Assignment 4: Fortran

Fortran
The GNU Fortran compiler, g77, has been installed on all Sun workstations (i.e., flat-rock, hendersonville, marshall, and brevard) as well as the Linux boxes.
To run the compiler simply type "g77" at the command line prompt.
Below is a list of on-line Fortran 77 resources that you may find helpful in working your assignment.
Your Assignment
1. Part 1: An Introduction
  
  Type (or cut and paste) the following program into a file. The file name should end in the extension ".f". Next, compile the program using the g77 compiler. If any compiler errors are reported, edit the program and fix them and repeat until you get a clean compilation.
```
Program Demo
implicit none

" This program generates a table of the square roots of integers
" in a user-specified range.

integer*2 start, finish, i

" ----------------------------------------------Prompt and Input
print*, "Enter the range (two integers) ..."
read*, start, finish

" ----------------------------------------------Validation & Processing
if (start .GT. finish) then
   print*, "Invalid: the start must be less than the end value!"
else if (start .LT. 0) then
   print*, "Invalid: the range must not have negative values!"
else
   do i = start, finish
      write(*,*) i, sqrt(i*1.)
   end do
end if

" ----------------------------------------------
end
```
  Questions
  1. When run, the program prompts you to specify a range of positive integers by entering two integers, being the beginning and end of the range. You can enter the two end-points by separating them by a space or a comma or by pressing ENTER. Try: 1,20 and examine the output.
  2. Re-run the program and test invalid ranges; e.g. -10, 10 or 10,2. Note how the program ends with an error message even though its code flows "smoothly"; without end statements in the middle of it.
  3. The argument of the square root function looks strange: Why did we have to mutiply i by 1? Experiment with this.
  4. Add the following statement before the prompt but after declarations:
    open (unit=50, file='demo.log') but prefix the file name by an appropriate path; e.g. 'c:\demo.log'. Furthermore, change the first asterisk in the write statement (inside the loop) to 50. These changes cause the output of the write statement to be redirected: Instead of appearing on the screen, it goes to the named disk file. Verify this by viewing the generated demo.log file.
  5. Modify the program so that it does not generate any output for integers that are multiples of 5. For example, if the range is 1 to 18, then no lines will be printed for 5, 10 nor 15.
  What to turn in
  Transfer your modified (as described in Questions 4 and 5 above) program to your ftp directory for this class.
2. Part 2: Writing a program
  
  A scientist is interested in the behavior of the function y = f(x), in the range x=1 to x=3. The function does not have a closed-form formula but is an infinite sum of terms with the following pattern:
  
  Develop a FORTRAN program which computes this sum for a given value of x (a real*4 variable). Your program should keep adding terms until the absolute value of the term to be added becomes less than 1.E-4. To test your program, supply the value x = 2.5 and insure that the computed value of y is about 0.22.
  What to turn in
  Transfer your program to your ftp directory for this class.

Assignment 4: Fortran

Part 1: An Introduction

Questions

What to turn in

Part 2: Writing a program

What to turn in