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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