Move system calls to interrupts and rename the main system loop to shell.

src/ECHO.INC

@@ -5,7 +5,8 @@ echo:
 ;Read a string
 mov di, buffer
 mov al, 0xff
-call readln
+mov ah, 0x3
+int 0x21
 
 ;Check for an empty string
 cmp byte [buffer], 0x0
@@ -13,7 +14,8 @@ je .done
 
 ;Print the string
 mov si, buffer
-call println
+mov ah, 0x2
+int 0x21
 
 .done:
 ret

src/FILEIFY.INC

@@ -5,7 +5,8 @@ fileify:
 ;Read a string
 mov di, buffer
 mov al, 0xff
-call readln
+mov ah, 0x3
+int 0x21
 
 ;Set SI and DI
 mov si, buffer
@@ -50,13 +51,15 @@ jmp .extloop
 .error:
 pop ax
 mov si, .errormsg
-call println
+mov ah, 0x2
+int 0x21
 jmp .done
 
 .print:
 pop ax
 mov si, .file
-call println
+mov ah, 0x2
+int 0x21
 
 .done:
 ret

src/HELLO.INC

@@ -3,8 +3,9 @@
 hello:
 
 mov si, .hello
-call println
+mov ah, 0x2
+int 0x21
 
 ret
 
-.hello db "Hello world!", 0x0
+.hello db "Hello world!", 0x0

src/HELP.INC

@@ -3,7 +3,8 @@
 help:
 
 mov si, .help
-call println
+mov ah, 0x2
+int 0x21
 
 ret
 

src/KEYCODE.INC

@@ -12,7 +12,8 @@ mov [.ascii], al
 
 ;Print the prefix
 mov si, .prefix
-call printstr
+mov ah, 0x0
+int 0x21
 
 ;Convert the scancode to a hex string
 mov al, [.scan]
@@ -27,7 +28,8 @@ call .byte2hex
 
 ;Print the keycode
 mov si, .keycode
-call println
+mov ah, 0x2
+int 0x21
 
 ret
 

src/NEWLINE.INC

@@ -7,7 +7,8 @@ push si
 
 ;Print the newline
 mov si, .newline
-call printstr
+mov ah, 0x0
+int 0x21
 
 ;Load the initial registers from the stack
 pop si

src/PRINTLN.INC

@@ -3,9 +3,10 @@
 println:
 
 ;Print the string
-call printstr
+mov ah, 0x0
+int 0x21
 
 ;Print a newline
 call newline
 
-ret
+iret

src/PRINTSTR.INC

@@ -23,4 +23,4 @@ jmp .loop
 ;Load the initial registers from the stack
 pop ax
 
-ret
+iret

src/READLN.INC

@@ -3,9 +3,10 @@
 readln:
 
 ;Read the string
-call readstr
+mov ah, 0x1
+int 0x21
 
 ;Print a newline
 call newline
 
-ret
+iret

src/READSTR.INC

@@ -129,7 +129,7 @@ pop cx
 pop bx
 pop ax
 
-ret
+iret
 
 ;Move the cursor forward
 

src/SYSTEM.ASM

@@ -3,14 +3,33 @@ ORG 0x500
 
 jmp start
 
-;Calls
+;Interrupt handler
-%include "CMPSTR.INC"
+int0x20:
+jmp shell
+int0x21:
+cmp ah, 0x0
+je printstr
+cmp ah, 0x1
+je readstr
+cmp ah, 0x2
+je println
+cmp ah, 0x3
+je readln
+iret
+int0x22:
+;To do: loading and saving files
+iret
+
+;System calls
 %include "PRINTSTR.INC"
 %include "READSTR.INC"
-%include "NEWLINE.INC"
 %include "PRINTLN.INC"
 %include "READLN.INC"
 
+;Internal calls
+%include "CMPSTR.INC"
+%include "NEWLINE.INC"
+
 ;Commands
 %include "ECHO.INC"
 %include "FILEIFY.INC"
@@ -20,42 +39,61 @@ jmp start
 
 start:
 
+;Setup
 ;Set up the stack
 cli
 mov sp, stack
 add sp, 0x100
 sti
+;Set up the interrupt vectors
+;Interrupt 0x20
+mov ax, int0x20
+mov [0x80], ax
+mov ax, 0x0
+mov [0x82], ax
+;Interrupt 0x21
+mov ax, int0x21
+mov [0x84], ax
+mov ax, 0x0
+mov [0x86], ax
+;Interrupt 0x22
+mov ax, int0x22
+mov [0x88], ax
+mov ax, 0x0
+mov [0x8a], ax
 
 ;Print a welcome message
 mov si, welcomemsg
-call println
+mov ah, 0x2
+int 0x21
 
-loop:
+shell:
 
 ;Prompt for and read a command
 ;Print a prompt
 mov si, prompt
-call printstr
+mov ah, 0x0
+int 0x21
 ;Read a command
 mov di, buffer
 mov al, 0xff
-call readln
+mov ah, 0x3
+int 0x21
 
 ;Identify and execute the command
 exec:
 ;Check for no command
 cmp byte [buffer], 0x0
-je loop
+je shell
 .echo:
 ;Check
 mov si, buffer
 mov di, cmd.echo
 call cmpstr
 jnc .fileify
-;jnc .hello
 ;Execute
 call echo
-jmp loop
+jmp shell
 .fileify:
 ;Check
 mov si, buffer
@@ -64,7 +102,7 @@ call cmpstr
 jnc .hello
 ;Execute
 call fileify
-jmp loop
+jmp shell
 .hello:
 ;Check
 mov si, buffer
@@ -73,7 +111,7 @@ call cmpstr
 jnc .help
 ;Execute
 call hello
-jmp loop
+jmp shell
 .help:
 ;Check
 mov si, buffer
@@ -82,7 +120,7 @@ call cmpstr
 jnc .keycode
 ;Execute
 call help
-jmp loop
+jmp shell
 .keycode:
 ;Check
 mov si, buffer
@@ -91,11 +129,12 @@ call cmpstr
 jnc .error
 ;Execute
 call keycode
-jmp loop
+jmp shell
 .error:
 mov si, errormsg
-call println
+mov ah, 0x2
-jmp loop
+int 0x21
+jmp shell
 
 welcomemsg db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0x0