C- READ 1024 BYTES AT A TIME.
C- READ INTO ARRAY COMMON WITH 256 REAL*4, 256 INT*4, 1 BYTE STRINGS
C- PICK OUT THE VALUES FOR A CCP4 DENSITY MAP, BE THEY CHARACTER, INTEGER,
C- OR REAL (DENSITIES ARE REAL). 

	CHARACTER*1 BLINE(1024) 
	CHARACTER*36 RECLINE(30)
	EQUIVALENCE (RECLINE(1),BLINE(1))
	real*4 rline(256),TCELL(6),CELL(6)
	EQUIVALENCE (RLINE(1),BLINE(1)),(TCELL(1),RLINE(11))
	INTEGER*4 LINT(256)
	EQUIVALENCE (LINT(1),BLINE(1))
	CHARACTER*80 TTITLE,TITLE,TSYMTRY,SYMTRY
	EQUIVALENCE (TTITLE,RLINE(57))
	EQUIVALENCE (TSYMTRY,RLINE(1))
	CHARACTER*50 INFILE,OUTFILE,FILENAME
	DIMENSION RMAP(400,400)
	WRITE(6,1000)
1000	FORMAT(//' PROGRAM T READ CCP4 MAP FILES')
5	WRITE(6,1100)
1100	FORMAT(/'$Input filename (CR to quit):  ')
	READ(5,1200) INFILE
1200	FORMAT(A)
C	IF (INFILE(:5).EQ.'     ') STOP
C	  INQUIRE(FILE=INFILE, NAME=FILENAME,EXIST=EFLG)
C	  IF (.NOT.EFLG) GOTO 5

       OPEN (UNIT=2,FILE=INFILE,STATUS='OLD',FORM='UNFORMATTED')
       OPEN (UNIT=3,FILE='ENVEL.MAP',STATUS='NEW',FORM='UNFORMATTED',
     & RECL=256, RECORDTYPE='FIXED', CARRIAGECONTROL='NONE')
	READ(2)(RLINE(I),I=1,256)
	WRITE(3)(RLINE(I),I=1,256)
	NFAST=LINT(1)
	NMED=LINT(2)
	NSLOW=LINT(3)
C	(NORIEN IS A GUESS)
	NORIEN=LINT(4)
   	DO 290 I=1,6
290	CELL(I)=TCELL(I)
        NX=LINT(8)
	NY=LINT(9)
	NZ=LINT(10)
	RMYST=RLINE(55)
	TITLE=TTITLE
	WRITE(6,*)'NFAST, MEDIUM, SLOW=',NFAST,NMED,NSLOW
	WRITE(6,*)'MAPTYPE=',NORIEN
	WRITE(6,*)'CELL: ',(CELL(I),I=1,6)
	WRITE(6,*)'NX, NY, NZ=',NX, NY, NZ
        WRITE(6,*)'DENSITY STDDEV=',RMYST
	WRITE(6,*) TITLE

	READ(2)(RLINE(I),I=1,256)
	SYMTRY=TSYMTRY
	WRITE(6,*)SYMTRY
	WRITE(6,*)'Enter THRESHOLD density for envelope:'
	read(5,*) THRESH
C	WRITE(6,*)'ENTER 1 FOR DELAY BETWEEN SECTIONS, 0 FOR NO DELAY'
C	READ(5,*)IDELAY

	  DO 296 IJ=21,256
	    IF (RLINE(IJ).GT.THRESH) THEN
	      RLINE(IJ)=1
	    ELSE
	      RLINE(IJ)=0
	    ENDIF
296	    CONTINUE
        WRITE(3)(RLINE(I),I=1,256)
	
        II=21
	DO 325 I=1,NSLOW
C	WRITE(6,*)
	WRITE(6,*)'SECTION ',I
	DO 300 J=1,NMED
	DO 300 K=1,NFAST
	IF (II.GT.256) THEN
	  READ(2,END=900)(RLINE(IJ),IJ=1,256)
	  DO 298 IJ=1,256
	    IF (RLINE(IJ).GT.THRESH) THEN
	      RLINE(IJ)=1
	    ELSE
	      RLINE(IJ)=0
	    ENDIF
298	    CONTINUE
          WRITE(3)(RLINE(IJ),IJ=1,256)
	  II=1
	  ENDIF
	RMAP(J,K)=RLINE(II)
300	II=II+1
325	CONTINUE

380	CLOSE(UNIT=2)
	CLOSE(UNIT=3)   
	STOP 'NORMAL END'
900	STOP 'END OF FILE BEFORE END OF MAP'
	END