INT 50 - PC Thuis Organizer Shell - READ FILE

	AX = 0004h
	ES:BX -> buffer for data
	CX = number of bytes to read or 0000h for entire file
	DL = file type
	    01h setting shell
	    02h setting sterm
	    03h INT21 file
	DS:SI -> filename
Return: AX = status
	    0000h successful
	    FFFFh error
Note:	file type numbers are maintained by John Vanderaart; if a new file type
	  is needed, a type number should be requested from him through the
	  magazine:
		PC Thuis BV
		Spaarne 55
		2011 CE HAARLEM
		The Netherlands
SeeAlso: AX=0003h"Shell"