END DIRECTIVE: ENDS directive ends a segment and ENDP directive ends a procedure and END directive ends whole program which appears as last statement.

ASSUME Directive:  An .EXE program uses SS register to address base of stack, DS to address base of data segment, CS to address base of code segment and ES register to address base of Extra segment. This directive tells assembler to associate segment register with a segment name. For illustration, 

ASSUME SS: stack_seg_name, DS: data_seg_name, CS: code_seg_name.