C style comments begin with a slash followed by an asterisk (/*) and end with an asterisk followed by a slash (*/). Also the comment text and the delimiters must be on a single line:

C++ style comments begin with two slashes (//) and end when the end of the line is reached, for example:

// This is a line comment
// Copyright (c) ARM Limited

Comments that begin with //, but are not placed after a command, do not appear in any log and journal files.

Comments can begin with a semicolon (;), for example:

; A comment

Comments can begin with //# and end when the end of the line is reached.

Comments that begin with //#, but are not placed after a command, appear only in a journal file. Also, the //# prefix is replaced with ; in the that file.

Only // or //# comments can be placed at the end of a command, for example:

ADD int value     // integer value

Comments cannot be nested.