Liquid Crystal Display:-
An LCD is a low-cost, low power device capable of displaying text and images. LCD's are extremely common in embedded systems since such system often does not have video monitors like those that come standard with desktop systems.
LCD's can be found on numerous common device like watches, copy machine, and calculators.
The basic principle of one type of LCD, a reflective LCD, works as follows, first, incoming light passes through a polarizing plate. Next, that polarized light encounters liquid crystal material.
If we excite a region of this material, we cause the material molecules to align, which in turns causes the polarized light to pass through the material. Otherwise, the light does not pass through.
Finally, light that passed through hits a mirror and reflects back, so the excited region appears to light up.
Another type of LCD, an absorption LCD works similarly but uses a block surface instead of a mirror. The surface below the excited regions absorbs light, thus appearing darker than the other regions.
A dot-matrix LCD consists of a matrix of dots that can display alphanumeric characters (letters and digits) as well as other symbols. A common dot-matrix LCD has five column and eight rows of dots for one character. An LCD driver converts input data into the appropriate electrical signals necessary to excite the appropriate LCD dots.