2024-03-04
Introduction
Summary
keywords
TODO
HW
Exercise*
Next time
Information Representations
Tech in chronological order.
Mechanical
uses gears for moving.
physical representation of state : gears in a specific configuration.
Electrical
our computers.
physical representation of state : voltage or no voltage state.
Optical
optical computing is commercially on the horizon.
It is still too expensive.
physical representation of state : photon present or absent state.
Quantum
completely different tech.
you change the data as you read. -> a finite state does not exist.
Instead, the computations collide into probabilities.
physical repr. are on binary information systems.
data implicit by some physical entity being present or not.
data representations
Computer
binary. 1:4 compression is hexadecimal. 1:3 compression is octal(rarely used)
Human
sexagesimal :12 based system. advantages on exact fractions.
babilonian canaric symbol..
Concept and its representations.
value is different from its representations. The concept is unisome; its presentation can be multiple.
example.number is represented in integer form and real number form( IEEE 754) inside computer.
negative numbers? : 1 bit for direction & other bits for magnitude?
2's complement is a system to express value AND direction integrated at the same time.
character is represented in font(a graphic form), and hard coded to ASCII,EBCDIC,Unicode table. zoned ?
ascii and ebcdic is limited; it uses 8bit (=1byte) for each character repr.
unicode uses 16bit (=2byte) for each character repr.
korean is represented in unicode(2byte) converted into utf-8(3byte) and transmitted.
binary coded decimals are half way between number and character representations. BCD to character, BCD to decimals are easy.
sidenote. zero is technically not a value; it is more of a placeholder.
Zoned formats
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