he memory unit of a computer has 2 20 words. The computer has instruction format with four fields; an operation code field, a mode field to specify one of 4 addressing modes, a register address field to specify one of 6 5 processor registers, and a memory address.

Assume an instruction is 32 bits long. Answer the following:
A: How large must the mode field be? B: How large must the register field be? C: How large must the address field be? D: How large is the opcode field?