mirror of
https://github.com/jackyzha0/quartz.git
synced 2025-12-25 13:54:05 -06:00
53 lines
2.1 KiB
Markdown
53 lines
2.1 KiB
Markdown
---
|
||
title: "digital-data"
|
||
aliases:
|
||
tags:
|
||
- cosc204
|
||
---
|
||
|
||
# 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
|
||
|
||
# Bits, Nibbles, Bytes
|
||
- 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)
|
||
|
||
# Memory
|
||
Data is stored in [memory](notes/memory.md)
|
||
|
||
# A Word of 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](https://i.imgur.com/nHrz1zX.png)
|
||
|
||
# Characters
|
||
- A written symbol.
|
||
- In english are represented as a single byte, (other languages use 2 bytes or more)
|
||
- e.g., [different types of characters](https://i.imgur.com/DBLVhw8.png)
|
||
|
||
- 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](notes/unicode.md) or [ASCII](notes/ASCII.md) |