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21 lines
1.1 KiB
Markdown
21 lines
1.1 KiB
Markdown
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# Parts of an Embedded Program
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Open the `beginner/apps` folder in VS Code.
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``` console
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$ # or use "File > Open Folder" in VS Code
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$ code beginner/apps
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```
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Then open the `src/bin/hello.rs` file.
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If you find it more convenient to open the repository at the root then please also add the `beginner/apps` folder to the VS Code workspace: right click the left side panel, select "Add folder to workspace" and add the `beginner/apps` folder.
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Note the differences between this embedded program and a desktop program:
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The `#![no_std]` attribute indicates that the program will not make use of the standard library, `std` crate. Instead it will use the `core` library, a subset of the standard library that does not on a underlying operating system (OS).
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The `#![no_main]` attribute indicates that the program will use a custom entry point instead of the default `fn main() { .. }` one.
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The `#[entry]` attribute declares the custom entry point of the program. The entry point must be a divergent function; note that the return type is the never type `!`. The function is not allowed to return; therefore the program is not allowed to terminate.
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