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 — lesson 3 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Swift Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.
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.
Frequently asked questions
Is the “First Program & Build/Run (REPL vs swiftc, scripts)” lesson free?
Yes — the full text of “First Program & Build/Run (REPL vs swiftc, scripts)” is free to read here on the web, and the Swift Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Swift Academy course, upgrade to CoddyKit PRO.
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; this is — lesson 3 of 3, so you can start here or from the beginning and move at your own pace.
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)