CPU 8086
ORG 0x3000

;Load a file and print it

;Set the stack
cli
mov sp, stack + 0x100
sti

;Check for an empty tail
;Check
cmp byte [si], 0x0
jne start
;Print an error message and abort if the tail is empty
mov si, errormsg
mov ah, 0x2
int 0x21
je done

start:

;Find the end of the filename and add a null if needed
;Set DI at the tail
mov di, si
findend:
;Check for the string end
cmp byte [di], 0x0
je load
;Check for a space
cmp byte [di], 0x20
je addnull
inc di
jmp findend
addnull:
mov al, 0x0
stosb

;Load the file
load:
;Load
mov bx, stack + 0x100
mov ah, 0x0
int 0x22
;Check for errors
cmp al, 0x0
jne done

;Print the file
;Setup
mov bh, 0x0
mov bl, 0x18
mov dl, 0x50
mov si, stack + 0x100
print:
;Decrease the character counter
dec dl
;Load the current character
lodsb
;Print the character
mov ah, 0xe
int 0x10
;Check for a hard line end
cmp al, 0xa
je linecount
;Check for a soft line end
cmp dl, 0x0
je linecount
contprint:
;Check paging
cmp bl, 0x0
jz page
;Repeat for the next character
loop print
jmp done
;Decrease the line counter and reset the character one
linecount:
dec bl
mov dl, 0x50
jmp contprint
;Page
page:
push ax
mov ah, 0x0
int 0x16
pop ax
mov bl, 0x18
mov dl, 0x50
loop print

done:
int 0x20

;Data
errormsg db "File not found", 0x0

stack: