Bits and Bytes

At the smallest scale in the computer, information is stored as bits and bytes. In this section, we'll look at how that works.

Bit

• Bit -- like an atom -- the smallest unit of storage
• A bit stores just a 0 or 1
• "Computer is all 0's and 1's" ... bits
• Anything with two separate states can store 1 bit
  --Nick's tennis racket example
• Chip uses electricity 0/1 states
• Hard drive uses spots North/South magnetism 0/1 states
• Bit too small to be much use
• Group 8 bits into a byte

Everything in a computer is 0's and 1's ... what does that mean? The bit stores just a 0 or 1 .. it's the smallest building block of storage.

Byte

• One byte = grouping of 8 bits
• e.g. 0 1 0 1 1 0 1 0
• One byte can store one letter, e.g. 'b' or 'x'

How much exactly can one byte hold?

• How many distinct/separate patterns can be made with 1, 2, or 3 bits?
• (Not hold you responsible for details, go through derivation)

• 3 Bits
• Consider just the leftmost bit
• It can only be 0 or 1
• Lefmost bit is 0, append 2-bit patterns
• Leftmost bit is 1, append 2-bit patterns again
• Result ... 3-bits has twice as many patterns as 2-bits

• In general: add 1 bit, double the number of patterns
• 1 bit - 2 patterns
• 2 bits - 4
• 3 bits - 8
• 4 bits - 16
• 5 bits - 32
• 6 bits - 64
• 7 bits - 128
• 8 bits - 256
• Mathematically: n bits yields 2ⁿ patterns (2 to the nth power)

One Byte - 256 Patterns

• Need to know:
• 1 byte is group of 8 bits
• 8 bits can make 256 different patterns
• How to use the 256 patterns?
• How to store a number in a byte?
• Start with 0, go up, one pattern per number, until run out of patterns (256)
• 0, 1, 2, 3, 4, 5, ... 254, 255
• One byte holds a number 0..255
• Code: pixel.setRed(n) took a number 0..255. Why?
• Red value stored in one byte