History of the Early Vending Machine and Design Essay
An early vending machine is invented by Hero of Alexandria, a first-century engineer and mathematician . In 1876, Simeon Denham built a vending machine dispensing stamps called “the first fully automatic vending machine”. A modern coin-operated vending machine was first introduced in London in 1883 by Percival Everitt. After that, vending machines have become well-known and been widely used in England.
The following is details about background knowledge related to the design of the vending machine.
2.1 Truth Tables  Figure 2.1: An example of truth table.
Truth tables are a kind of table for describing the set of result for each alternative set of inputs. Using the truth table will help designers to write …show more content…
2.5 Multiplexers/Selectors A multiplexer, or MUX, is a combinational logic network with 2n data inputs, n control inputs, and one data output. 
2.6 Karnaugh Map
Karnaugh Map or K-Map is a useful method for Boolean expression simplification. The goal of using this method is to implement the expression with fewest literals and fewer wires as possible. The concept of Karnaugh map is that when the output does not depend on some inputs, those inputs can be cut off from the expression since its do not affect a result of the output. The Kernaugh map is another way to represent a truth table so the designer can easily grouping