forward progress. Use this to your advantage.

Where Does Pseudocode Fit In?

"Break It Down"

This process is iterative. We keep circling around and repeating the earlier steps, just at a different level.

When we first approach a problem, we see the big picture. "Break it down" first into big steps. Then we take one of those steps and "Break it down" again into smaller steps. We write pseudocode to help illustrate the problem.

Pseudocoding proves that we have identified the problem, understand it conceptually, and have broken it down into small steps that we can follow.

Example 1

We want to know if a number is even or odd:

High-level pseudo code:

1. write a function to do it
2. we can check if the number is divisible by 2
3. if its not then its odd

Low-level:

PROGRAM IsEvenOrOdd:
  IF (number divided by two has no remainder) // modulo
      THEN Print the number is even;
      ELSE Print the number is odd;

You Do: Pseudocode Concentration (15 minutes / 0:50)

Take 10 minutes to pseudocode the game Concentration with a partner.

The user should see a grid of cards. Clicking a card reveals it and allows them to click another card. If they match, the cards stay up and if not they flip back over. Users get a point for every pair they flip. The game ends after 1 minute or all cards have been matched.

Afterwards, we'll spend 5 minutes sharing approaches as a class.

Conclusion

1. What are some helpful steps for solving problems?
2. What does pseudocode help us do?
3. Do we only pseudocode at the start of a project?

Resources

• Introduction to Pseudocode

Screencasts

• Pseudocoding