https://github.com/amid68/hello-world-in-arm-assembly

A simple "Hello, World!" program written in ARM assembly for macOS
https://github.com/amid68/hello-world-in-arm-assembly

Last synced: 20 days ago
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A simple "Hello, World!" program written in ARM assembly for macOS

• Host: GitHub
• URL: https://github.com/amid68/hello-world-in-arm-assembly
• Owner: Amid68
• License: mit
• Created: 2024-09-04T11:54:48.000Z (almost 2 years ago)
• Default Branch: main
• Last Pushed: 2024-09-04T12:01:19.000Z (almost 2 years ago)
• Last Synced: 2025-01-07T00:38:09.455Z (over 1 year ago)
• Language: Assembly
• Size: 1.95 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# Hello World in ARM Assembly for macOS

This is a simple "Hello, World!" program written in ARM assembly for macOS, targeting ARM64 architecture (like Apple Silicon M1).

## How the Code Works

This program uses the C runtime and calls functions from the standard library (`puts` and `exit`) rather than using direct system calls, which makes it easier and more portable.

### Assembly Code Breakdown

1. **Global Declaration:**

   - The program starts by declaring `_main` as the global entry point using `.globl _main`.

2. **Aligning Code:**

   - The `.p2align 2` ensures that the code is properly aligned in memory.

3. **Main Function (`_main`):**

   - **`ADR X0, helloworld`:** This instruction loads the address of the `helloworld` string into register `X0`, which will be passed to the `puts` function.

   - **`bl _puts`:** The `bl` instruction (branch with link) calls the `puts` function from the C library, which prints the string.

   - **`mov X0, #0`:** After the string is printed, this instruction sets the value `0` in `X0`, which will be the return value of the program. An exit code of 0 is used to indicate success.

   - **`b _exit`:** This branches to the `_exit` function from the C library to terminate the program.

4. **Data Section:**

   - **`helloworld` label:** This label marks the location of the string in memory.

   - **`.asciz "Hello, World!"`:** This directive defines a null-terminated string to be printed.