C     CALCULATE PRIME PAIRS UP TO A GIVEN LIMIT
C     A PRIME PAIR IS A PAIR OF PRIMES SEPARATED BY 2
C
      DIMENSION N(4000),NN(5),MM(5)
      NP=0
      NNP=0
      WRITE(4,100)
  100 FORMAT(' MAXIMUM PRIME SEARCHED FOR? ',)
      READ(4,101)MAX
  101 FORMAT(I6)
      WRITE(4,102)MAX
  102 FORMAT(' SEARCHING FOR PRIME PAIRS UP TO AND INCLUDING',I6)MAX
      DO 1 I=3,MAX-2,2
      IF (J.EQ.0) GOTO 2
      DO 3 J=1,NP
      IF ((I/N(J))*N(J) .EQ. I) GOTO 1
    3 CONTINUE
C     I IS A PRIME - ADD TO LIST
C     CHECK FOR STORAGE OVERFLOW (PREVENT F4 CRASH)
C
      IF(NP .EQ. 4000) GOTO 10
    2 NP=NP+1
      N(NP)=I
      II=I+2
      DO 4 J=1,NP
      IF((II/N(J))*N(J) .EQ. II) GOTO 1
    4 CONTINUE
C     BOTH I AND I+2 ARE PRIME, PRINT THEM
C     FOR COMPACTNESS PRINT AS AN ARRAY 5 PAIRS WIDE
C
    5 NNP=NNP+1
      NN(NNP)=I
      MM(NNP)=II
      IF(NNP.NE.5)GOTO 1
      NNP=0
      WRITE(4,103)(NN(J),MM(J),J=1,5)
  103 FORMAT(5(' ('I5,',',I5,'), '))
    1 CONTINUE
C     FLUSH THE OUTPUT BUFFER
C
   11 IF(NNP .NE. 0) WRITE(4,103)(NN(J),MM(J),J=1,NNP)
C     PRINT A TABLE OF PRIMES FOUND
C
      WRITE(4,200)
  200 FORMAT('0LIST OF PRIME NUMBERS CALCULATED:')
      WRITE(4,300)(N(J),J=1,NP)
  300 FORMAT(10(' 'I5,', '))
      STOP
   10 WRITE(4,201)
  201 FORMAT(' STORAGE FOR PRIMES EXHAUSTED')
      GOTO 11