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50 lines
1.6 KiB
Markdown
50 lines
1.6 KiB
Markdown
---
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title: "01-bits-and-bytes"
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aliases:
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tags:
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- cosc204
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- lecture
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---
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# What is data
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- A fact — a piece of information
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- corresponds to discreete facts about phenomena from which we gain information abou the world
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- The concept of a *value* is fundamental to data
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- e.g., 25, $356.00, April, "this is a sentence", colours etc
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- Vaues are abstract, they are interpretations of data
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- There are many way of storing the same data
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- e.g., 12, twelve, XII, 1100, · ··, ·----··---
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# How computers represent data
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- In *Binary*
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- Stored in one of two states, true/false, 1/0, on/off, voltage/no voltage
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- Each instance of a state is called a *bit*. (binary digit)
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- *Values* are represented as a sequence of bits.
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- e.g., 1000001
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- The computer doesn't "know" what any given sequence means, **you** know.
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- could be 65, A, or anything **You** want it to mean
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# Computer memory
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- SImilar to the switch board in your home
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- Each switch has a number
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- they are all always there
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- you can switch the state by flipping the switch
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- Each switch has:
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- A address/location (swtich number)
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- A value (on/off)
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- computer languages allow us to name some of the locations, its easuer than remembering its number (variable)
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# Bits, Nibbles, Bytes
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- The smallest unit of storage is a buit (0 or 1)
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- (for convenience) bit are grouped into larger units.
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- a nibble is 4 bits
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- a byte is 8 bits
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- For convenience bytes are given addresses, not nibble or bits. (they are too small to work with most of the time)
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# A Word of memory
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- The word is the number of bits the cpu uses internally, varies between manufacturers and CPUs.
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- Now its usually 64 bits
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