PC Compatible Mode

In this Mode, the Plus/4 and C-16 keyboards acts like a standard PC Keyboard, keeping the original layout as far as possible, but also remapping non-existent ones to modern functions.

Considering the C-264 Series had no Numeric KeyPad, nor complete set of Function Keys (F1 a F12),  the paradigm is similar to “60%” Keyboards, using Commodore key as Special Function Keys (Fn) allowing the same key having more than one function.

In the following pic, the PC Mode layout is shown for Plus/4 and C-16. This is the mode when you plug your keyboard on. 

You can see colored keys having different assignments than the original C-264 Keyboards, as described below.

Plus/4 Keyboard
C-16 Keyboard


  • RUN/STOP turns to Left ALT.
  • CLEAR/HOME is Backspace.
  • ESCAPE is also ~  (diacritic) if SHIFT is held.
  • £ turns to \ (inverted slash), o | (pipe) if SHIFT is held.
  • 0 key is also ^ (circumflex accent) if SHIFT is held.
  •  (Minus) is also _ (underscore) if SHIFT is held.
  • HELP/F7 Key turns to F4.

The rest of the exclusive C-264 keys: @ (at),  * (asterisk),  = (equal) and + (add) will work as such, regardless SHIFT being held or not.

LEFT CONTROL and TAB in one key.

This is maybe one of the coolest feature of QMK Firmware. Due to the fact that the CONTROL key is located ijn the same place than TAB in a regular PC Keyboard, Keymmodore-264 implements a dual role fot this key:

If you tap it (meaning press and release without pressing another key) it will work as a TAB; however if you press and hold, and press another key, it will work as a CONTROL allowing the combination with other keys, like CTRL+C, CTRL+V, etc. Cool uh?


The Left SHIFT work like any standard PC Keyboard, allowing access to capital letters and additional characters as usual. Right SHIFT are interpreted as Left SHIFT also because are wired as one by the keyboard matrix.  

The SHIFT LOCK key is actually the same than the Left SHIFT, but with a mechanical lock so it is not the same than a real CAPS LOCK, affecting also the 0 a 9 keys.

COMMODORE (C=) key as “Fn” key

The key with  the C= symbol on it, generally called «Commodore Key», works as a Modification Fn key allowing to access to a different layers and function like the “60%” Style Keyboards.

In the following diagram you can see in white which keys will change its function when Fn  (C=) is pressed. Some functions are already in the legends of the keys, and others are added to better productivity.

Plus/4 Keyboard
C-16 Keyboard
  • 1 to 0 keys, as well as + y will work as F1 to F12. 
  • DEL key works as INSERT as the top legend.
  • andcursor keys work as PAGE UP y PAGE DOWN respectively.
  • ← and cursor keys work as HOME and END respectively.
  • ESC key works as ` (grave tilde), and ~ (diacritic).
  • : (colon) and ; (semicolon) work as { and } (brackets) respectively.
  • P key works as PRINT SCREEN.
  • * (asterisk) key works enabling and disabling NUM LOCK  (very important for joysticks).
  • HELP works as F7 (useful for BMC64 emulator)
  • < (less than) y (greater than) decrease and increase audio volume respectively (*).
  • / (slash) mutes the audio output (*).
  • C fires the Calculator (*).

(*) If supported by the Operative System.

Switching to Emulator Compatibility Modes.

Pressing C= Key with F1, F2 or F3 switch to different Emulators layouts depending what computer you want to emulate: 

  • C-64, VIC-20, 16, 116 and Plus/4 Mode: Keep Fn (C=) pressed and press F1.
  • C-128 Mode: Keep Fn (C=) pressed and press F2.
  • PET Graphics Keyboard: Keep Fn (C=) pressed and press F3.
    • PET Business Keyboard: Once you have switched to Graphics Keyboard, you can switch to Business Keyboard by pressing again Fn (C=) and F3.

To avoid any confussion, it is not possible to switch between two Emulator Modes (except Graphics to Business in PET) . You have to switch back to PC Compatible Mode first by pressing C= and CONTROL. Also remember you need the configuration keyboard layout files for your emulator to work properly.