The Interface Section The interface section of a unit begins with the reserved word interface and continues until the beginning of the
implementation section. The interface section declares constants, types, variables, procedures, and functions that
are available to clients. That is, to other units or programs that wish to use elements from this unit. These entities
are called public because code in other units can access them as if they were declared in the unit itself.
The interface declaration of a procedure or function includes only the routine's signature. That is, the routine's name,
parameters, and return type (for functions). The block containing executable code for the procedure or function
follows in the implementation section. Thus procedure and function declarations in the interface section work like
forward declarations.
The interface declaration for a class must include declarations for all class members: fields, properties, procedures,
and functions.
The interface section can include its own uses clause, which must appear immediately after the keyword interface.
