proc switch:
	local file1$(128),file2$(128),line%,c%
	local from$(7),to$(7)
	local handle1%,handle2%,ret%,mode%,txt$(255),address%
	file1$="\opl\*.opl"
	file2$="\opl\trans.opl"
	dinit "Translate opl version"
	dfile file1$,"From",64
	dchoice c%,"Translate to","S3a,S3Classic"
	dfile file2$,"To",1
	if dialog
		mode%=$0400 or $0020 or $0000
		ret%=ioopen(handle1%,file1$,mode%)
		if ret%<0
			showerr:(ret%)
		endif
		mode%=$0100 or $0020 or $0001
		ret%=ioopen(handle2%,file2$,mode%)
		if ret%<0
			showerr:(ret%)
		endif
		address%=addr(txt$)
		line%=0
		while 1
			gat 20,20
			gprintb "Line "+num$(line%,10),200
			ret%=ioread(handle1%,address%+1,255)
			if ret%<0
				if (ret%<>-36) rem eof condition
					showerr:(ret%)
				else
					break
				endif
			endif
			pokeb address%,ret%
			if (c%=1)
				from$="s3z"
				to$="s3a"
			elseif (c%=2)
				from$="s3a"
				to$="s3z"
			endif
			if (left$(txt$,7)="rem "+to$)
				txt$=right$(txt$,len(txt$)-7)+" rem "+to$
			elseif (right$(txt$,8)=" rem "+from$)
				txt$="rem "+from$+left$(txt$,len(txt$)-8)
			endif
			ret%=iowrite(handle2%,address%+1,len(txt$))
			if ret%<0
				showerr:(ret%)
			endif
			line%=line%+1
		endwh
		ret%=ioclose(handle1%)
		if ret%
			showerr:(ret%)
		endif
		ret%=ioclose(handle2%)
		if ret%
			showerr:(ret%)
		endif
	endif
endp

proc showerr:(val%)
	print "Error",val%,err$(val%)
	get
endp