Downloading standard subroutines from the Internet: an example.

• Start a web browser such as Netscape.
• Go to the MAT350 home page, http://www.geneva.edu/~bvds/mat350.
• Go to the Guide to Available Mathematical Software (GAMS)
• Go to "the problem decision tree." You might want to peruse some of the other categories. They will be useful in the future.
• Go to the category "service routines."
• Go to the category "machine dependent constants."
• Choose the routine "d1mach.f" (double precision) from the BLAS library. Also note the routine "r1mach.f" (single precision). You will need this later.
• Now, click on "source" or "fullsource" to download the file containing the subroutine.
• On your browser, find the "Save As..." command in the "File" menu. When saving the file, be sure to save it as a "text" file and not as "html".
• You are now done with the Netscape part of the task.
• Your Microsoft Windows operating system will add a ".txt" extension to the file name. You will have to remove this.
• Before compiling the subroutine, you will want to look at the file with a text editor.
• The instructions for using this routine are somewhat obscure. B is the base of the floating point numbers and T is the number of bits used to hold the mantissa. Thus,

  B**(1-T), THE LARGEST RELATIVE SPACING
  

  is machine epsilon.
• The file contains both FORTRAN and C code. If you are using FORTRAN, you can simply compile the code "as is" since the C code is commented out.
• If you are using C, delete the FORTRAN code. (You might want to retain the instructions by commenting them out.) Then remove the *'s from the first column of each line of the C code as instructed.
• Generally, subroutines that you download from the Internet should be left in a separate file.