Primes by Trial Division - FORTRAN IV

26 July 2020

No block-form conditionals—single statements only. Output format statement mandatory for TTY.

      INTEGER UNIT, FOUND, COUNT, I, PRIMES(100)

      UNIT  = 4
      FOUND = 0
      COUNT = 2

10    FOUND = FOUND + 1
      WRITE (UNIT,900) COUNT
900   FORMAT (I6)
      PRIMES(FOUND) = COUNT
      COUNT = COUNT + 1

      I = 1
19    IF (FOUND .LT. 100) GOTO 20
      GOTO 30
20      IF (MOD(COUNT,PRIMES(I)) .EQ. 0) GOTO 21
         GOTO 22
21        COUNT = COUNT + 1
          I = 1
          GOTO 20
22      IF (I .EQ. FOUND) GOTO 10
        I = I + 1
        GOTO 19

30    STOP
      END

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