2017-10-20 04:57:30 +02:00
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# Architecture
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RETRO has a multilayer design.
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2017-10-22 20:39:45 +02:00
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At the heart of the system is a virtual machine called Nga. This emulates
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a 32-bit stack processor with a MISC based instruction set.
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2017-10-20 04:57:30 +02:00
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2017-10-22 20:39:45 +02:00
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The core RETRO language is stored as a memory image for Nga. The *image
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file* contains this and is loaded on startup. It holds all of the compiled
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words and data and interacts with Nga.
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2017-10-20 04:57:30 +02:00
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2017-10-22 20:39:45 +02:00
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The third layer is the user interface. RETRO doesn't specify any required
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I/O other than a console log capable of receiving a single character at a
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time. Each host system can implement this and any additional desired I/O
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by extending Nga.
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2017-10-20 04:57:30 +02:00
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# Specifics
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2017-10-22 20:39:45 +02:00
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On iOS the user interface is setup around an editor and an output area.
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The editor extracts code from fenced regions, splits it into tokens
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(elements separated by whitespace) and passes each of these into RETRO
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for processing. After the tokens are processed, the console is updated.
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2017-10-20 04:57:30 +02:00
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2017-10-22 20:39:45 +02:00
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The iOS code provides additional I/O functionality. In the `file:`
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namespace there are words for creating and using files. There's a
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`pb:` vocabulary for interacting with the clipboard. And a `clock:`
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namespace which provides access to the system time and date. These
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are mapped to higher opcodes outside of the core set used by Nga.
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