Hexeditor

Purpose

The purpose of a hex editor is to be able to view a page in hexadecimal instead of standard ASCII. This is the main way to be able to create a binary without needing to type extended ascii, or program at all. Hex editors are also used to convert decimal to hexadecimal vice versa.

Counting in hexadecimal is different from counting in decimal.

Decimal: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Hexadecimal: 1 2 3 4 5 6 7 8 9 A B C D E F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F

Some Hex Editors

HexEdit - hex editor for Windows
HxD - freeware hex editor by Maël Hörz.
Hex Fiend - open source hex editor for MacOS