First Program & Build/Run (REPL vs swiftc, scripts)
Write your first Swift program, run it in the REPL, compile with swiftc, and save scripts for reuse.
First Program & Build/Run (REPL vs swiftc, scripts) is a free Swift Academy lesson on CoddyKit. This is lesson 3 of 3. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, and your progress syncs across the web and the CoddyKit app. The Swift Academy course includes 3 lessons in total.
Intro
Goal: Write your first Swift program and learn how to run it. We will use the REPL, compile with swiftc, and create simple scripts.
Hello in REPL
In the REPL, type print("Hello, Swift") and press Enter. The result appears instantly—perfect for fast tests.
Save to file
Create a file hello.swift with a simple program. Files let you reuse and share code beyond the REPL.
hello.swift code
This file hello.swift contains a minimal Swift program you can compile or run.
// Print a simple greeting
print("Hello, Swift from a file!")
// Work with numbers
let a = 2
let b = 3
print("Sum = \(a + b)")
Compile & run
Run swiftc hello.swift -o hello to build an executable. Then ./hello runs the program natively.
Script mode
You can also run scripts directly: swift hello.swift. It interprets line by line, slower than compiled output but handy for quick runs.
Compilation question
Quick check: Which command compiles a Swift file into an executable binary?
Recap
Recap: Try code in REPL, save to .swift files, compile with swiftc, or run as scripts. Now you can build and run your own Swift programs.
Learn Swift with an AI tutor — free
Write and run real code in your browser, get instant help from a 24/7 AI tutor, and pick up where you left off on the web or in the app.
- Courses
- 122
- Lessons
- 409
Frequently Asked Questions
Is the “First Program & Build/Run (REPL vs swiftc, scripts)” lesson free?
Yes — any 3 lessons of the Swift Academy learning path, including “First Program & Build/Run (REPL vs swiftc, scripts)”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Swift Academy course includes 3 lessons in total.
What will I learn in “First Program & Build/Run (REPL vs swiftc, scripts)”?
Write your first Swift program, run it in the REPL, compile with swiftc, and save scripts for reuse. You practise Swift Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Swift Academy?
No prior experience is required. Swift Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 3 of 3.
How long does the “First Program & Build/Run (REPL vs swiftc, scripts)” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Swift Academy lesson?
Yes. Every Swift Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- What is Swift? Safety, Performance, Readability
- Install & Tools: Swift toolchain, REPL, swiftc, Editors
- First Program & Build/Run (REPL vs swiftc, scripts)