By way of illustration, below is the in-code documentation for Miriad subroutine axistype, which uses the ``directives'' noted previously.
c* Axistype - Find the axis label and plane value in user friendly units c& mchw c: plotting c+ subroutine AxisType(lIn,axis,plane,ctype,label,value,units) c implicit none integer lIn,axis,plane character ctype*9,label*13,units*13 double precision value c c Find the axis label and plane value in user friendly units. c c Inputs: c lIn The handle of the image. c axis The image axis. c plane The image plane along this axis. c Output: c ctype The official ctype for the input axis. c label A nice label for this axis. c value The value at the plane along this axis. c units User friendly units for this axis. c--Note that the programmer has woven executable code into the documentation (the lines that are not commented out): anything between the c+ and the c- is considered to be part of the documentation, even though the lines are actually part of the subroutine code itself.
A subroutine source code file (or a program source code file) may contain multiple subroutines, each documented as above.