What are some alternatives?
When comparing Xcode and Atom, you can also consider the following products
Microsoft Visual Studio - Microsoft Visual Studio is an integrated development environment (IDE) from Microsoft.
Visual Studio Code - Build and debug modern web and cloud applications, by Microsoft
IntelliJ IDEA - Capable and Ergonomic IDE for JVM
Sublime Text - Sublime Text is a sophisticated text editor for code, html and prose - any kind of text file. You'll love the slick user interface and extraordinary features. Fully customizable with macros, and syntax highlighting for most major languages.
Android Studio - Android development environment based on IntelliJ IDEA
Vim - Highly configurable text editor built to enable efficient text editing