Reference designators are used in schematics and printed circuit board layouts to label
components. Reference designators are commonly alphanumeric; they consist of a letter indicating
the general category of component followed by a number. Some commonly used reference designator
Reference designators are essential when moving from a schematic to a board layout. You might not
have fixed in your mind what the package size and shape of a given component is, so in order to
recognize it and place it appropriately, you will need to have some means of identifying the component.
Many software packages (such as Mentor Graphics) give the user the option of either assigning
reference designators manually, or letting the software assign them automatically. The automatic
assignment feature is useful for components such as resistors, where there is likely to be a large
quantity of identical parts.