How to use KEY_LEFTSHIFT in BB-black with 4x4 matrix keyboard? How does this key work?

Hi Folks,

I am working on a project that uses Debian on Beaglebone-black Rev-C. I have to interface a 4x4 matrix keyboard over GPIOs with Beaglebone-black. One of the key is suppose to be KEY_LEFTSHIFT. Can somebody explain how this Key works, KEY_LEFTSHIFT. It will ease the development.

Many thanks in advance.