Swapped the names of \"a\" and \"b\" to make it more clear what gets processed first, and to make special opcodes not have only a b value. Added a very basic interrupt handler Outlined some hardware detection basics Made the text 80 characters wide because 80's Implemented ALL of following:
DCPU-16 Spec Suggestions =======================
1. Evaluate b before a ---------------------------------------------- This makes instructions that address the stack twice meaningful instead of confusing and useless.
`ADD PEEK, POP` *should* pop the top of the stack and add it to the second entry, but currently the `PEEK` is evaluated before the `POP` occurs.
2. Add [SP+next word] addressing ---------------------------------------------- This makes writing functions that store extra variables or arguments on the stack easier.
POP isn't useful as an a value, and PUSH isn't useful as a b value, so they should be combined into one value, with postincrement and predecrement determined by whether they're in a/b.
3. Make opcodes 5 bits -------------------------------- A literal a value is not very useful, and having 2x more opcodes is very useful. bbbbbbaaaaaaoooo becomes bbbbbbaaaaaooooo
4. Make literal range include -1. ----------------------------------- Shift the literal range from [0, 31] to [-1, 30].
Having -1 as a literal lets you useful one-word instructions like: ``` NEG X --> MUL X, -1 NOT X --> XOR X, -1```
5. Rename O register to EX or OV ------------------------------------- O and 0 are very easy to confuse, other special registers are two characters, and it doesn't always represent overflow.
6. Add signed MUL/DIV instructions -------------------------------------- Signed operations make maneuvers, targeting, and fixed-point trigonometry routines more efficient.
Suggested mnemonics: `MLI`, `DVI`.
7. Add signed right shift (ASR) ----------------------------------------- Signed operations are useful.
8. Add additional IF instructions ------------------------------------ Supporting all the relations (<, >, <=, >=) will make assembly easier to write and read. Suggested mnemonics and effects:
0x11: IFB a, b - performs next instruction only if (a&b)!=0 (Bit set) 0x12: IFE a, b - performs next instruction only if a==b (Equal) 0x13: IFN a, b - performs next instruction only if a!=b (Not equal) 0x14: IFG a, b - performs next instruction only if a>b (signed) (Greater) 0x15: IFA a, b - performs next instruction only if a>b (unsigned) (Above) 0x16: IFL a, b - performs next instruction only if a<b (signed) (Less) 0x17: IFU a, b - performs next instruction only if a<b (unsigned) (Under)
Appendix A. =========== 1. Fix line drawing characters ------------------------------ As [jecowa noted on reddit](http://www.reddit.com/r/dcpu16/comments/sio8u/dcpu_font_help_what_are_those_first_30ish_glyphs/c4ekx9u), you can't make full boxes with the current line drawing characters.
