constant iBUFSIZE 500

function main(string filename)
  fsfileinputstream fpi
  integer e, i, aval, zval
  string s, buf, c
  set chars

  e = 0
  fpi =@ fsfileinputstream.new(filename, error=e)
  if fpi =@= .nul
    s = "Error, file """ + filename + """ not found{d}{a}"
  else
    chars =@ set.new()
    aval = .charval("a")
    zval = .charval("z")
    buf = .lcase(fpi.getstring(iBUFSIZE, 1))
    while not fpi.endofdata and buf > ""
      i = 1
      while i <= .len(buf)
        c = .substr(buf, i, 1)
        if .charval(c) >= aval and .charval(c) <= zval
          chars.addvalue(c)
        end if
        i = i + 1
      end while
      buf = .lcase(fpi.getstring(iBUFSIZE, 1))
    end while

    s = "Character counts for """ + filename + """{d}{a}"
    i = 1
    while i <= chars.count()
      s = s + chars[i] + ": " + .tostr(chars.valuecount(chars[i]), 10) + "{d}{a}"
      i = i + 1
    end while
  end if
end function s