! This is the C run-time start-off routine.  It's job is to take the! arguments as put on the stack by EXEC, and to parse them and set them up the! way _main expects them.! It also initializes _environ when this variable isn't defined by the! programmer.  The detection of whether _environ belong to us is rather! simplistic.  We simply check for some magic value, but there is no other! way..extern _main, _exit, crtso, __penviron, __penvp.extern begtext, begdata, begbss, endtext, enddata, endbss.textbegtext:crtso:	xor	bp, bp			! clear for backtrace of core files	mov	bx, sp	mov	ax, (bx)		! argc	lea	dx, 2(bx)		! argv	lea	cx, 4(bx)	add	cx, ax	add	cx, ax			! envp	! Test if environ is in the initialized data area and is set to our	! magic number.  If so then it is not redefined by the user.	mov	bx, #_environ	cmp	bx, #__edata		! within initialized data?	jae	0f	testb	bl, #1			! aligned?	jnz	0f	cmp	(bx), #0x5353		! is it our environ?	jne	0f	mov	__penviron, bx		! _penviron = &environ;0:	mov	bx, __penviron	mov	(bx), cx		! *_penviron = envp;	push	cx			! push envp	push	dx			! push argv	push	ax			! push argc	call	_main			! main(argc, argv, envp)	push	ax			! push exit status	call	_exit	hlt				! force a trap if exit fails.databegdata:	.data2	0			! for sep I&D: *NULL == 0__penviron:	.data2	__penvp			! Pointer to environ, or hidden pointer.bssbegbss:	.comm	__penvp, 2		! Hidden environment vector