V5/usr/source/s4/open.s

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including files from this version of Unix. 
/ C library -- open

/ file = open(string, mode)
/
/ file == -1 means error

.globl	_open, retrn, cerror

_open:
	mov	r5,-(sp)
	mov	sp,r5
	mov	4(r5),0f
	mov	6(r5),0f+2
	sys	0; 9f
	bec	1f
	jmp	cerror
1:
	jmp	retrn
.data
9:
	sys	open; 0:..; ..