What is data

A fact — a piece of information
- corresponds to discreete facts about phenomena from which we gain information abou the world
The concept of a value is fundamental to data
- e.g., 25, $356.00, April, "this is a sentence", colours etc
Vaues are abstract, they are interpretations of data
- There are many way of storing the same data
- e.g., 12, twelve, XII, 1100, · ··, ·----··---

How computers represent data

In Binary
Stored in one of two states, true/false, 1/0, on/off, voltage/no voltage
Each instance of a state is called a bit. (binary digit)
Values are represented as a sequence of bits.
- e.g., 1000001
- The computer doesn't "know" what any given sequence means, you know.
- could be 65, A, or anything You want it to mean

The smallest unit of storage is a buit (0 or 1)
(for convenience) bit are grouped into larger units.
- a nibble is 4 bits
- a byte is 8 bits
For convenience bytes are given addresses, not nibbles or bits. (they are too small to work with most of the time)

Data is stored in memory

The word is the number of bits the cpu uses internally, varies between manufacturers and CPUs.
Now its usually 64 bits
amount of bits for different devices

A written symbol.
In english are represented as a single byte, (other languages use 2 bytes or more)
e.g., different types of characters
characters are joined together to make human readable numbers and words
char ch
ch is a variable name (identifier)
used to label a location in the computer's memory where a byte is stored
when the code is compile, the name is assigned an address, in memory. The meaning of that data depends on how a human interprets it. it might be small integer, or a character, or a color etc.d
each byte (or group of bytes) represents a number which maps to a character using a mapping like unicode or ASCII