Added some meat to the README

README.md

@@ -1,2 +1,79 @@
 # ProDOS-Utils
 File management utilities for the ProDOS operating system on the Apple II
+
+## Sortdir
+
+*Sortdir* is a powerful utility for managing ProDOS directories.  It provides
+a number of functions, all of which may be applied to an individual directory,
+a directory tree or an entire volume:
+
+  - Checking directory integrity and making repairs
+  - Multi-level directory sort
+  - Manipulating the case of filenames *
+  - Manipulating the format of time and date information *
+  - Zeroing free blocks
+
+*Sortdir* is intended to help users migrate to the new ProDOS 2.5 release,
+which is currently in alpha.  The code has been testing with ProDOS 2.5a8,
+but should run on older versions of ProDOS.  The features marked with an
+asterix (\*) above allow directory entries to be converted from the legacy
+format to the new ProDOS 2.5 format, and vice versa.
+
+ProDOS 2.5 releases may be obtained [here](https://prodos8.com/releases/prodos-25/)
+
+### System Requirements
+
+*Sortdir* requires an enhanced Apple //e, //c or IIgs with 128KB of memory.
+It should run on all versions of ProDOS, but is intended for use with
+ProDOS 2.5.
+
+### Quickstart - Test Disk Image
+
+Download the disk image `sortdir.po`.  This is a bootable 143KB (Disk \]\[)
+ProDOS 2.5 disk image which includes `SORTDIR.SYSTEM`, ready-to-run.
+
+### Build Instructions
+
+If you want to build *Sortdir* (and perhaps contribute to the code!), you
+will require the `cc65` C cross compiler for 6502.  `cc65` can be found
+[here](https://github.com/cc65/cc65).
+
+I also use [Cadius](https://github.com/lroathe/cadius) for copying
+`sortdir.system#ff0000` to an Apple II disk image.
+
+On a Linux system, you should be able to build by simply invoking `make`.
+
+### User Interface
+
+TODO
+
+### Command Line Options
+
+TODO
+
+### Directory Check and Repair
+
+TODO
+
+### Directory Sort
+
+TODO
+
+### Filename Case Change
+
+TODO
+
+### Date and Time Format
+
+This allows the format of the modification time and creation time fields in
+ProDOS directories to be converted from the legacy ProDOS format (ProDOS <2.5)
+to the new date and time formats introduced in ProDOS 2.5.  These new formats
+extend the range of dates that may be represented, in a backwards-compatible
+manner.  *Sortdir* also allows conversion from the new ProDOS 2.5 date and
+time format back to the legacy format.
+
+### Zeroing Free Blocks
+
+Not yet implemented in ProDOS-8 version.
+
+