diff --git a/README.md b/README.md
index 2bf3727..d31cea0 100644
--- a/README.md
+++ b/README.md
@@ -35,14 +35,54 @@ 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`](https://github.com/cc65/cc65) C cross compiler for 6502.
+will require the [`cc65`](https://github.com/cc65/cc65) C cross compiler for
+6502.
 
 I also use [Cadius](https://github.com/mach-kernel/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
+### How to Run `SORTDIR.SYSTEM`
+
+`SORTDIR.SYSTEM` is a ProDOS system file, which means it loads at address
+$2000.  It is possible to launch this program using any application or
+utility that can launch ProDOS systm files, such as Bitsy Bye, which is
+included with ProDOS 2.5.
+
+It is also possible to start the program from the ProDOS `BASIC.SYSTEM`
+prompt, using the normal syntax `-/PATH/TO/SORTDIR.SYSTEM`.  Since the volume
+name of the disk image provided is `/P8.2.5`, the following command can be
+used to start the program: `-/P8.2.5/SORTDIR.SYSTEM`.
+
+When launching `SORTDIR.SYSTEM` from the BASIC prompt it is also possible to
+specify command line parameters.  See below for more information.  If no
+command line options are provided then *Sortdir* will present an interactive
+user interface.
+
+If *Sortdir* is started from a launcher other than `BASIC.SYSTEM`, there is
+no way to pass command line options, so the interactive user interface will
+be used.
+
+Because *Sortdir* uses all of the system memory it reboots the system on
+exit.  (It is not possible to return to BASIC because the workspace has been
+overwritten.)
+
+### Interactive User Interface
+
+![](/Screenshots/Interactive.png)
+
+TODO
+
+### Command Line Options
+
+![](/Screenshots/BASIC_Launch.png)
+
+TODO
+
+### Understading the Display
+
+![](/Screenshots/Running.png)
 
 TODO
 
@@ -78,3 +118,29 @@ time format back to the legacy format.
 Not yet implemented in ProDOS-8 version.
 
 
+### 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.
+
+
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