Add first steps of another assembler attempt

com/a86.asm

@@ -0,0 +1,58 @@
+		org 0x100
+
+		mov ax, 0x3D00
+		mov dx, infile
+		int 0x21
+		jc err
+
+		mov [fd], ax
+
+loop:		call getc
+		jc end
+		cmp dl, 26
+		je end
+		mov ah, 2
+		int 0x21
+		jmp loop
+
+end:		ret
+
+err:		mov dx, ax
+
+dumpdx:		; setup bx and ah for int 10h call
+		xor bx, bx
+		mov ah, 0x0e
+		mov cl, 4
+		; this double-call is essentially a 4 times repeating loop
+		call dmpdx1
+dmpdx1:		call dmpdx2
+dmpdx2:		; grab highest nibble from dx
+		mov al, dh
+		; remove highest nibble from dx
+		shl dx, cl
+		; shift away second-highest nibble that we accidentally copied
+		shr al, cl
+		; map 0-9 to ascii codes for '0' to '9'
+		add al, 0x30
+		; if result is larger than '9', ...
+		cmp al, 0x3a
+		jl dmpdx3
+		; ... add 7 so we continue at 'A'
+		add al, 7
+dmpdx3:		int 0x10
+		ret
+
+		; read a character from the input file into DL
+getc:		mov dl, 26
+		push dx
+		mov ah, 0x3f
+		mov bx, [fd]
+		mov cx, 1
+		mov dx, sp
+		int 0x21
+		pop dx
+		ret
+
+infile:		db "com/a86.asm", 0
+
+fd:		dw 0