# Uxn A stack-based VM, written in ANSI C. ## Build ``` cc uxn.c -std=c89 -Os -DNDEBUG -g0 -s -Wall -Wno-unknown-pragmas -o uxn ``` ## Assembly Syntax ### Write - `;variable`, set a label to an assigned address - `:const`, set a label to a constant short - `@label`, set a label to an address ### Read - `,literal`, push label value to stack - `.pointer`, read label value ### Special - `( comment )`, toggle parsing on/off - `|0010`, move to position in the program - `"hello`, push literal bytes for word "hello" ``` ;value ( alloc a zero-page variable ) @0010 ( start at page 1 ) ,03 ,02 ADD ,05 EQU ,there ROT JMC :here ( when not equal ) ,ee BRK :there ( when is equal ) ,ff BRK ``` ## Mission ### Assembler - Catch overflow/underflow - Jumps should be relative ### CPU - Pointers/Literals - A Three-Way Decision Routine(http://www.6502.org/tutorials/compare_instructions.html) - Print word to stdout - Draw pixel to screen - Detect mouse click - SDL Layer Emulator - Build PPU - Add flags.. ### Devices - Devices each have an input byte, an output byte and two request bytes. ## Refs https://code.9front.org/hg/plan9front/file/a7f9946e238f/sys/src/games/nes/cpu.c http://www.w3group.de/stable_glossar.html http://www.emulator101.com/6502-addressing-modes.html http://forth.works/8f0c04f616b6c34496eb2141785b4454 https://justinmeiners.github.io/lc3-vm/