what is the meaning of NOP in the schematic diagam?
As Alex said, it is a part property in Sch. Usually, all SCH Tools has a property for each part called "Loading" property. Loading property can be set based on if the part will be loaded or not in the circuit. Their can be multiple reasons to do that. Some are :-
- Uncertain about the part in circuit.
- To give multiple configurable options.
- To be used in diff way in Diff scenarios.
- Multiple Variants of Sch.
Usually it is good to assign a color to this property to highlight such NOP(No Populate), or DNP (Do Not Place) or NM(NoMount) parts.