IB Digital Society 1.1B Digital and Analog Systems Notes

1.1B Digital and Analog Systems

Analog vs Digital: Continuous vs Discrete

1. Analog = information as a continuous physical quantity (vinyl groove, mercury thermometer, speedometer needle): any value in range.
2. Digital = information as discrete values: fixed steps with nothing in between. Think of a staircase rather than a smooth ramp.
3. The difference is the gap between steps: an analog dial reads 21.4, 21.43, any value; a digital thermometer jumps 21.4 to 21.5 with nothing shown between.
4. Play a note into both: analog keeps the exact wave shape; digital measures at intervals and stores the nearest allowed value, a staircase copy of the smooth original.

Binary: Everything Becomes 0s and 1s

1. Digital systems store every value in binary, a number system with only two digits, 0 and 1.
2. Each 0 or 1 is a bit, the smallest unit of data, matching a switch's off/on. Two clearly separated states make the hardware dependable.
3. Bits combine fast: 2 bits = 4 patterns, 3 = 8, each extra bit doubles. 8 bits = one byte = 256 patterns, enough for one text character.
4. Because patterns double per bit, the same two digits stand for text, numbers, colours, sound, just longer patterns, no new symbols.

How Text, Images, and Colour Become Bits

1. Rule: agree on a code. Turn each thing into a number, write the number in binary.
2. Text: a character set (ASCII, then Unicode) gives each character a number; capital A = 65 = 01000001.
3. Images: grids of pixels; a common code stores each pixel's colour as red, green, blue (0 to 255), one byte per channel; e.g. 90, 140, 110 = three bytes.
4. Sound: loudness measured as a number many times a second, each stored in binary.