General Form:

<any command> $ <any comment>

Examples:

RF2=1K $ Gain should be 100
C1=10p $ Check open-loop gain and phase margin
.param n1=1 //new value

ngspice supports comments that begin with double characters `$ ' (dollar plus space) or `//'. For readability you should precede each comment character with a space. ngspice will accept the single character `$'.

Please note that in .control sections the `;' character means `continuation' and can be used to put more than one statement on a line.