# 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 = 2^{10} bytes = 1024 bytes (appx 10^{3}
bytes)

1 Megabyte = 1 MB = 2^{20} bytes = 1,048,576 bytes (appx
10^{6} bytes)

1 Gigabyte = 1 GB = 2^{30} bytes = 1,073,741,824 bytes
(appx 10^{9} 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.