title: I am trying to compile following code wrote in fortran but has many errors
body: <p>I am trying to compile this following code in gfortran compiler:</p>
  
  <pre><code>    do_cmd       = .not. is_group
  do while (.not. EOF(unit=100) .and. .not. flag_stop)
      read (100, '(A)', iostat = ios) buf
      if (buf(1:1)=="#") then
          ! comment line
      elseif ((buf(1:2)=="v ") .and. do_cmd) then ! vertex
          read(buf(2:), *, iostat=ios) p(1), p(2), p(3)
          if (ios.ne.0) then
              print "(/,2x,'Error of reading vertex position from obj-file (line #'(I3)');')", line_index
              stop
          end if
  </code></pre>
  
  <p>But I get these errors when the code is compiling:</p>
  
  <pre><code>      do while (.not. EOF(unit=100) .and. .not. flag_stop)
                                1
        Error: Keyword argument requires explicit interface for procedure ‘eof’ at (1)
  </code></pre>
  
  <p>and;</p>
  
  <pre><code>     do while (.not. EOF(unit=100) .and. .not. flag_stop)
                     1
       Error: Function ‘eof’ at (1) has no IMPLICIT type
  </code></pre>
  
  <p>I will be so grateful if anyone could help me.</p>
  
  <p>edit:
  I'm very new in fortran and couldn't find out how eof function works in gfortran.</p>
  
  <p>What does it mean using unit=100 in argument?
  And also Thought it is a logical function by default. How should I implicit its type?</p>