## The TL;DR Code is **step by step directions, but for computers**. - Code is a way to **tell your computer what to do** under different circumstances - All code eventually gets broken down into **ones and zeros** - Developers write code in lots of **different languages** built for different purposes - Most code that people write today is built on **packages of other people’s code** Code is probably the most fundamental building block of the difference between life today and life 20 years ago. ## Code is just telling a computer what to do The goal of any piece of software – as large as Gmail or small as a little calculator – is to **get something done**. The easiest way to understand code is to try and think through how you’d get that *thing* done, step by step. If we wanted to build Gmail, or any email client, we’d need to make sure it does a few things: - Show me my emails - Let me send and reply to emails - Let me mark emails as junk or flagged And if we wanted to dive deeper into one of these – let’s choose *Let me send and reply to emails* – we could break it down into even *more* specific tasks: - A text editor to write emails - Address fields to put in recipients and cc / bcc - A little “swoosh” sound when we send an email We can also break these into *even more* specific tasks – let’s choose *Address fields to put in recipients and cc / bcc*: - A cc field - A bcc field - Show cc in sent emails, but don’t show bcc - Auto-complete email addresses in these fields You get the point by now. Every [“feature”](/posts/how-does-a-feature-get-shipped) – or *thing* you want to build – eventually breaks down into “when your user does X, the program does Y.” Code is how you make that happen in practice. To make this even more concrete, let’s take a look at a little app I built last year called SNQL – it helps you track the sneakers you own and when you wear, trash, or sell them. I…need help. Here’s what it looks like *(I know, it’s not pretty)*: ![add sneakers form](/images/posts/whats-code/add-sneakers-form.png) When you add in a new pair, it gets stored in a database. So the *code* needed to build this program was pretty simple: HTML/CSS to build and style the web page, and Python to add the data you’re inputting into the form into a database on the backend. If you click on the *Manufacturer Name* dropdown, it shows you the available manufacturers; that’s also the work of a Python script. ![web app code](/images/posts/whats-code/web-app-code.jpeg) ## Where code “is” Code “runs” on a computer, and gets written in a programming language. When you *run* a program, the computer executes those instructions. Most applications that you’re using – like Gmail – work by having their code constantly run in the background, displaying things and waiting for user instructions. Writing code starts with a **programming language**. Languages are just different ways of expressing the same directions, but they’re all doing the same thing under the hood (give or take a few). The [most popular programming language](https://survey.stackoverflow.co/2023/) in the world is Javascript, followed by HTML/CSS and SQL. The nuances of how to accomplish a particular task in a language are usually referred to as **syntax**; and because languages are so similar, getting basically proficient with a new one can be as simple as learning those details. To get a better sense of what syntax means, let’s take a look at one of the most common logic patterns in code: **a loop**. If you have a group of items (like a shopping list) and you want to look at all of the items in the group, you might loop through them: ``` for item in shopping_list: print(item) ``` This would work in Python, but in Javascript you’d need to change it to: ``` for each (item in shopping_list): console.log(item) ``` See? Pretty much the same pattern, but with slightly different wording. Once you’ve written your code in your desired programming language, you’ve got to *run* that code. In practice, most apps you use will be a combination of different types of code in different languages that accomplish their own tasks: HTML/CSS for web page structure and styling, Javascript for interaction and animations in the browser, and another backend language (Python, Java, C++) for moving data around behind the scenes. Developers sometimes split languages into two broad types: low level and high level. Low level languages like Java and C++ are a bit harder to write, but offer more power and speed if you know what you’re doing. These often require special infrastructure to run, and go through a translator called a compiler. Running a program can be really simple. If you’ve written a program in Python (`my_program.py`), you can run it by typing (`python my_program.py`) into [the command line](/posts/whos-afraid-of-the-cli) (Terminal) on your computer. In practice though, as apps have gotten bigger and more complicated, there are sophisticated ways to deploy and run your code that are a bit more involved than this. ## Code frameworks and packages Your app is unique, sure (except the guy who made *Yo* – wtf man), but most of them are actually pretty similar. Chances are that whatever you’re building, you’ll need to write directions for some of these: - Formatting dates - Making requests to a web server - Generating cryptographic hashes - Creating graphs and plots As people built these, they started to share the code they wrote publicly for everyone else to benefit from (it’s a really nice idea, in theory!). Those are called **frameworks** or **packages** or **libraries** or **modules** (there are more names but I’ll spare you), and they’re the basis of all modern code. There are tons of libraries out there for each of the 4 tasks we outlined above: - *Formatting dates* – [`Moment` (Javascript)](https://momentjs.com/) - *Making requests to a web server* – [`Requests` (Python)](https://requests.readthedocs.io/en/master/) - *Generating cryptographic hashes* – [`Cryptography` (Python)](https://cryptography.io/en/latest/) - *Creating graphs and plots* – [`D3` (Javascript)](https://d3js.org/) Using these modules means that instead of building the code to make a graph from scratch, you can use the code that someone else wrote to do it. Modern apps are *full* of these libraries, and that’s most of what you should think about when you hear **[open source](/posts/whats-open-source)**. Open source just means that the library code is public for everyone to see, and generally also implies some community around improving and maintaining that code. ## Terms and concepts covered ``` Code ``` ``` Programming language ``` ``` Syntax ``` ``` Framework, module, package, library ``` ``` Open source ``` ## Further reading - One of the best ways to understand what code is and how developers work is through data: the [2019 Stack Overflow Developer Survey](https://insights.stackoverflow.com/survey/2019) is a great place to start - Some programming languages have very specific purposes: SQL, for example, is [exclusively for querying a database](https://www.infoworld.com/article/3219795/what-is-sql-the-first-language-of-data-analysis.html) - Learning to code has been in vogue for the past few years, and there are more [online resources to get it done](https://www.codecademy.com/) than you could possibly ever cover in a lifetime