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David Schmenk 2014-04-29 20:27:29 -07:00
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PLASMA/README.md
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@ -143,8 +143,8 @@ After functions are defined, the main code for the module follows. There is no
There are four basic types of data that can be manipulated: constants, variables, addresses, and functions. Memory can only be read or written as either a byte or a word. Bytes are unsigned 8 bit quantities, words are signed 16 bit quantities. Everything on the evaluation stack is treated as a word. Other than that, any value can be treated as a pointer, address, function, character, integer, etc. There are convenience operations in PLASMA to easily manipulate addresses and expressions as pointers, arrays, structures, functions, or combinations thereof. If a variable is declared as a byte, it can be accessed as a simple, single dimension byte array by using brackets to indicate the offset. Any expression can calculate the indexed offset. A word variable can be accessed as a word array in the same fashion. In order to access expressions or constants as arrays, a type identifier has to be inserted before the brackets. a ‘.’ character denotes a byte type, a ‘:’ character denotes a word type. Along with brackets to calculate an indexed offset, a constant can be used after the ‘.’ or ‘:’ and will be added to the base address. The constant can be a defined const to allow for structure style syntax. If the offset is a known constant, using the constant offset is a much more efficient way to address the elements over an array index. Multidimensional arrays are treated as arrays of array pointers. Multiple brackets can follow the ‘.’ or ‘:’ type identifier, but all but the last index will be treated as a pointer to an array.
```
word hgrscan[] = [$2000,$2400,$2800,$2C00,$3000,$3400,$3800,$3C00]
word = [$2080,$2480,$2880,$2C80,$3080,$3480,$3880,$3C80]
word hgrscan[] = $2000,$2400,$2800,$2C00,$3000,$3400,$3800,$3C00
word = $2080,$2480,$2880,$2C80,$3080,$3480,$3880,$3C80
hgrscan:[yscan][xscan] = fillval
```