Documentation of kernel API

doc/syscalls.md

@@ -225,4 +225,33 @@ 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 
+accumulator will contain the file handle. On error, the carry flag will be 
+
+## 0x0E: Close File
+
+Arguments:
+    C: 0x0E
+    X: File handle
+
+Return Values: 
+    C: Error 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.
+
+## 0x0F: Duplicate File Handle
+
+Arguments:
+    C: 0x0F
+    X: File handle
+
+Return Values: 
+    C: File handle or error code
+
+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.