	SUBROUTINE GSRST(XV,YV,XA,YA)
C
C
	COMMON /GCDPRM/ XS, YS, XT, YT, RCOS, RSIN, VXL, VXH, VYL, VYH
C
C	ROTATE, SCALE, AND THEN TRANSLATE COORDINATES
C	(TAKE VIRT. COORD. INTO SCREEN COORD.)
C
	XTEMP = XV
	XA = XS*(RCOS*XTEMP+RSIN*YV) + XT
	YA = YS*(RCOS*YV-RSIN*XTEMP) + YT
	RETURN
	END

	SUBROUTINE GSIRST(XA,YA,XV,YV)
C
C	INVERSE ROTATE, SCALE, AND THEN TRANSLATE
C	(TAKE ABSOLUTE COORD. INTO VIRTUAL COORD.)
C
	COMMON /GCDPRM/ XS, YS, XT, YT, RCOS, RSIN, VXL, VXH, VYL, VYH
C
C	CONVERT ABSOLUTE CM. COORD. TO VIRTUAL CM. COORDINATES
C
	XTEMP = (XA-XT)/XS
	YV = (YA-YT)/YS
	XV = RCOS*XTEMP-RSIN*YV
	YV = RCOS*YV+RSIN*XTEMP
	RETURN
	END
