How do you add programme comments?

It depends on the language.

In most cases a remark or comment is denoted by a token or symbol such that the remainder of that line is ignored by the language compiler or interpreter. That is, the comment extends to the end of the line it appears on (known as a single-line comment). However, some languages require that comments be placed on a separate line, by themselves, including BASIC which traditionally opens a comment with the keyWord REM (short for remark).

In C, comments are enclosed in paired delimiters, beginning with /* and ending with */. This convention allows comments to extend across multiple lines as well as to insert comments inside code statements. Languages derived from C, including C++ and C#, also use this convention (known as a C-style comment), but they also allow single-line comments beginning with a // (double-slash) token. Java uses the same syntax as C++ and therefore uses the same comment style. Some languages use the # (pound) symbol to begin a comment while Visual Basic uses a ' (apostrophe).

Java

Additional information on comments can be found in your language documentation.