1. Paradigm and the basic building block

In order to present our paradigm in learning electronics, we can take an example of a full adder chip that enables binary addition. Let us use a top-down approach, and look at the datasheet of the TTL (Transistor-Transistor Logic) chip 7483 (http://www.ece.sunysb.edu/~dima/74ls83a.pdf). In the datasheet, we can find out that the chip performs the addition of two 4-bit binary words, A and B, and the pin organization of the chip is the following:

Figure 1-1 Chip 7483

If we continue our investigation to the lower level (Wikipedia, for example), we will find out that a 1-bit adder is built of XOR, AND and OR gates. Do not worry if all this symbols and logic are not familiar. Soon you will master them with ease.

Figure 1-2 1-bit full adder
(Source: referenced)

Finally, on the very bottom level, all the gates can be built using transistors, as shown for the AND gate in the following figure.

Figure 1-3 Transistor AND gate
(Source: referenced)

If we reverse the order and approach the idea bottom-up, it becomes inevitable to understand the working principle of the transistor in order to build gates, from which we can finally build a full adder. Guided by this thought, we are essentially presenting our paradigm in learning electronics – each component that we are going to use, we must fully explain and understand to earn justification to use it as a building block.
The basic building block, therefore, is a transistor, and the first step in understanding its inner workings is inevitably the diode.

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References:

https://commons.wikimedia.org/wiki/File:Full-adder.svg

https://commons.wikimedia.org/wiki/File:TransistorANDgate.png

http://www.ece.sunysb.edu/~dima/74ls83a.pdf