# 4.2.1 Sum of Products | Summary and Q&A

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July 12, 2019
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MIT OpenCourseWare
4.2.1 Sum of Products

## TL;DR

Learn techniques for creating combinational logic circuits with truth tables and Boolean equations.

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### Q: What is a functional specification in creating combinational logic circuits?

A functional specification is a part of the static discipline used to create the abstraction of a circuit and can be described using natural language, truth tables, or Boolean equations.

### Q: Why are truth tables practical for circuits with small numbers of inputs?

Truth tables systematically enumerate all combinations of input values, ensuring no combination is omitted. The output values are explicitly specified, leaving little room for misinterpretation.

### Q: How are Boolean equations used to compute output values?

Boolean equations use logical operations (AND, OR, XOR, NOT) to compute output values from input values. The sequence of operations laid out in the equation allows for the computation of output values.

### Q: Can truth tables be converted into Boolean equations?

Yes, truth tables can be converted into a particular form of Boolean equation called a sum-of-products. Each row of the truth table corresponds to a term in the sum-of-products equation.

## Summary & Key Takeaways

• Combinational logic circuits can be created with natural language descriptions, truth tables, or Boolean equations.

• Truth tables are simple and straightforward for circuits with a small number of inputs and outputs.

• Boolean equations are useful for circuits with many inputs and can be easily converted into circuit schematics.