Much of the research literature available to the network designer may often appear impenetrable; since the language used to express ideas involves advanced mathematical notation. Although this book is not heavily numerical, it is assumed that the reader has a basic grasp of mathematics, as the use of mathematical conventions in some areas of network design is unavoidable. In this appendix we will briefly review a selection of the more common techniques applicable to data communications design theory.

B.1 Operators

• +	Add		Multiply
  -	Subtract		Divide
  =	Equals	?	Note equal to
  ?	or ? Approximately equal to	<	Less than
  >	Greater than	?	Less than or equal to
  ?	Greater or equal to	?	Raised to the power of
  ?	The square root of	?	Tends to or approaches

B.2 Numbers

Real numbers are numbers that can take a positive, negative, or zero value. For example:

• -400, -20, -11.75, -3, 0, +1, +3.76, +1000

Integers are whole numbers, positive or negative, that have no fractional parts. For example:

• -400, -20, -11, -3, 0, +1, +3, +1000

Rational Numbers are fractional numbers and may be positive or negative. Rational numbers include fractions that are less than one, those that are greater than one (so-called improper fractions). Formally stated rational numbers have the form a/b, where a and b are integers, b cannot be zero, and there are no common factors (i.e., 4/6 should be reduced to 2/3). Note that b