Introduction

Let's learn about the lowest level of computing, and that is Digital Circuits. And let's start by understanding few key concepts.

What is Signal?

Signal is a function that represents the variation of a physical quantity with respect to a parameter.
In Electronics, Signal is a variation of Electrical quantity with respect to time.

What is Analog Signal?

Signals that represent information in a continuous range are called Analog Signals. e.g. Temperature at a given point of time.

What is Digital Signal?

Signals that represent information in a sequence of discrete values are called Digital Signals. e.g. Temperature at a given point of time is hot or cold.

What is Discrete Time Signal?

Signals that represent information in discrete time intervals is called Discrete Time Signal. e.g. Temperature everyday at 9 am in the morning.

What is Noise?

Noise is an unwanted Signal. e.g. what irritates us in phone calls, or video calls.

What is a Digital System?

A Digital System is a system that processes Digital Signals to perform various kinds of Operations. e.g. Computer, Calculator, etc. are Digital Systems. Digital Systems follow below hierarchy.
Digital System -> Sub-systems -> Modules -> Units (Logic Gates) -> Circuits (Transistors)

Advantages of Digital Signals Over Analog Signals

All real-life signals are analog signals. We have to convert them to Digital signals. It costs money, but is worth it! Let's understand how.

1. Digital Signals can cancel out smaller amounts of noise and give accurate information because it represents data in a sequence of discrete values.
2. Digital Signals can be processed and used easily by us. Analog Signals are complex and sometimes too difficult to use.
3. Digital Signals are a sequence of discrete values and hence can be easily reproduced when required. To give a more Philosophical example you can replay a video game, try out as well as copy different strategies, but it's not possible doing the same in the game of life.
4. There are more advantages also, like the use of less bandwidth, encryption, etc.

What is a Switch?

Switch is a Device that can connect and disconnect an Electrical circuit.
We can create layers of discrete values using switches. For example with only 1 switch we have either on or off, 1 or 0, 2 values. But with 2 switches we have 11, 10, 01, 00, 4 values. With 3 swiches we have 111, 110, 101, 100, 011, 010, 001, 000, 8 values. For n switches we have 2 ** n values.
Hence switch becomes an integral part of Digital Electronics.

Conclusion

These are some of the basic terminologies we should be familiar with and going forward we'll delve deep into Digital Electronics. Cheers!