The od program can display output in a variety of formats, including octal, hexadecimal, decimal, and ASCII.
It is useful for visualizing data that is not in a human-readable format, like the executable code of a program, or where the primary form is ambiguous (e.g. some Latin, Greek and Cyrillic characters looking similar).
Other loops and logical blocks are opened by the name, and closed by the reversed name, e.g. if ... fi and case ... esac, but od's existence necessitates do ... done.
The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities.
Here is an example of od used to diagnose the output of echo where the user types Ctrl+V+Ctrl+I and Ctrl+V+Ctrl+C after writing "Hello" to literal insert a tab and ^C character: