V6/usr/source/salloc/getch.s

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.globl	getchar
.globl	lookchar
.globl	w, r, a, l
/
/
/	routine to read next character from string
/	pointer to by r1; character returned in r0
/	c-bit set if character not availiable (eof)
/
/	mov	...,r1
/	jsr	pc,getchar
/	movb	r0,...
/
getchar:
	jsr	pc,lookchar
	bes	1f
	inc	r(r1)
	tst	r0
1:	rts	pc