Digital Electronics

As said (optional Previous section), for devices like mobile phone,calculators etc,when inputs are ready, decision needs to be taken on those inputs.
But how do you take decisions ? The inputs can be of two types: Quantity and logic.

•  Quantity: It is mere value of the input, say 1010 is input. Its value is 10(decimal). This can be 10 Kg (for digital weighing machine) or 10 min for digital watch etc.  Hence we need to know about Number Representations. Hence the sub-topic which can be understood in details from other web sources. Some of them will be listed here.

• Logic:  Something is 'TRUE' or 'FALSE' and take basic decisions on inputs like this 'OR' that , this 'AND' that. For example, to switch on a mobile phone, we need to press and hold power button for say 3 secs. So the electronics system need to decide to switch on the phone when : "Power button pressed" 'AND' "Pressed for 3secs". Hence 'AND' is a logical operator. The user key press input on the mobile phone for "Power button pressed" can be either 'TRUE' or 'FALSE'. Similarly input time of the power button key press("Pressed for 3secs") can be 'TRUE' or 'FALSE'. The logic operator 'AND'  will result in the condition to switch on the phone only when both are TRUE.

This leads to the need for logical operators like 'AND','OR','NOT' etc. These logic operators are implemented in physical(called logic gates) using sub electronic devices like transistors and diodes. These electronic devices nowadays are dealt under Solid State Electronics).