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Writing pseudocode

From: Foundations of Programming: Fundamentals

Video: Writing pseudocode

It's really easy for people to get stuck. They want to write a program and they start off looking at a blank text file and they're thinking so much about syntax and case sensitivity and curly braces and all the thousand other things to remember, that it is very easy to now, actually know, how do I start typing? Well, step one is don't. Step one is instead get away from the computer, grab a piece of paper or find a whiteboard and start writing what's called pseudocode instead. Now pseudocode is not a language.

Writing pseudocode

It's really easy for people to get stuck. They want to write a program and they start off looking at a blank text file and they're thinking so much about syntax and case sensitivity and curly braces and all the thousand other things to remember, that it is very easy to now, actually know, how do I start typing? Well, step one is don't. Step one is instead get away from the computer, grab a piece of paper or find a whiteboard and start writing what's called pseudocode instead. Now pseudocode is not a language.

It's the term for writing your computer instructions in plain English to the point where it's readable by anyone who understands the problem, whether they come program or not. Let me show you a few examples. On a whiteboard or paper I might just write something like this. Ask user for email address. If email address matches accepted pattern, add them to email list, else show error message. Something like this. Pseudocode doesn't have formal rules, but this would be quite common to see.

Now where I'd said, ask user for email address, I could've said get email address or prompt for email address or if I really wanted to break it out I could even say create email variable, ask user for email address, store user's email address in email variable. Now that would be a little long. Or I could just say get email. I'm just trying to define the structure of this code, what has to happen in my problem. Now it's quite common to see programming keywords like if and else and while and for, but it's whatever makes sense. And you'll also see pseudocode often indented like I've done here, and like any indentation it just makes it easier to follow the structure.

And different people write pseudocode in different ways. The longer someone's been writing a language, the more their pseudocode tends to take on the style of that language. Sometimes you'll see pseudocode written partly in uppercase like this, and it's quite common to see people explicitly marking where an if or a loop ends using a phrase like END IF or END LOOP, and it's just serving the same purpose as a closing curly brace in JavaScript or another C-based language. But there are no rules. The point is clarity and understanding.

Can you read the pseudocode? Does it make sense? Here's an example perhaps of going through a whole list of numbers and adding them together. We start off with set total to zero, get a list of numbers, loop through each number in the list, and add each number to total, remark where the loop ends. If number more than zero, print its positive message, else print its zero or last message, end if. It's the kind of thing that should make sense whether you can program or not. Now if you start worrying about pseudocode syntax, it's kind of missing the point.

The whole point of this is to get away from that, where you don't have to worry about braces, parentheses, brackets, off by one errors, naming conventions. It's whatever seems natural. Now it doesn't necessarily break down perfectly to one line of pseudocode, one line of real code. Sometimes one line of pseudocode like send email can cause several lines of real code. One of the best things about pseudocode is it lets you think about your problem without necessarily knowing exactly how to code it and it exposes where you need to go and learn something. Because I can describe a problem in pseudocode without having the necessary knowledge in that language.

Let's say I'm trying to build a game and I know how to work with images. I've been programming some of it already. So I might write some pseudocode code like this. If a missile-image touches the spaceship -image, well, I'm going to replace this spaceship-image with the explosion-image. I want to play an explosion sound and then I better check, is the remaining-lives counter zero? Because if it is, they don't have any lives left, so I'll show the "game over" message. But if it's not zero, I'll subtract one from their remaining lives.

I'll show begin message, I'll reset the spaceship to the starting position, etcetera, etcetera. Now I'm not saying this is necessarily the perfect pseudocode for a game, but we're following the steps here. But let's say I don't know how to play a sound in the language that I'm working with. It doesn't matter. I can still build my pseudocode. I can still write this problem out, because I know that sound has to happen. I can just put it on my personal task list for something to look up and find out how. I just write down "research how to play short sound effect." Go and figure that out and later I can come back and code this.

So pseudocode is not just for beginners. Many very experienced software developers I know still work out a lot of their problems in pseudocode as a way of better understanding it without worrying about syntax, and it's a great habit to get into to start sketching out your programming ideas in plain English before you write code.

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This video is part of

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Foundations of Programming: Fundamentals

61 video lessons · 88646 viewers

Simon Allardice
Author

 
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  1. 4m 15s
    1. Welcome
      1m 17s
    2. Making the most of this course
      2m 8s
    3. Using the exercise files
      50s
  2. 22m 11s
    1. What is programming?
      5m 45s
    2. What is a programming language?
      4m 48s
    3. Writing source code
      5m 34s
    4. Compiled and interpreted languages
      6m 4s
  3. 16m 29s
    1. Why JavaScript?
      4m 45s
    2. Creating your first program in JavaScript
      6m 54s
    3. Requesting input
      4m 50s
  4. 31m 38s
    1. Introduction to variables and data types
      5m 16s
    2. Understanding strong, weak, and duck-typed languages
      3m 51s
    3. Working with numbers
      5m 4s
    4. Using characters and strings
      4m 5s
    5. Working with operators
      4m 47s
    6. Properly using white space
      6m 46s
    7. Adding comments to code for human understanding
      1m 49s
  5. 24m 48s
    1. Building with the if statement
      7m 35s
    2. Working with complex conditions
      4m 9s
    3. Setting comparison operators
      6m 59s
    4. Using the switch statement
      6m 5s
  6. 17m 54s
    1. Breaking your code apart
      4m 1s
    2. Creating and calling functions
      2m 56s
    3. Setting parameters and arguments
      6m 7s
    4. Understanding variable scope
      2m 23s
    5. Splitting code into different files
      2m 27s
  7. 13m 31s
    1. Introduction to iteration
      4m 28s
    2. Writing a while statement
      5m 24s
    3. Creating a for loop
      3m 39s
  8. 19m 28s
    1. Cleaning up with string concatenation
      4m 30s
    2. Finding patterns in strings
      8m 3s
    3. Introduction to regular expressions
      6m 55s
  9. 19m 58s
    1. Working with arrays
      5m 46s
    2. Array behavior
      5m 29s
    3. Iterating through collections
      5m 18s
    4. Collections in other languages
      3m 25s
  10. 10m 50s
    1. Programming style
      5m 55s
    2. Writing pseudocode
      4m 55s
  11. 25m 55s
    1. Input/output and persistence
      3m 6s
    2. Reading and writing from the DOM
      8m 11s
    3. Event driven programming
      7m 47s
    4. Introduction to file I/O
      6m 51s
  12. 24m 25s
    1. Introduction to debugging
      5m 57s
    2. Tracing through a section of code
      7m 5s
    3. Understanding error messages
      3m 21s
    4. Using debuggers
      8m 2s
  13. 14m 16s
    1. Introduction to object-oriented languages
      5m 18s
    2. Using classes and objects
      6m 28s
    3. Reviewing object-oriented languages
      2m 30s
  14. 11m 14s
    1. Memory management across languages
      5m 11s
    2. Introduction to algorithms
      4m 2s
    3. Introduction to multithreading
      2m 1s
  15. 29m 20s
    1. Introduction to languages
      1m 42s
    2. C-based languages
      4m 40s
    3. The Java world
      3m 13s
    4. .NET languages: C# and Visual Basic .NET
      6m 17s
    5. Ruby
      3m 4s
    6. Python
      2m 56s
    7. Objective-C
      4m 3s
    8. Libraries and frameworks
      3m 25s
  16. 1m 2s
    1. Where to go from here
      1m 2s

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