SUBROUTINE GBITS(NPACK,ISAM,IBIT,NBITS,NSKIP,ITER)
      DIMENSION NPACK(ITER),ISAM(ITER)
C        THIS ROUTINE IS JUST A REPEATED CALL TO GBIT
C        WHERE SUCCESSIVE CALLS SKIP NSKIP BITS
C        AND THE LOOP COUNT IS ITER
      ISW = 1
      GO TO 10
      ENTRY SBITS(NPACK,ISAM,IBIT,NBITS,NSKIP,ITER)
C        THIS ROUTINE IS JUST A REPEATED CALL TO SBIT
C        WHERE SUCCESSIVE CALLS SKIP NSKIP BITS
C        AND THE LOOP COUNT IS ITER
      ISW = 2
      GO TO 10
      ENTRY GBYTES(NPACK,ISAM,IBIT,NBITS,NSKIP,ITER)
C        THIS ROUTINE IS JUST A REPEATED CALL TO GBYTE
C        WHERE SUCCESSIVE CALLS SKIP NSKIP BITS
C        AND THE LOOP COUNT IS ITER
      ISW = 3
      GO TO 10
      ENTRY SBYTES(NPACK,ISAM,IBIT,NBITS,NSKIP,ITER)
C        THIS ROUTINE IS JUST A REPEATED CALL TO SBYTE
C        WHERE SUCCESSIVE CALLS SKIP NSKIP BITS
C        AND THE LOOP COUNT IS ITER
      ISW = 4
      GOTO 10
      ENTRY G_BYTES(NPACK,ISAM,IBIT,NBITS,NSKIP,ITER)
C        THIS ROUTINE IS JUST A REPEATED CALL TO G_BYTE
C        WHERE SUCCESSIVE CALLS SKIP NSKIP BITS
C        AND THE LOOP COUNT IS ITER
      ISW = 5
      GOTO 10
      ENTRY S_BYTES(NPACK,ISAM,IBIT,NBITS,NSKIP,ITER)
C        THIS ROUTINE IS JUST A REPEATED CALL TO S_BYTE
C        WHERE SUCCESSIVE CALLS SKIP NSKIP BITS
C        AND THE LOOP COUNT IS ITER
      ISW = 6
      GOTO 10
10    IOFF = IBIT
      IBASE = 1
      DO 30 I = 1 , ITER
         GO TO(11,12,13,14,15,16)ISW
11       CALL GBIT(NPACK(IBASE),ISAM(I),IOFF,NBITS)
         GO TO 20
12       CALL SBIT(NPACK(IBASE),ISAM(I),IOFF,NBITS)
         GO TO 20
13       CALL GBYTE(NPACK(IBASE),ISAM(I),IOFF,NBITS)
         GO TO 20
14       CALL SBYTE(NPACK(IBASE),ISAM(I),IOFF,NBITS)
         GO TO 20
15       CALL G_BYTE(NPACK(IBASE),ISAM(I),IOFF,NBITS)
         GOTO 20
16       CALL S_BYTE(NPACK(IBASE),ISAM(I),IOFF,NBITS)
         GOTO 20
20       IOFF = IOFF + NBITS + NSKIP
         IBASE = IBASE + IOFF/32      
         IOFF = MOD(IOFF,32)
30    CONTINUE
      RETURN
      END
      SUBROUTINE GBYTE(NPACK,ISAM,IBIT,NBITS)
C
C     gbyte and sbyte are special routines to do the same
C     things as their counterparts on the Mesa.
C     They differ from the bits routines in that bits
C     are counted from the top of the word rather than
C     the bottom.  This means that the bits they specify jump around
C     when crossing byte boundaries.  There is no assumption
C     made about the wordsize of the machine they were written
C     on.  However the maximum number of bits extracted must be
C     less than or equal to 32.
