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Basics of Digital Systems - Introduction
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This will be a series of general topics about the concepts of digital systems and programmable logic. A digital system 
is a system made up by logic gates, which transforms logic input into a logic output with a logic function. Memories, processors, cellphones and all kind of electronics have digital circuits, logic gates are the building blocks 
of a digital system. They can be implemented with analog circuits and digital circuits, but with the advance of the semiconductor technology there are much more electronic circuits. These circuits are made up by transistors, MOSFETs, and passive 
components like resistors, capacitors and inductors. 

An ASIC (Application Specific Integrated Circuits) is digital circuit that is on the vast majority of the 
electronic devices. The company does a project of a digital circuit and then fabricates thousands of chips 
to sell in the market. They are smaller, consumes low power, but the initial project costs a lot of money 
and you cannot change the circuit when it is already fabricated. 

An FPGA (Field Programmable Gate Array) is an integrated circuit that can be programmed and reprogrammed 
in the field. It has many logic gates, registers, flip-flops and the user program it configuring the connections between them. The advantage of an FPGA is the versatility that it has for tests and for learning.