Documentation of kernel API

doc/syscalls.md

@@ -60,7 +60,7 @@ Arguments:
     C: 0x03
 
 Return Values:
-    C: Character value
+    C: Character value or NULL
 
 This call does direct (raw) console input; if there is a character ready, it
 will be read, and if not, NULL will be returned.
@@ -72,7 +72,7 @@ Arguments:
     X: Character value
 
 Return Values:
-    C: Character value
+    None
 
 This call does direct (raw) console output; the value supplied will be treated
 as the value to write to screen memory, and will not be interpreted for terminal
@@ -99,7 +99,7 @@ Arguments:
     Y: Address of buffer (23:16)
 
 Return values:
-    C: Error code
+    C: Status code
 
 This call will read up to 255 characters from stdin, or up to the first newline,
 whichever comes first. While taking input, a simple line editor is presented to
@@ -118,7 +118,7 @@ Return Values:
     C: Status Code
 
 This call checks stdin for a character to read. If there is none, this call will return
-zero in A; if there is a character ready, it will return nonzero in A.
+zero in C; if there is a character ready, it will return nonzero in C.
 
 ## 0x08: Return Version Number
 
@@ -224,8 +224,9 @@ This call attempts to open the file referred to by the provided NULL-terminated
 string, which must contain a fully-qualified pathname -- something of the form
 `[drive]:/[dir]/[dir2]/filename.ext`, such as `sd0:/games/kaboom/readme.ansi`.
 
-If the file is successfully opened, the carry flag will be cleared and the C
-accumulator will contain the file handle. On error, the carry flag will be 
+If the file is successfully opened, the C accumulator will contain the file handle,
+a positive integer value. On error, the C accumulator will contain a negative value,
+indicating an error has occured. 
 
 ## 0x0E: Close File
 
@@ -234,12 +235,11 @@ Arguments:
     X: File handle
 
 Return Values: 
-    C: Error code
+    C: Status code
 
 This call attempts to close the file referred to by the provided file handle.
-On success, the carry flag will be cleared, and the C accumulator will contain
-a status code of 0x0000. On error, the carry flag will be set, and the C
-accumulator will contain an error code.
+On success, the C accumulator will contain a status code of STATUS_OK. On error, 
+the C accumulator will contain a negative value, indicating an error has occured.
 
 ## 0x0F: Duplicate File Handle
 
@@ -248,10 +248,11 @@ Arguments:
     X: File handle
 
 Return Values: 
-    C: File handle or error code
+    C: Status code
+    X: Duplicate of file handle
 
 This call attempts to duplicate the provided file handle. The new file handle
 will be exactly identical to the provided one, and either may be used at any time.
-On success, the carry flag will be cleared, and the C accumulator will contain
-the duplicate file handle. On error, the carry flag will be set, and the C
-accumulator will contain an error code.
+On success, the C accumulator will contain a status code of STATUS_OK, and the X
+register will contain the duplicate file handle. On error, the C accumulator will 
+contain a negative value, indicating an error has occured.