In terms of digital logic, a zero is represented by what??

Question

which of these choices is an exmaple of a product-of-sum (POS) expression??

a) X= A+B+C

b) X= (A+B)(C+D)

c) X=AB+CD

d) X=ABC

Answer 1

1. Low voltage or current

2: b

a. This is a sum

b. This is product of sums

c. This is sum of products

d. This is product

Answer 2

A low voltage, or no voltage condition. Counting in a digital high speed circuit is done by transitions from a "low", zero to a small fraction of a volt, to a "high" which would be close to if not at the most positive voltage of the power supply to the digital circuit. Your Boolean expressions that you give are arbitrary, and do not really express what is happening at any given time, You also do not specify the type of device being used. An inverting counter could be expressed by you choice 'a' and start low, on a high transition remains low, and on the low transition, goes high, because the device could be an inverting device. Boolean Algebra is nice, but you also need to consider the devices that will be used, and how they operate.