If a line begins with a semicolon (;), it is considered a comment.

Example:

Windows Registry Editor Version 5.00                              ; These are Command Processor Values                              \[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Command Processor\]                              "AutoRun"=""                              "CompletionChar"=dword:00000040                              "DefaultColor"=dword:00000000                              "EnableExtensions"=dword:00000001                              "PathCompletionChar"=dword:00000040