Organize int 21h handlers into separate files

Makefile

@@ -1,9 +1,8 @@
 TARGET = foxdos
 
 FILES = config.s \
-		src/int21.s \
-		src/kernel.s \
-		src/vga.s
+		$(wildcard src/*.s) \
+		$(wildcard src/int21/*.s)
 
 .PHONY: all qemu clean
 all: obj/boot.o obj/kernel.o $(TARGET)

src/int21/0.s

@@ -0,0 +1,15 @@
+; 0x00 - 0x0F
+
+; AH = 01h
+; read a character from stdin and print it to stdout
+; inputs:
+; 	none
+; outputs:
+; 	AL: character read from stdin
+rdin_echo:
+	push ax
+	mov ah, 8
+	int 0x21
+	; TODO does echo go to stdout or to screen?
+	pop ax
+	ret

src/int21/2.s

@@ -0,0 +1,89 @@
+; 0x20 - 0x2F
+
+; AH = 25h
+; set interrupt vector
+; inputs:
+; 	AL: interrupt number
+; 	DS:DX: new interrupt handler
+; outputs:
+; 	none
+setint:
+	pusha
+	xor ah, ah
+	shl ax, 2
+	mov di, ax
+	xor ax, ax
+	push es
+	mov es, ax
+	mov word es:[di], dx
+	mov word es:[di+2], ds
+	pop es
+	popa
+	ret
+
+; AH = 2ch
+; read system time from the CMOS
+; inputs:
+; 	none
+; outputs:
+; 	CH: hours
+; 	CL: minutes
+; 	DH: seconds
+gettime:
+	push ax
+	xor dl, dl
+
+	mov al, dl ; seconds
+	call rdcmos
+	mov dh, al
+
+	mov al, 2h ; minutes
+	call rdcmos
+	mov cl, al
+
+	mov al, 4h ; hours
+	call rdcmos
+	mov ch, al
+
+	shl al, 1 ; adjust for 12 hour time
+	jnc .end
+	add ch, 12
+
+.end:	pop ax
+	ret
+
+; AH = 2dh
+; set system time in the CMOS
+; inputs:
+; 	CH: hours
+; 	CL: minutes
+; 	DH: seconds
+; outputs:
+; 	none
+settime:
+	push bx
+	mov bl, ch
+	mov bh, 0x4
+	call wrcmos
+	mov bl, cl
+	shr bh, 1
+	call wrcmos
+	mov bl, dh
+	cmp dl, 50 ; rtc cannot hold hundredths of a second so we round
+	jng .f
+	inc bl
+.f:	xor bh, bh
+	call wrcmos
+	xor al, al ; it probably succeeded, its fine. TODO: am i missing return codes anywhere else
+	pop bx
+	ret
+
+; AH = 2eh
+; set disk verify flag
+; inputs:
+; 	AL: 0 if off, 1 if on
+; outputs:
+; 	none
+setverify:
+	mov [verify], al
+	ret

src/int21/3.s

@@ -0,0 +1,36 @@
+; 0x30 - 0x3F
+
+; AH = 30h
+; get the DOS version number
+; inputs:
+; 	none
+; outputs:
+; 	AL: major version
+; 	AH: minor version
+getver:
+	mov ax, 8 ; if it is not zero indexed this indicates windows ME
+	xor bx, bx ; update: what does that comment mean
+	mov cx, bx
+	ret
+
+; AH = 35h
+; get interrupt vector
+; inputs:
+; 	AL: interrupt number
+; outputs:
+; 	ES:BX: current interrupt handler
+getint:
+	push ds
+	push di
+	push ax
+	xor ah, ah
+	shl ax, 2
+	mov di, ax
+	xor ax, ax
+	mov ds, ax
+	pop ax
+	mov word bx, [di]
+	mov word es, [di+2]
+	pop di
+	pop ds
+	ret

src/int21/4.s

@@ -0,0 +1,13 @@
+; 0x40 - 0x4F
+
+; AH = 4dh
+; get return code
+; inputs:
+; 	none
+; outputs:
+; 	AH: termination type (0 = normal, 1 = control-C abort, 2 = critical error abort, 3 = terminate and stay resident)
+; 	AL: return code
+getret:
+	xor ax, ax
+	xchg [retcode], ax
+	ret

src/int21/5.s

@@ -0,0 +1,11 @@
+; 0x50 - 0x5F
+
+; AH = 54h
+; get disk verify flag
+; inputs:
+; 	none
+; outputs:
+; 	AL: 0 if off, 1 if on
+getverify:
+	mov al, [verify]
+	ret

