Since address in an MTNL directory is 35-40 characters, a 40X4 LCD was procured for convenience of the user. Controlling a 40X4 LCD is like controlling two 40X2 LCDs. The first two rows and the next two rows are on separate controller. It is connected to the 8051 using an 8255 PPI.

A51 Source code for 40X4 LCD

Some LCD programming tutorials

http://home.iae.nl/lcd0.shtml : A complete reference to LCD interfacing

http://www.8052.com/tutlcd.phtml : LCD tutorial for beginners