System Guide Doc Fix

- See discussion at <https://groups.google.com/g/rc2014-z80/c/TIQv8-q4R2s>

ReadMe.md

@@ -7,7 +7,7 @@
 **RomWBW Introduction** \
 Version 3.5 \
 Wayne Warthen  ([wwarthen@gmail.com](mailto:wwarthen@gmail.com)) \
-17 Apr 2025
+24 Apr 2025
 
 # Overview
 

ReadMe.txt

@@ -1,6 +1,6 @@
 RomWBW Introduction
 Wayne Warthen (wwarthen@gmail.com)
-17 Apr 2025
+24 Apr 2025
 
 
 

Source/Doc/SystemGuide.md

@@ -2054,12 +2054,16 @@ standard HBIOS result code.
 |                                        | E: Keycode                             |
 
 Read the next key data from keyboard of the specified Video Unit (C). If
-a keyboard buffer is used, return the next key code in the buffer. If 
+a keyboard buffer is used, return the next Keycode in the buffer. If 
 no key data is available, this function will wait indefinitely for a 
 keypress.  The Status (A) is a standard HBIOS result code.
 
 The Scancode (C) value is the raw scancode from the keyboard for the 
-keypress. Scancodes are from the PS/2 scancode set 2 standard.
+keypress. Scancodes are optional and may not be implemented by the
+driver.  The Scancode values are driver dependent.  In the case of a
+PS/2 keyboard driver, they should be the PS/2 scancode.  Other keyboard
+drivers may return values appropriate for their specific keyboard.  If
+the driver does not implement this, it should return 0 in C.
 
 The Keystate (D) is a bitmap representing the value of all modifier keys
 and shift states as they existed at the time of the keystroke. The 
@@ -2076,6 +2080,9 @@ bitmap is defined as:
 | 1       | Control key was held down        |
 | 0       | Shift key was held down          |
 
+Not all of these bits may be relevant for all keyboards.  Any bit that
+is not relevant should be returned as 0.
+
 The Keycode (E) is generally returned as appropriate ASCII values, if 
 possible. Special keys, like function keys and arrows, are returned as 
 reserved codes as described at the start of this section.