Remove file name extensions from commands, implement command tails, ignore extra spaces either leading or trailing a command or between a command and its tail (except for drive changing), and fix a typo in hello.

src/HELLO.ASM

@@ -2,10 +2,10 @@ CPU 8086
 ORG 0x2000
 
 ;Prints a hello world.
-mov si, .hello
+mov si, hello
 mov ah, 0x2
 int 0x21
 int 0x20
 
 ;Data
-.hello db "Hello world!", 0x0
+hello db "Hello world!", 0x0

src/SYSTEM.ASM

@@ -86,20 +86,64 @@ int 0x21
 cmp byte [input], 0x0
 jz shell
 ;Check for a drive change command
-mov si, input + 1
+mov si, input + 0x1
-mov di, driveletter + 1
+mov di, driveletter + 0x1
 call cmpstr
 jnc changedrive
 
-;Load an execute a program
+;Extract the program name
+;Set SI at input and DI at program
+mov si, input
+mov di, program
+;Ignore leading spaces
+call ignoreleading
+;Initialise program with spaces
+mov cx, 0xc
+mov al, 0x20
+rep stosb
+sub di, 0xc
+;Initialise the length counter
+mov bl, 0x8
+extractprog:
+;Load a character
+lodsb
+;Check for the string end
+cmp al, 0x0
+je addext
+;Check for a space
+cmp al, 0x20
+je addext
+;Check for the length limit
+cmp bl, 0x0
+je cmderror
+;Store the character
+stosb
+;Decrease the counter
+dec bl
+jmp extractprog
+;Add extension to the name
+addext:
+push si
+mov si, extension
+mov cx, 0x5
+.loop:
+lodsb
+stosb
+loop .loop
+
+;Load and execute the program
 ;Load
 mov bx, 0x2000
-mov si, input
+;mov si, input
+mov si, program
 mov ah, 0x0
 int 0x22
 ;Check for errors
 cmp al, 0x1
 je cmderror
+;Pass the command tail to the program
+pop si
+call ignoreleading
 ;Execute
 jmp 0x2000
 
@@ -157,13 +201,15 @@ call setdriveletter
 jmp shell
 
 ;Data
+welcomemsg   db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0x0
 drive        db 0x0
 driveletter  db "?:", 0x0
-welcomemsg   db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0x0
 prompt       db "> ", 0x0
-driverrormsg db "Unknown drive", 0x0
-cmderrormsg  db "Unknown command", 0x0
 input        times 0x4c db 0x0
+program      times 0xd db 0x0
+extension    db ".BIN", 0x0
+cmderrormsg  db "Unknown command", 0x0
+driverrormsg db "Unknown drive", 0x0
 crlf         db 0xd, 0xa, 0x0
 
 ;Set the drive letter
@@ -226,6 +272,14 @@ pop bx
 pop ax
 ret
 
+;Ignore leading spaces in the command and its tail
+ignoreleading:
+lodsb
+cmp al, 0x20
+je ignoreleading
+dec si
+ret
+
 ;Print a CRLF
 printcrlf:
 ;Store the initial registers in the stack