Binary Numbers

All data inside the computer is represented by means of binary numbers. A binary (base 2) number has only two digit values: 0 and 1. A bit, an abbreviation of binary digit, can be either 0 or 1; a bit is the basic unit of memory. We can use a sequence of bits to represent a number. A binary number such as 111001 represents:

	1	2^5 =	32
+	1	2^4 =	16
+	1	2^3 =	8
+	0	2^2 =	0
+	0	2^1 =	0
+	1	2^0 =	1
		=	57

We can also use a bit to represent false ( 0) or true ( 1). Several Boolean functions are defined:

• and(x,y) is 1 if x = 1 and y = 1, otherwise 0.

• or(x,y) is 1 if x = 1 or y = 1, otherwise 0.

• not(x) is 1 if x = 0, otherwise 0.

A byte is a sequence of 8 bits; it can be used to represent a character by assigning a character code to each character.

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