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.
5. Meaning is a convention: bits stand for a letter, colour, or sound only because a shared standard says so.

Why Binary Survives Noise

1. Every signal picks up noise: small random distortions from heat, interference, or wear.
2. Analog: noise becomes part of the signal (tape hiss, record crackle) and can't be cleanly separated from the original.
3. Binary only tells 0 from 1, states set far apart: as long as noise doesn't push a value past the halfway point, the digit reads correctly and rebuilds clean. A copy of a copy stays perfect.
4. Extra checks: a parity bit flags a single flipped bit (records whether the count of 1s is odd or even); error correction adds enough bits to detect and repair errors, so data survives scratched discs and long network trips.

Resolution: More Bits, Finer Detail

1. Digital values come in fixed steps, so a digital copy is always an approximation; how close depends on how many steps you allow.
2. More bits per value = smaller steps, so the staircase hugs the curve. At low resolution the blocks show; push it higher and they vanish into a smooth surface.
3. Same idea across all data: more bits per colour = smoother shading, more bits per sound = truer recording. Fidelity = number of allowed values.
4. Cost: more resolution = larger files. Designers weigh fidelity against space.

Compression: Trading Quality for Size

1. High-quality files are large, so almost everything you download or stream is compressed (fewer bits than the raw data). Two kinds.
2. Lossless: no loss; records patterns efficiently and rebuilds the original bit for bit (text, program files, PNG, ZIP).
3. Lossy: throws away detail people won't notice (fine colours, quiet sounds); far smaller, not identical (JPEG, MP3, streamed video).
4. Cost: over-compress a JPEG and blocky artifacts appear. Whoever sets the quality level (platform or user) quietly decides what everyone sees and hears.

Perfect Copies Changed Media

1. The biggest analog/digital difference is copying. An analog copy always loses something (a tape of a tape, a photocopy of a photocopy).
2. A digital copy is identical, bit for bit, and endless copies cost almost nothing, which reshaped how people make, share, and own creative work.
3. Perfect copies make reliable backups and instant access simple. They also make leaks and deepfakes easy. The impact already happened (the move to streaming); the implications (who gets paid, telling real from fake) are still unsettled.

The World Is Analog

1. The physical world is analog (sound, light, temperature, movement vary continuously). Digital systems only represent that world; the world itself stays analog.
2. Two parts bridge the gap: sensors turn a continuous quantity into numbers (mic, camera sensor, thermometer); actuators (outputs) turn numbers back into physical effects (speaker, screen, motor).
3. A digital system is a stretch in the middle of an analog chain: continuous in, bits stored and processed, continuous out.
4. Contested: is digital better than analog? Digital wins on copying and storage; but a continuous signal may capture nuance the discrete steps flatten (vinyl, film). Depends on what you need.