COMT 222 Tools for a Digital World

Digital? What makes information Digital? If it helps:  When is information not analog? Answer:  A finite number of “symbols”  A fixed time associated with a symbol

OK, so what is a symbol? Conveys a digital value Transmitted at a given “symbol rate”, i.e.  A circuit sends a certain number of symbols per second  A symbol takes a fixed amount of time to send In practice a symbol represents a certain number of bits

Binary Is the simplest form of a digital symbol Each binary “symbol” can represent either a 0 or a 1 If a unit of information (often called a symbol) is one bit long, it can send two values

Binary Numbers Converting to and from binary  Position values:

Binary/Decimal Conversion Convert to decimal:  1  11  111  1111  1010 Convert to binary: 27

A related issue Given a number of bits, how many symbols can you make?  1 bit: 0 to 1  2 bits: 00 to 11  3 bits: 000 to 111

Hexadecimal Binary numbers have lots of digits Using another number system allows grouping of bits Hexadecimal digits (and their values):  (What is 15 in binary?) ABCDEF

Bit Groups as Hex Digits A1010 B1011 C1100 D1101 E1110 F1111

Hex to and From Decimal Convert  180 to hex  0x3e to decimal

Application - ASCII Text is digital Need to agree on “encoding” What string of bits do we assign to  COMT 222 ASCII (in hex)  43 4F 4D