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Reading Code

Reading Code

As developers, we spend a lot of time learning to write code, while spending little to no time learning to read code. Meanwhile, we often spend more time reading code than actually writing it. Shouldn’t we be spending at least the same amount of time and effort improving this skill? Deliberate practice can help us get better at reading code. Learning how to better read and understand code, can in turn teach us what makes code readable. This might even help us to write code that is easier to read.

In this talk we will discuss the benefits of deliberately practicing reading code in a code reading club or session without an IDE, as well as common strategies to navigate a new codebase and familiarise ourselves with the code using the IDE.

Marit van Dijk

October 19, 2023

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  1. Reading Code Introduction We read code when: • adding features

    • fi xing bugs • understanding a new system • doing code reviews • learning new technologies • etc.
  2. Reading Code Introduction "developers on average spend as much as

    58% of their time comprehending existing source code" - Felienne Hermans, The Programmer's Brain
  3. Reading Code Introduction • We spend more time reading code

    than writing code • But we don't practice reading code explicitly (much)
  4. Reading Code Introduction "How to teach programming (and other things)?"

    by Felienne Hermans https://www.youtube.com/watch?v=g1ib43q3uXQ
  5. Reading Code Introduction Code can be confusing because of •

    Lack of knowledge • Lack of information • Lack of processing power in the brain
  6. Reading Code Introduction Lack of information • Unknown details •

    Unfamiliar names • Code connected in unknown ways • Too many things at once
  7. Reading Code Introduction Dealing with lack of processing power in

    the brain • Memory aids • Dependency graph • State table
  8. Reading Code Introduction State table public class NestedLoop { public

    static void main(String[] args) { for (int i = 0; i < 2; i++) { System.out.println("i is: " + i); for (int j = 0; j < 2; j++) { System.out.println("j is: " + j); } } } } i j 0 0 0 1 1 0 1 1
  9. Reading Code Understanding a piece of code Examples of exercises

    • First glance • Identify components & relationships • Most important lines • Identify concepts • Summary
  10. Code reading exercise Code Structure: Roles of variables • (20

    min) Together - Discuss the roles of variables
  11. Reading Code Understanding a piece of code Structured exercises •

    Code Reading Club Resources: • https://github.com/CodeReadingClubs/Resources • The Programmer's Brain - Felienne Hermans • Code Reading in Practice - Felienne Hermans & Gien Verschatse
  12. Reading Code A slice of the application • Find a

    starting point • Generic • Main method • Endpoint • Speci fi c • Error message / Exception • Logic / Functionality
  13. Reading Code Introduction A good place to start: • Check

    out the code • See if you can build it
  14. Reading Code The bigger picture Strategies: • Identify components •

    Identify relationships / dependencies • Identify concepts
  15. Code reading exercise First glance The goal of this exercise

    is to practice getting a fi rst impression of code. (1 min) Independently - Glance at the code Note down the fi rst thing that catches your eye. Then note the second thing that catches your eye. Think about why you noticed those things fi rst.
  16. Code reading exercise Dependency graph The goal of this exercise

    is to get a feel for the structure of the code. (5 min) Independently - Examine structure Variables 1. Go through the code and underline all variables 2. Then draw a link between variables and their uses Function / method calls 3. Go through the code and circle all methods / function calls 4. Then draw a link between methods and their invocations Instantiation 5. Go through the code and draw a box around all instances of classes 6. Then draw a link between classes and their instances
  17. Code reading exercise Most important lines The goal of this

    exercise is to start to think about which lines in the code de fi ne its essence, have the biggest impact or need to be paid close attention to. (5 mins) Independently - Identify most important lines Brie fl y discuss what it means to be important as a group (if you want to). Then, identify the 5 lines you consider most important.
  18. Code reading exercise Concepts (5 min) Individually - Central thematic

    concepts Name the 5 most central concepts of the code. These could be names, themes, classes, or information found in comments.
  19. Code reading exercise Summary The goal of this exercise is

    to think about the core purpose or function of this code. (5 mins) Independently - Summarize Try to write down the essence of the code in a few sentences.