[ DOCS ] : EXOS Kernal Documentation
Note: Instructions translated from https://www.c64-wiki.de/wiki/V-DOS
Early EXOS and clones may be PAL-only. They can be modified to work on NTSC systems by editing the binary directly:
Search for:
ad 00 dd 4a 4a ea ea
Replace with:
ad 00 dd 4a 4a c1 ea
Function key assignment
To make the C64 easier to use, the most important DOS commands are stored on the function keys.
- F1 = LIST ↵
- F2 = SYS 32768↵ (module start $8000)
- F3 = RUN :↵
- F4 = SYS 4096*12 (stands for $C000 (49152), can be overwritten)
- F5 = LOAD “
- F6 = SAVE “
- F7 = LOAD”$”,8↵ (Display of the directory without data loss! The directory system routine is modified accordingly by V-DOS)
- F8 = CLOSE 7: OPEN 7,8,15,” (for entering floppy commands)
Note: The BASIC commands are called in the abbreviated version; ↵ The command is executed immediately by a CHR$(13).
Access via LOAD and SAVE using the function keys refers to the currently connected floppy disk drive. If a is ,8:not added, the file is loaded to the saved memory address (ie with LOAD”Program”,8,1:).
Operating system commands
- CTRL + D = Display the directory without data loss (not available in all versions!)
- CTRL + K = Read error channel
- CTRL + O = OLD ( save program after reset or NEW )
- CTRL + U = Save programs longer than 151 blocks (enter before the SAVE command)
- CTRL + A = Turn off fast charger
- CTRL + X = List BASIC program starting from the last edited program line
- CTRL + Z = List BASIC program starting 50 lines before the last used program line
- CTRL + F = Increase the frequency of the read/write head. This speeds up DOS commands
- CTRL + Reset button = Performs a reset and bypasses any reset protection or module start
POKE 0, PEEK (0) OR 128 RETURN = Disables function key assignment
RAM-Floppy
The V-DOS module provides a 20kB RAM floppy disk that can be used for BASIC programs. Smaller BASIC programs can be stored in this RAM floppy disk and then called up again from there, which can be particularly useful when programming in BASIC. The RAM floppy disk can be used either completely or in three areas of different sizes. Only one program can be stored in each area.
| Area | Size | memory address |
| 0 | 20k | $B0-$FF |
| 1 | 4k | $B0-$BF |
| 2 | 4k | $C0-$CF |
| 3 | 12k | $D0-$FF |
Note: Areas 1, 2, 3 cannot be used simultaneously with area 0, because area 0 corresponds to the entire RAM floppy and thus areas 1, 2 and 3 together.
Operating the RAM floppy disk:
Calling up the selection menu for
- CTRL + W = Save
- CTRL + L = Load
- CTRL + V = Exchange programs from main memory and selected RAM floppy area
In the selection menu that then appears, the desired memory area must be selected using the number key.
Additional screen memory
The V-DOS module manages a total of four different screen memories ($A000 to $AFFF; 40960 to 45055). Screen contents can be stored in these screen memories and then retrieved from there. This function is particularly useful if certain masks or program sequences are used frequently.
- CTRL + F1 = Store or recall screen memory 1
- CTRL + F3 = Store or recall screen memory 2
- CTRL + F5 = Store or recall screen memory 3
- CTRL + F7 = Store or recall screen memory 4
After switching on the C64, all four screen memories are filled with random characters. When using the above key combinations, the current screen content is always swapped
with the content of the corresponding screen memory .
If you want to access the screen memory and copy the contents of the screen or screen memory , i.e. not swap them, you should use the following key combinations:
- C= + F7 = Reading screen memory 4
- C= + F1 = Store in screen memory 3
- C= + F3 = Store in screen memory 4
- C= + F5 = Reading screen memory 3
