The implementation part of the unit is where you find the bodies of the procedures and functions that are declared in the  interface part of the unit.

The implementation part of the unit is the private part. Declarations made here can be used only within this section of the unit.

All constants, types, variables, procedures, and functions in the interface portion are visible in the implementation.

The implementation can have additional declarations of its own that are not visible to any programs using the unit.

A uses clause can appear in the implementation, immediately following the reserved word implementation.

If any procedures have been declared external, one or more $L filename directive(s) should appear anywhere in the source file before the final end of the unit.

The normal (not inline) procedures and functions declared in the interface must reappear in the implementation.

The procedure/function header in the implementation should be either: