quartz/content/notes/01-bits-and-bytes.md

title	aliases	tags
01-bits-and-bytes		cosc204 lecture

What is data

• A fact — a piece of information
  • corresponds to discreete facts about phenomena from which we gain information abou the world
• The concept of a value is fundamental to data
  • e.g., 25, $356.00, April, "this is a sentence", colours etc
• Vaues are abstract, they are interpretations of data
  • There are many way of storing the same data
  • e.g., 12, twelve, XII, 1100, · ··, ·----··---

How computers represent data

• In Binary
• Stored in one of two states, true/false, 1/0, on/off, voltage/no voltage
• Each instance of a state is called a bit. (binary digit)
• Values are represented as a sequence of bits.
  • e.g., 1000001
  • The computer doesn't "know" what any given sequence means, you know.
  • could be 65, A, or anything You want it to mean

Computer memory

• SImilar to the switch board in your home

• Each switch has a number

• they are all always there

• you can switch the state by flipping the switch

• Each switch has:

  • A address/location (swtich number)
  • A value (on/off)

• computer languages allow us to name some of the locations, its easuer than remembering its number (variable)

Bits, Nibbles, Bytes

• The smallest unit of storage is a buit (0 or 1)
• (for convenience) bit are grouped into larger units.
  • a nibble is 4 bits
  • a byte is 8 bits
• For convenience bytes are given addresses, not nibble or bits. (they are too small to work with most of the time)

A Word of memory

• The word is the number of bits the cpu uses internally, varies between manufacturers and CPUs.
• Now its usually 64 bits