1GENERAL: do - unconditional or Fortran-77 do-loops

Usage: do [<variable> <start> <end> [<step>]]
         .
         .
       end do

The statement "do" allows for loops within macros. "do" without further
parameters starts an unconditional loop. An unconditional loop can only 
be left by a "break", "return", "exit", or "quit" statement. "do" followed
by parameters starts a Fortran style do-loop where the variable <variable> 
and the integer expressions <start>, <end>, and, optionally, <step> have 
the same meaning as in Fortran-77.

Examples: do
            if (filename.eq.' ') break
            .
            .
          end do

          do i 1 10
            print "Iteration $i."
          end do