Bits Bytes and Words

Definitions

Bit = Binary digIT = 0 or 1

Byte = a sequence of 8 bits = 00000000, 00000001, ..., or 11111111

Word = a sequence of N bits where N = 16, 32, 64 depending on the computer

There are 2^N words of length N. Why?

How many bytes are there?

Measuring Amount of Data/Memory Capacity

1 kilobyte = 1 KB = 2¹⁰ bytes = 1024 bytes (appx 10³ bytes)

1 Megabyte = 1 MB = 2²⁰ bytes = 1,048,576 bytes (appx 10⁶ bytes)

1 Gigabyte = 1 GB = 2³⁰ bytes = 1,073,741,824 bytes (appx 10⁹ bytes)

What are some other prefixes?

Bandwidth, the speed at which data can be transmitted over a given communication channel, is measured in bits/second.

Representing Bits

A bit can be represented as a voltage in a hardware computer. For example, 3 – 5 volts = 1, 0 – 2 volts = 0.

We can represent Boolean truth values in a virtual computer using bits: 1 = true, 0 = false.