You got error message "procedure entry point in cygreadline6.dll" when you run Cygwin.

Cygwin is a Linux-like environment for Windows. It consists of two parts:
- A DLL (cygwin1.dll) which acts as a Linux API emulation layer providing substantial Linux API functionality.
- A collection of tools which provide Linux look and feel.

The Cygwin DLL currently works with all recent, commercially released x86 32 bit and 64 bit versions of Windows, with the exception of Windows CE.

How to install cygreadline6.dll file?

1. Press Start and select Run
2. Type CMD and press Enter (or if you use Windows ME, type COMMAND)
3. Type regsvr32 cygreadline6.dll and press Enter
4. In the end, you should receive a message saying that your file was successfully installed or uninstalled.