The symbols used thus far in the chapter for representing different types of gate are the ones that are better known to all of us and have been in use for many years. Each logic gate has a symbol with a distinct shape.
However, for more complex logic devices, e.g. sequential logic devices like flip-flops, counters, registers or arithmetic circuits, such as adders, subtractors, etc., these symbols do not carry any useful information. A new set of standard symbols was introduced in 1984 under IEEE/ANSI Standard 91–1984.
The logic symbols given under this standard are being increasingly used now and have even started appearing in the literature published by manufacturers of digital integrated circuits. The utility of this new standard will be more evident in the following paragraphs as we go through its salient features and illustrate them with practical examples.
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