1 files changed, 7 insertions, 2 deletions
diff --git a/io.s b/io.s
index 7b63f95..6968aa4 100644
--- a/io.s
+++ b/io.s
@@ -26,7 +26,9 @@ printchr:
  ; Subroutine: getchr
  ;
  ; Read ATASCII character from keyboard, return in A, without
- ; preserving registers.
+ ; preserving registers. On return, Y = 1 on success. On error,
+ ; Y will contain the error number (probably 128 for Break key or
+ ; 136 for EOF). Note that getchrx does NOT return the error code in Y!
  ;
  ; Uses the published and immutable KEYBDV address in the ROM, meaning
  ; it (a) doesn't require an IOCB open to the K: device, and (b)
@@ -111,12 +113,15 @@ printchrx:
  ; Actually, the return value here is also in Y, if you can think of a
  ; use for that.
  ;
+ ; Note: The CIO error code is NOT returned in Y! Use getchr if you
+ ; need that.
+ ;
  ; Calls getchr.
  ;
 getchrx:
  txa          ; save X,
  pha          ;   on stack.
- jsr getchr     ; get the character.
+ jsr getchr   ; get the character.
  tay          ; save A (our return value).
  pla          ; restore X,
  tax          ;   from stack.