Day 17

Directories

	Today, we will investigate what goes into creating and deleting a directory (folder).

Creating
	To create a directory, we use Function 39h of the DOS Service Interrupt 21h.
Function 39h expects a pointer to a NULL-terminated string in DX. 

	Here's a small program to create an "Elmo" directory:

	;;---CODE START---;;
		mov ah,39h
		mov dx,offset dirname
		int 21h
		mov ah,4Ch
		int 21h

		dirname db "Elmo",0
	;;---CODE END---;;

Deleting
	Deleting is identical and is Function 3Ah. This will delete the directory
created by the previous program:

	;;---CODE START---;;
		mov ah,3Ah   ; different function this time.
		mov dx,offset dirname
		int 21h
		mov ah,4Ch
		int 21h

		dirname db "Elmo",0
	;;---CODE END---;;

This Day In Review

	I should take this opportunity to mention that Function numbers always go in AH or all of AX!
And each function expects it's parameters in specific registers, if you put things in the wrong register
the code will not work.

	I wonder files are next...
		- GbaGuy


Intro - Day 18