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How can we implement a conditional statement using basic logic gates? To answer this question, I will 
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introduce you to the multiplexer concept as the building block of the decision making process in hardware.
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A multiplexer is one of the basic concepts in logic circuits. 
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It is a digital switch in which the output o is either a or b, depending on the value of s.
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If s is 0 then o is the same as a. And if s is 1 then o is the same as b. The multiplexer 
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has two types of inputs: Data inputs which determine the different options of the output,
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Select or control inputs which choose one of the inputs to be connected to the output.
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A generalised multiplexer can have n data inputs, m select inputs and one output. A value on the 
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select input connects one of the data inputs to the output. In order to have a practical circuit, 
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the number of data inputs should be less or equal than 2 to the mth power.
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A multiplexer can be implemented by basic logic gates. This design is a typical implementation 
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of a 2x1 multiplexer using AND, OR and NOT gates.
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When the s is 0 then a propagates to the output
And when s is 1 b propagates to the output.
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After getting familiar with the concept of the multiplexer. The question is: What is the generalised 
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form of a multiplexer in a real design? In the next lecture, 
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I will answer this question. 
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These are the takeaway messages. Multiplexer is the primary building block in implementing a decision-making 
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process in hardware.
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A multiplexer has two groups of inputs, including data and select, and an output.
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Now the quiz question. How can a group of basic logic gates implement this 4x1 multiplexer?