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Update README.md

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David Schmenk 2014-11-06 10:48:23 -08:00
parent c1240a2cf2
commit 08d56abac3
1 changed files with 6 additions and 4 deletions
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README.md
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@ -133,7 +133,9 @@ The source code of a PLASMA module first defines imports, constants, variables a
word txtscrn[] = $0400,$0480,$0500,$0580,$0600,$0680,$0700,$0780
word[] = $0428,$04A8,$0528,$05A8,$0628,$06A8,$0728,$07A8
word = $0450,$04D0,$0550,$05D0,$0650,$06D0,$0750,$07D0
word[8] txt2scrn = $0800,$0880,$0900,$0980,$0A00,$0A80,$0B00,$0B80
word txt2scrn[8] = $0800,$0880,$0900,$0980,$0A00,$0A80,$0B00,$0B80
word[8] txt2scrna = $0828,$08A8,$0928,$09A8,$0A28,$0AA8,$0B28,$0BA8
word txt2scrnb = $0850,$08D0,$0950,$09D0,$0A50,$0AD0,$0B50,$0BD0
//
// Misc global variables
//
@ -151,7 +153,7 @@ Strings are defined like Pascal strings, a length byte followed by the string ch
//
// An initialized string of 64 characters
//
byte txtfile[64] = "UNTITLED"
byte[64] txtfile = "UNTITLED"
```
Functions are defined after all constants, variables and data. Functions can be forward declared with a *predef* type in the constant and variable declarations. Functions have optional parameters and always return a value. Functions can have their own variable declarations. However, unlike the global declarations, no data can be predeclared, only storage space. There is also a limit of 254 bytes of local storage. Each parameter takes two bytes of local storage, plus two bytes for the previous frame pointer. If a function has no parameters or local variables, no local frame will be created, improving performance. A function can specify a value to return. If no return value is specified, a default of 0 will be returned.
@ -164,7 +166,7 @@ There are four basic types of data that can be manipulated: constants, variables
word hgrscan[] = $2000,$2400,$2800,$2C00,$3000,$3400,$3800,$3C00
word = $2080,$2480,$2880,$2C80,$3080,$3480,$3880,$3C80
hgrscan:[yscan][xscan] = fillval
hgrscan.[yscan][xscan] = fillval
```
Values can be treated as pointers by preceding them with a ‘^’ for byte pointers, ‘*’ for word pointers.
@ -351,7 +353,7 @@ call(aReg, xReg, yReg, statusReg, addr) returns a pointer to a four byte structu
const xreg = 1
const getlin = $FD6A
numchars = (call(0, 0, 0, 0, getlin)).xreg // return char count in X reg
numchars = call(0, 0, 0, 0, getlin).xreg // return char count in X reg
```
syscall(cmd, params) calls ProDOS, returning the status value.