Information theory is a branch of applied mathematics and electrical engineering involving the quantification of information. Information theory was developed by Claude E. Shannon to find fundamental limits on signal processing operations such as compressing data and on reliably storing and communicating data. Since its inception it has broadened to find applications in many other areas, including statistical inference, natural language processing, cryptography generally, networks other than communication networks — as in neurobiology,[1] the evolution[2] and function[3] of molecular codes, model selection[4] in ecology, thermal physics,[5] quantum computing, plagiarism detection[6] and other forms of data analysis.[7]
The main concepts of information theory can be grasped by considering the most widespread means of human communication: language. Two important aspects of a concise language are as follows: First, the most common words (e.g., "a", "the", "I") should be shorter than less common words (e.g., "benefit", "generation", "mediocre"), so that sentences will not be too long. Such a tradeoff in word length is analogous to data compression and is the essential aspect of source coding. Second, if part of a sentence is unheard or misheard due to noise — e.g., a passing car — the listener should still be able to glean the meaning of the underlying message. Such robustness is as essential for an electronic communication system as it is for a language; properly building such robustness into communications is done by channel coding. Source coding and channel coding are the fundamental concerns of information theory.
Note that these concerns have nothing to do with the importance of messages. For example, a platitude such as "Thank you; come again" takes about as long to say or write as the urgent plea, "Call an ambulance!" while the latter may be more important and more meaningful in many contexts. Information theory, however, does not consider message importance or meaning, as these are matters of the quality of data rather than the quantity and readability of data, the latter of which is determined solely by probabilities.
Information theory is generally considered to have been founded in 1948 by Claude Shannon in his seminal work, "A Mathematical Theory of Communication". The central paradigm of classical information theory is the engineering problem of the transmission of information over a noisy channel. The most fundamental results of this theory are Shannon's source coding theorem, which establishes that, on average, the number of bits needed to represent the result of an uncertain event is given by its entropy; and Shannon's noisy-channel coding theorem, which states that reliable communication is possible over noisy channels provided that the rate of communication is below a certain threshold, called the channel capacity. The channel capacity can be approached in practice by using appropriate encoding and decoding system

Chapter 2. Display Systems
2.1 Introduction
Early computers communicated with the user with either indicator lamps or hard copy printers, but today, the primary output device is the electronic display. This is usually the CRT display, although other technologies are available. The enabling display technology for portable computers and the latest personal digital assistants
(PDA) is the liquid crystal display.
2.2 Types of displays
Displays can be classified into following 3 main types in term of technology.
Electronic Displays
CRT Flat Screen
Active Passive
Gas Discharge
(Plasma)
Liquid crystal
(LCD)
Figure 2.2-1 Display technologies.
The CRT display uses the same technology as the television. A vacuum glass tube has at the end of its neck a heated filament. The electrons emitted are attracted towards the face of the screen by the electric field created by the high tension (HT) voltage applied between the cathode and the anode. The beams of electrons pass through the focusing and deflection electrostatic plates or coils along the way. The screen is coated with a thin phosphor layer which emits light when impacted by an electron at that point.
LCDs composed of two plates of glass in close proximity. Each plate has conductive lines evenly spaced, but very close together, on its surface. The two sets of conductive lines on the glass plates are perpendicular to each other so that they form a grid when viewed from the top. On the outside of each glass plate is a polarising filter.
The liquid crystal material is in the centre, between the two sets of conductive lines

6.4 Visual indicators
Visual indicators are widely used for end point detection in the titrimetric analyses. The indicators used normally correspond to the titration reaction and have acid-base or complex-
, precipitate formation or oxidation-reduction properties, respectively. There are, however, titrations in which the indicator reaction type is different from that of the titration reaction.
E.g. some redox indicators can be used for end point detection in complexometric, some precipitate forming indicators in oxidation-reduction, and some acid-base indicators in the precipitation titrations.
6.4.1 Acid-base indicators
Indicators which exhibit a visual change on neutralization by a base or acid at or near the equivalence point of a titration (See Section 6.2.). For characterization and control of purity of acid-base indicators see PAC 57 (6) 845-848 (1985).
6.4.2 Complexometric indicators
The action of indicators in visual complexometric titrations is based on changing a particular optical property (absorption, fluorescence etc.) of the solution titrated in the conditions where the concentration of the free metal aquo ion approaches a defined borderline concentration level. This borderline concentration level should as closely as possible approach the concentration of the free metal aquo ion at the equivalence point of a particular titration reaction. The change of the optical property extends over a range of metal aquo ion concentration which is often defined as the transition range.
The mechanism of the indicator reactions are based on several principles:
i) the indicator forms a coloured complex with the metal ion to be titrated. The uncomplexed indicator may be colourless (one-colour indicators) or coloured in its various protonated form (two-colour indicators). Such indicators are sometimes called metallochromic indicators. ii) When the complexation reaction of interest proceeds in another liquid phase
(usually organic solvent) in equilibrium with the solution being titrated the indicators are described as extraction indicators. iii) When the indicator is influenced by a redox system, whose equilibrium is controlled by removal of the metal ions being titrated, the indicators are called redox indicators, they are usually one-colour indicators.