| Midterm on Monday: Chapters 1-5,7,8 |
| Everyone knows computers use bits and bytes … but what are they? |
| Digitization: representing information by any fixed set of symbols |
| Usually there are not enough symbols | ||
| The solution is to create more symbols by composing patterns … | ||
| Three patterns alone could be symbols, but grouping them together makes 9 when they are pairs, 27 as triples, and ... | ||
| Encode the Latin alphabet |
| Physical world: | |||
| The most fundamental representation of information is presence/absence of a phenomenon | |||
| matter, light, magnetism, flow, charge, … | |||
| detect: “Is the phenomenon present?” | |||
| set: make phenomenon present or absent | |||
| Logical World: | |||
| Information, reasoning, computation are formulated by true/false and logic | |||
| All men are mortal | |||
| Aristotle is a man | |||
| Aristotle is mortal | |||
| True and false can be the patterns for encoding information | |||
| The miracle of IT is that physical and logical worlds can be connected |
| PandA is a binary representation because it uses 2 patterns | ||
| Bit -- it’s a contraction for “binary digit” | ||
| -- a position in space/time capable of being set and detected in 2 patterns | ||
| A byte is eight bits treated as a unit | ||
| Adopted by IBM in 1960s | ||
| A standard measure ever since | ||
| Bytes encode the Latin alphabet using ASCII -- the American Standard Code for Information Interchange | ||
| I need 8 volunteers, 4 women & 4 men |
| Bits and bytes encode the information, but that’s not all | ||
| Tags encode format and some structure in word processors | ||
| Tags encode format and some structure in HTML | ||
| In the Oxford English Dictionary tags encode structure and some formatting | ||
| IT joins physical & logical domains so physical devices do our logical work | ||
| Symbols represent things 1-to-1 | ||
| Create symbols by grouping patterns | ||
| PandA representation is fundamental | ||
| Bit, a place where 2 patterns set/detect | ||
| ASCII is a byte encoding of Latin abet | ||
| In addition to content, encode structure | ||