C
      BYTE NPACK(8)
      INTEGER T
      EXTERNAL SS$_ABORT
      IDBIT(I) = 7 - MOD(I,8)
      ISW = 3
      ISAM = 0
      GO TO 10
      ENTRY SBYTE(NPACK,ISAM,IBIT,NBITS)
      ISW = 4
10    IBASE = IBIT/8
C     ibase points to the first byte involved
      IOFF = IBIT - 8*IBASE
C     ioff is the bit offset within first byte
      M = (IOFF+NBITS-1)/8 + 1
C     m is the number of bytes (including partials) involved
C     IF(M.GT.5)THEN
      IF(NBITS.GT.32)THEN
         TYPE *,'ILLEGAL VALUE FOR NBITS IN S/GBYTE(S) CALL'
         CALL SYS$EXIT(SS$_ABORT)
      END IF
      NN = 0
C     nn is the number of bits transferred
      DO 20 I = M , 1 , -1
C     loop on bytes
         IS = IDBIT(0)
C        calc first bit within byte
         IE = IDBIT(7)
C        calc last bit within byte
         IF(I.EQ.1)IS = IDBIT(IOFF)
C        first bit varies for first byte
         IF(I.EQ.M)IE = IDBIT(IOFF+NBITS-1)
C        last bit varies for last byte
         N = IS - IE + 1
C        calc number of bits within byte to xfer
         IF(ISW.EQ.4)GO TO 12
         CALL GBIT(NPACK(IBASE+I),T,IE,N)
C        extract bits from source
         CALL SBIT(ISAM,T,NN,N)
C        and load into destination
         GO TO 15
12       CALL GBIT(ISAM,T,NN,N)
C        extract bits from source
         CALL SBIT(NPACK(IBASE+I),T,IE,N)
C        and load into destination
15       NN = NN + N
C        update bits xferred
20    CONTINUE
      RETURN
      END
      SUBROUTINE G_BYTE(NPACK,ISAM,IBIT,NBITS)
C
C     g_byte and s_byte are special routines to do the same
C     things as their counterparts on the Mesa.
C     They differ from the bits routines in that bits
C     are counted from the top of the word rather than
C     the bottom.  This means that the bits they specify jump around
C     when crossing byte boundaries.  There is no assumption
C     made about the wordsize of the machine they were written
C     on.  However the maximum number of bits extracted must be
C     less than or equal to 32.
C
      BYTE NPACK(8)
      INTEGER T
      EXTERNAL SS$_ABORT
      IDBIT(I) = 7 - MOD(I,8)
      ISW = 3
      ISAM = 0
      GO TO 10
      ENTRY S_BYTE(NPACK,ISAM,IBIT,NBITS)
      ISW = 4
10    IBASE = IBIT/8
C     ibase points to the first byte involved
      IOFF = IBIT - 8*IBASE
C     ioff is the bit offset within first byte
      M = (IOFF+NBITS-1)/8 + 1
C     m is the number of bytes (including partials) involved
C     IF(M.GT.5)THEN
      IF(NBITS.GT.32)THEN
         TYPE *,'ILLEGAL VALUE FOR NBITS IN S/G_BYTE(S) CALL'
         CALL SYS$EXIT(SS$_ABORT)
      END IF
      NN = 0
C     nn is the number of bits transferred
      DO 20 I = M , 1 , -1
C     loop on bytes
         IBB = IBASE + I - 1
         IBC = IBB/4
         IBD = 4*IBC+3-MOD(IBB,4) + 1
C        calculate unshifted byte
         IS = IDBIT(0)
C        calc first bit within byte
         IE = IDBIT(7)
C        calc last bit within byte
         IF(I.EQ.1)IS = IDBIT(IOFF)
C        first bit varies for first byte
         IF(I.EQ.M)IE = IDBIT(IOFF+NBITS-1)
C        last bit varies for last byte
         N = IS - IE + 1
C        calc number of bits within byte to xfer
         IF(ISW.EQ.4)GO TO 12
C        CALL GBIT(NPACK(IBASE+I),T,IE,N)
         CALL GBIT(NPACK(IBD),T,IE,N)
C        extract bits from source
         CALL SBIT(ISAM,T,NN,N)
C        and load into destination
         GO TO 15
12       CALL GBIT(ISAM,T,NN,N)
C        extract bits from source
C        CALL SBIT(NPACK(IBASE+I),T,IE,N)
         CALL SBIT(NPACK(IBD),T,IE,N)
C        and load into destination
15       NN = NN + N
C        update bits xferred
20    CONTINUE
      RETURN
      END