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Fortran 77 test programs by ntz11397

VIEWS: 6 PAGES: 8

									Fortran 77 Exercise


    Hsiu-Pin Chen
   January 4th, 2007
Exercise : Calculate the value of pi

• Objective: Computing the value of pi by
  integrating the function f(x) = 4 / (1 + x2) from
  x=0 to 1:
                      1
               Π = ∫ f(x)dx
                      0
         How to compute it:
• By summing up the area of
each rectangular, we can get
the value of pi.
                                                   f(x)
• For each rectangular, the      f(x)

area is f(x)*(1/n), where n is
the number of intervals.
                                        0.5/n   (n-0.5)/n x
             Your tasks
1.Read the value of the number of
  intervals (n) from keyboard.
2. Write a double precision function
  which computes f(x) for you.
3. For i=1 to n, x equals to (i-0.5).
   sum = sum + f(x)
4. Multiply the summation by (1/n).
5. Print the value of pi on the screen.
                      Hints
1. Use text editor “pico” to open a file called
   “pi.f”
2. Remember you can only start writing your
   code from the 7th column.
3. The first line starts as follows:
  program Cal_pi
                Hints
Program Cal_pi

  implicit none
  double precision pi,h,sum,x,f
  integer n,I

  Calculation


end



double precision function f(a)
   double precision a
   Calculation
  return
  end
Did you do it right?
   Program Cal_pi
      implicit none
      double precision pi,h,sum,x,f
      integer n,i
      print*, "Enter the number of intervals"
      read*,n
      if (n .le. 0) goto 10
      h = 1.0d0/n
      sum = 0.0d0
      do i =1,n
          x = h * (dble(i) - 0.5d0)
          sum = sum + f(x)
      enddo
      pi = h * sum
      print*," pi is approximately: ", pi
   10    stop
    end
Thank you for your attention!!

								
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