ed is a POSIX-compliant line editor.  It should work with any regular
expression package that conforms to the POSIX interface standard, such as
GNU regex(3).

The following compiler directives are recognized:
GNU_REGEX	- use with GNU regex(3)
DES		- use to add encryption support (requires crypt(3))
NO_REALLOC_NULL	- use if realloc(3) does not accept a NULL pointer

The file `ed-1003.2' in the ./doc directory describes POSIX ed.  Extensions
to the POSIX standard are described in the file `extensions.'

The ./test directory contains regression tests for ed. The README
file in that directory explains how to run these.

For a description of the ed algorithm, see Kernighan and Pike's book
"Software Tools in Pascal," Addison-Wesley, 1981.