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Merge pull request #8 from orthographic-pedant/spell_check/auxiliary

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Fixed typographical error, changed auxilliary to auxiliary in README.
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Peter Ferrie 2015-09-28 22:43:35 -07:00
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README.md
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@ -21,7 +21,7 @@ A simple compiler was written so that higher level constructs could be used and
One of the goals of PLASMA was to allow for intermixing of functions implemented as bytecode, or native code. Taking a page from the FORTH play book, a function call is implemented as a native subroutine call to an address. If the function is in bytecode, the first thing it does is call back into the interpreter to execute the following bytecode (or a pointer to the bytecode). Function call parameters are pushed onto the evaluation stack in order they are written. The first operation inside of the function call is to pull the parameters off the evaluation stack and put them in local frame storage. Function callers and callees must agree on the number of parameters to avoid stack underflow/overflow. All functions return a value on the evaluation stack regardless of it being used or not.
The bytecode interpreter is capable of executing code in main memory or banked/extended memory, increasing the available code space and relieving pressure on the limited 64K of addressable data memory. In the Apple IIe with 64K expansion card, the IIc, and the IIgs, there is an auxilliary memory that swaps in and out for the main memory in chunks. The interpreter resides in the Language Card memory area that can easily swap in and out the $0200 to $BFFF memory bank. The module loader will move the bytecode into the auxilliary memory and fix up the entrypoints to reflect the bytecode location. The Apple /// has a sophisticated extended addressing architecture where bytecode is located and interpreted.
The bytecode interpreter is capable of executing code in main memory or banked/extended memory, increasing the available code space and relieving pressure on the limited 64K of addressable data memory. In the Apple IIe with 64K expansion card, the IIc, and the IIgs, there is an auxiliary memory that swaps in and out for the main memory in chunks. The interpreter resides in the Language Card memory area that can easily swap in and out the $0200 to $BFFF memory bank. The module loader will move the bytecode into the auxiliary memory and fix up the entrypoints to reflect the bytecode location. The Apple /// has a sophisticated extended addressing architecture where bytecode is located and interpreted.
Lastly, PLASMA is not a typed language. Just like assembly, any value can represent a character, integer, or address. It's the programmer's job to know the type. Only bytes and words are known to PLASMA. Bytes are unsigned 8 bit quantities, words are signed 16 bit quantities. All stack operations involve 16 bits of precision.