Implement int 0x21 AH = 0x02, write character to stdout

src/int21/0.s

@@ -7,9 +7,23 @@
 ; 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
+
+; AH = 0x02
+; write character to stdout
+; inputs:
+; 	DL: character
+; outputs:
+; 	AL: last character output
+wrout:
+	; TODO handle ^C and stuff
+	; TODO handle stdout properly
+	push bx
+	mov al, dl
+	mov bl, 0x70
+	call print_character
+	pop bx
 	ret

src/vga.s

@@ -1,3 +1,20 @@
+; print a character to the screen
+; inputs:
+; 	AL: ASCII character
+; outputs:
+; 	none
+print_character:
+	push ax
+	push bx
+
+	mov ah, 0x0E
+	mov bh, 0x00
+	int 0x10
+
+	pop bx
+	pop ax
+	ret
+
 ; print a string to the screen
 ; inputs:
 ; 	DS:SI: pointer to '$'-terminated string