In addition, there are three registers and two 1-bit flags accessible only to the control
unit.The registers are as follows:
E serves as both a memory address register (MAR) and temporary storage
F program counter
G another temporary register; used for counting
Table 16.1 lists the machine instruction set for this example. Table 16.2 is the
complete set of microinstructions, expressed in symbolic form, that implements
the control unit. Thus, a total of 38 microinstructions is all that is required to define
the system completely.