diff --git a/Source/Doc/SystemGuide.md b/Source/Doc/SystemGuide.md
index a17bbc19..08c5b15c 100644
--- a/Source/Doc/SystemGuide.md
+++ b/Source/Doc/SystemGuide.md
@@ -909,7 +909,9 @@ Returns the current Line Characteristics (DE) of the specified Character
 Returns device information for the specified Character Unit (C).  The 
 status (A) is a standard HBIOS result code.
 
-Device Attribute (C) values are: 0 = RS/232, 1 = Terminal, 2 = Parallel.
+The two high bits of Device Attribute (C) are: 00 = RS/232, 01 = Terminal,
+10 = Parallel.  The remaining bits should be ignored and are used
+internally.
 
 Device Type (D) indicates the specific hardware driver that handles the 
 specified Character Unit.  Values are listed at the start of this 
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index 8733d758..61819807 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -8429,7 +8429,7 @@ PS_SERIAL:
 	CALL	NEWLINE
 	RET
 ;
-; PRINT CHARACTER TYPE (SERIAL ATTRIBUTE IN E)
+; PRINT CHARACTER TYPE (SERIAL ATTRIBUTE IN C)
 ;
 PS_PRTST:
 	LD	HL,PS_STPPT