Add new under construction system calls to the readme and change the one for loading files to accomodate them, move the disk parameters to the main namespace in anticipation of restructuring the disk operations with the addition of the new system calls, and rewrite parts of system to remove essentially duplicate code.

src/SYSTEM.ASM

@@ -86,12 +86,13 @@ int 0x21
 cmp byte [input], 0x0
 jz shell
 
-;Check for a current drive change command
+;Set SI at the command
 ;Set SI at input
 mov si, input
 ;Ignore leading spaces
 call ignoreleading
-;Check
+
+;Check for a current drive change command
 cmp byte [si + 0x1], ":"
 jne extract
 cmp byte [si + 0x2], 0x0
@@ -101,11 +102,8 @@ je changecurdrive
 
 ;Extract the specification of the program file
 extract:
-;Set SI at input and DI at program
-mov si, input
+;Set DI at program
 mov di, program
-;Ignore leading spaces
-call ignoreleading
 ;Initialise program with spaces
 mov cx, 0xe
 mov al, 0x20
@@ -155,6 +153,13 @@ call ignoreleading
 ;Execute the program
 jmp 0x3000
 
+;Print a command error message and return to the shell
+cmderror:
+mov si, cmderrormsg
+mov ah, 0x2
+int 0x21
+jmp shell
+
 ;Change the current drive
 ;Get the BIOS equipment list
 changecurdrive:
@@ -189,17 +194,10 @@ mov [curdrive], dl
 call setcurdriveletter
 jmp shell
 
-;Print a command error message and return to the shell
-cmderror:
-mov si, cmderrormsg
-mov ah, 0x2
-int 0x21
-jmp shell
-
 ;Welcome message
 welcomemsg db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0x0
 
-;Drive
+;Drive stuff
 curdrive     db 0x0
 driveletters db "AaBbCcDd"