Comment In Batch, Registry, PowerShell, Bash File

Comment In Microsoft Windows Command Prompt and Batch File

To create a single line comment in batch file start with the REM
REM This is a comment
Other way to create a single line comment in batch file start with double colon ::
:: This is a comment
To create an inline comments in batch file start with the percentage and equal sign %= then end the comment with equal and percentage sign =%
echo "Hello world!" %= This is an inline comment. =%
To create multiline batch comments, start each line with the double colon ::
:: This is the first line :: This is the second line

NOTES:

Batch script file extension is .bat
Inside nested parts (IF/ELSE, FOR loops, etc...) :: should be followed with normal line, otherwise it gives error (use REM there).
if they are not in the beginning of line, then add ampersand & sign character, for example
echo "Hello world!" & :: This is an inline comment.
To avoid printing a REM command to screen, start with @, for example @ REM This is a comment

Comment In Registry File

To create a single line comment in registry file start with the semicolon ;
; This is a comment

NOTES:

Registry file extension is .reg

Comment In PowerShell File

To create a single line comment in registry file start with the start with the hash sign (#):
# This is a comment
To create multiline powershell comments, start each line with the hash sign (#):
# This is the first line # This is the second line
Another way to create multiline block comments is valid in the modern PowerShell version, start with less than and hash mark <# together then end with hash mark and greater than #>
<# 'COMMENT' This is the first line This is the second line #>

NOTES:

PowerShell script file extension ( .ps1 )
PowerShell script data files ( .psd1 ),
PowerShell script module files ( .psm1 ).
and Script Pane are configuration files (.ps1xml), XML based files.

Comment In Linux/Unix Terminal and Bash File

To create a single line comments in bash scripts start with the hash sign (#):
# This is a comment
To create an inline comments in bash scripts start with the hash/number sign (#):
echo "Hello world!" # This is an inline comment.
To create multiline bash comments, start each line with the hash sign (#):
# This is the first line # This is the second line
Another unconventional way to create multiline block comments is to use the bash null command (:) together with the heredoc notation:
: << 'COMMENT' This is the first line This is the second line COMMENT

NOTES:

Linux / Unix command is case sensitive
Bash script file extension is .sh

Bibliography:

https://learn.microsoft.com/ https://phoenixnap.com/ https://ss64.com/ https://stackoverflow.com/ https://www.computerhope.com/, https://www.commandlinefu.com/