seven-bit blocks Information & Coding Theory Source Encoding Source/Channel  Decoding Channel/Source Destin- ation Symbols s 1,…,s q Information Channel (errors) Information signal Noise signal + noise Example: Morse Code A, …, Z Encoding transmitter keyer telegraph wire dots, dashes spaces ∙ ─ _ shortwave radio Decoding receiver recognizer A, …, Z Example: ASCII Code Character keyboardmodem terminal screen character Telephone wire seven-bit blocks Symbols s 1,…,s q

Information Source – the symbols are undefined, and the “meaning” of the information being sent is not dealt with – only an abstract measure of the “amount” or “quantity. Examples text of various forms – reports, papers, memos, books, scientific data (numbers) pictures of various forms – diagrams, art, photographic images, scientific data (e.g. from satellites) sound of various forms – music, speech, noises, recorded sound, radio animation of various forms – moving pictures, film, video tape, video camera, television equations representing mathematical ideas or algorithms – two textual representation systems with graphical output: Tex & Mathematica continuous analog waveforms and shapes discrete digital sampled and quantized

Analog vs. Digital Examples of (apparently) analog sources of information: pressure:  + →  granularity – molecular sound (amplitude versus time) intensity: [0, 1]  [0, 1] →  + granularity – crystalline microphone → tape recorder → speaker Examples of (apparently) digital sources of information: Text a′ ? Bsequences of characters different languages have different characters (often the typeface or writing style conveys additional meaning or information) lenses → film (negative) → print (positive) picture (amplitude versus space)

Examples of composites (some digital and analog) color printing (as opposed to photography) television intensity unquantized, temporally discrete color spatially discrete spatially discrete (dots) spectrum discrete (color separation) intensity discrete (dot or no dot) random signal contains largest amount of information