src/int21/int21.s

@@ -45,107 +45,11 @@ tmp: dw 0
 retcode: dw 0
 verify: db 0
 
-; AH = 01h
-; read a character from stdin and print it to stdout
-; inputs:
-; 	none
-; outputs:
-; 	AL: character read from stdin
-rdin_echo:
-	push ax
-	mov ah, 8
-	int 0x21
-	; TODO does echo go to stdout or to screen?
-	pop ax
-	
-; AH = 4dh
-; get return code
-; inputs:
-; 	none
-; outputs:
-; 	AH: termination type (0 = normal, 1 = control-C abort, 2 = critical error abort, 3 = terminate and stay resident)
-; 	AL: return code
-getret:
-	xor ax, ax
-	xchg [retcode], ax
-	ret
-
-; AH = 30h
-; get the DOS version number
-; inputs:
-; 	none
-; outputs:
-; 	AL: major version
-; 	AH: minor version
-getver:
-	mov ax, 8 ; if it is not zero indexed this indicates windows ME
-	xor bx, bx ; update: what does that comment mean
-	mov cx, bx
-	ret
-
-
-; AH = 54h
-; get disk verify flag
-; inputs:
-; 	none
-; outputs:
-; 	AL: 0 if off, 1 if on
-getverify:
-	mov al, [verify]
-	ret
-
-; AH = 2eh
-; set disk verify flag
-; inputs:
-; 	AL: 0 if off, 1 if on
-; outputs:
-; 	none
-setverify:
-	mov [verify], al
-	ret
-
-; AH = 35h
-; get interrupt vector
-; inputs:
-; 	AL: interrupt number
-; outputs:
-; 	ES:BX: current interrupt handler
-getint:
-	push ds
-	push di
-	push ax
-	xor ah, ah
-	shl ax, 2
-	mov di, ax
-	xor ax, ax
-	mov ds, ax
-	pop ax
-	mov word bx, [di]
-	mov word es, [di+2]
-	pop di
-	pop ds
-	ret
-
-; AH = 25h
-; set interrupt vector
-; inputs:
-; 	AL: interrupt number
-; 	DS:DX: new interrupt handler
-; outputs:
-; 	none
-setint:
-	pusha
-	xor ah, ah
-	shl ax, 2
-	mov di, ax
-	xor ax, ax
-	push es
-	mov es, ax
-	mov word es:[di], dx
-	mov word es:[di+2], ds
-	pop es
-	popa
-	ret
+%include "int21/0.s"
+%include "int21/2.s"
+%include "int21/3.s"
+%include "int21/4.s"
+%include "int21/5.s"
 
 ; read from CMOS register
 ; inputs:
@@ -186,60 +90,3 @@ wrcmos:
 	pop ax
 	sti
 	ret
-
-; AH = 2ch
-; read system time from the CMOS
-; inputs:
-; 	none
-; outputs:
-; 	CH: hours
-; 	CL: minutes
-; 	DH: seconds
-gettime:
-	push ax
-	xor dl, dl
-
-	mov al, dl ; seconds
-	call rdcmos
-	mov dh, al
-
-	mov al, 2h ; minutes
-	call rdcmos
-	mov cl, al
-
-	mov al, 4h ; hours
-	call rdcmos
-	mov ch, al
-
-	shl al, 1 ; adjust for 12 hour time
-	jnc .end
-	add ch, 12
-
-.end:	pop ax
-	ret
-
-; AH = 2dh
-; set system time in the CMOS
-; inputs:
-; 	CH: hours
-; 	CL: minutes
-; 	DH: seconds
-; outputs:
-; 	none
-settime:
-	push bx
-	mov bl, ch
-	mov bh, 0x4
-	call wrcmos
-	mov bl, cl
-	shr bh, 1
-	call wrcmos
-	mov bl, dh
-	cmp dl, 50 ; rtc cannot hold hundredths of a second so we round
-	jng .f
-	inc bl
-.f:	xor bh, bh
-	call wrcmos
-	xor al, al ; it probably succeeded, its fine. TODO: am i missing return codes anywhere else
-	pop bx
-	ret

src/kernel.s

@@ -2,7 +2,7 @@
 
 kjmp: ; MUST be a short jump due to loader config
 	jmp kernel_entry
-%include "int21.s"
+%include "int21/int21.s"
 
 kernel_entry:
 	mov si, hello_string