# Commodore 64 Quick Reference

## Memory map overview

| Range | Meaning |
|---:|---|
| `$0000-$00FF` | Page zero: BASIC/KERNAL workspace, pointers, fast addressing |
| `$0100-$01FF` | Processor stack |
| `$0200-$03FF` | System workspace, buffers, vectors |
| `$0400-$07E7` | Default screen RAM |
| `$07F8-$07FF` | Default sprite pointers |
| `$0801` | Default BASIC program start |
| `$A000-$BFFF` | BASIC ROM, RAM underneath |
| `$C000-$CFFF` | Free RAM often used for ML routines |
| `$D000-$DFFF` | I/O, color RAM, character ROM, or RAM depending on banking |
| `$E000-$FFFF` | KERNAL ROM, RAM underneath |

## Common addresses

| Dec | Hex | Name |
|---:|---:|---|
| 1 | `$0001` | 6510 memory banking port |
| 43 | `$002B` | BASIC start pointer low |
| 44 | `$002C` | BASIC start pointer high |
| 55 | `$0037` | BASIC top pointer low |
| 56 | `$0038` | BASIC top pointer high |
| 198 | `$00C6` | Keyboard buffer count |
| 646 | `$0286` | Current text color |
| 780 | `$030C` | SYS A register save/pass |
| 781 | `$030D` | SYS X register save/pass |
| 782 | `$030E` | SYS Y register save/pass |
| 783 | `$030F` | SYS status save/pass |
| 788 | `$0314` | IRQ vector low |
| 789 | `$0315` | IRQ vector high |
| 792 | `$0318` | NMI vector low |
| 793 | `$0319` | NMI vector high |
| 1024 | `$0400` | Screen RAM |
| 2040 | `$07F8` | Sprite pointer 0 |
| 49152 | `$C000` | Common ML start |
| 53248 | `$D000` | VIC-II base |
| 53280 | `$D020` | Border color |
| 53281 | `$D021` | Background color |
| 54272 | `$D400` | SID base |
| 55296 | `$D800` | Color RAM |
| 56320 | `$DC00` | CIA #1 base |
| 56576 | `$DD00` | CIA #2 base |

## KERNAL jump table

| Hex | Routine | Purpose |
|---:|---|---|
| `$FF81` | CINT | Initialize screen editor |
| `$FF84` | IOINIT | Initialize I/O |
| `$FF87` | RAMTAS | RAM test/init |
| `$FF8A` | RESTOR | Restore vectors |
| `$FF8D` | VECTOR | Read/set vectors |
| `$FF90` | SETMSG | Set system message flag |
| `$FF93` | SECOND | Send secondary address after LISTEN |
| `$FF96` | TKSA | Send secondary address after TALK |
| `$FF99` | MEMTOP | Read/set top of memory |
| `$FF9C` | MEMBOT | Read/set bottom of memory |
| `$FF9F` | SCNKEY | Scan keyboard |
| `$FFA2` | SETTMO | Set timeout |
| `$FFA5` | ACPTR | Read serial byte |
| `$FFA8` | CIOUT | Write serial byte |
| `$FFAB` | UNTLK | Untalk |
| `$FFAE` | UNLSN | Unlisten |
| `$FFB1` | LISTEN | Listen |
| `$FFB4` | TALK | Talk |
| `$FFB7` | READST | Read status |
| `$FFBA` | SETLFS | Set logical file/device/secondary address |
| `$FFBD` | SETNAM | Set filename |
| `$FFC0` | OPEN | Open file |
| `$FFC3` | CLOSE | Close file |
| `$FFC6` | CHKIN | Set input channel |
| `$FFC9` | CHKOUT | Set output channel |
| `$FFCC` | CLRCHN | Restore default I/O |
| `$FFCF` | CHRIN | Input character |
| `$FFD2` | CHROUT | Output character |
| `$FFD5` | LOAD | Load from device |
| `$FFD8` | SAVE | Save to device |
| `$FFDB` | SETTIM | Set clock |
| `$FFDE` | RDTIM | Read clock |
| `$FFE1` | STOP | Check STOP key |
| `$FFE4` | GETIN | Get input character |
| `$FFE7` | CLALL | Close all files |
| `$FFEA` | UDTIM | Update clock |
| `$FFED` | SCREEN | Get screen dimensions |
| `$FFF0` | PLOT | Read/set cursor position |
| `$FFF3` | IOBASE | Return I/O base |

## Color codes

| Code | Color |
|---:|---|
| 0 | Black |
| 1 | White |
| 2 | Red |
| 3 | Cyan |
| 4 | Purple |
| 5 | Green |
| 6 | Blue |
| 7 | Yellow |
| 8 | Orange |
| 9 | Brown |
| 10 | Light red |
| 11 | Dark gray |
| 12 | Gray |
| 13 | Light green |
| 14 | Light blue |
| 15 | Light gray |

## BASIC snippets

```basic
REM BORDER AND BACKGROUND
POKE 53280,6:POKE 53281,0

REM PUT "A" AT UPPER LEFT AND COLOR IT RED
POKE 1024,1:POKE 55296,2

REM CALL MACHINE LANGUAGE AT $C000
SYS 49152
```