Only instructions with zero, one, and two addresses are supported by some CPUs. The size of an op-code is 16 bits, whereas the size of an address is 4 bits.What is the Maximum number of two address instructions?Correct answer is '256'. Can you explain this answer?

Question

Answer

The Maximum Number of Two-Address Instructions

In order to determine the maximum number of two-address instructions, we need to consider the size of the op-code and the size of the address.

Size of Op-code
The size of the op-code is given as 16 bits. This means that the op-code can have 2^16 = 65536 different values.

Size of Address
The size of the address is given as 4 bits. This means that the address can have 2^4 = 16 different values.

Two-Address Instructions
A two-address instruction is an instruction that operates on two operands and requires two addresses. In this case, the instruction format would typically include two fields for the addresses of the operands.

Calculating the Maximum Number of Two-Address Instructions
To calculate the maximum number of two-address instructions, we need to consider the number of possible combinations of op-code and address fields.

Number of Possible Op-code Values
As mentioned earlier, the op-code can have 65536 different values.

Number of Possible Address Combinations
Since the address field has 4 bits, it can have 16 different values. For each operand, we have 16 possible values, giving us a total of 16 * 16 = 256 possible combinations of addresses.

Total Number of Two-Address Instructions
To calculate the total number of two-address instructions, we multiply the number of possible op-code values by the number of possible address combinations.

Total Number of Two-Address Instructions = Number of Op-code Values * Number of Address Combinations
= 65536 * 256
= 16777216

Conclusion
The maximum number of two-address instructions is 16777216. However, since the size of the op-code is 16 bits and the size of the address is 4 bits, only instructions with zero, one, and two addresses are supported by some CPUs. Therefore, the maximum number of two-address instructions is limited to the number of possible address combinations, which is 256.

Answer

Two Address Instructions:

Commercial computers frequently have this. Two addresses can be supplied in the instruction in this case. Instead of the result being saved in the accumulator as it was in prior address instructions, the result can now be stored in many locations, however, this requires extra bits to indicate the address.

Explanation:

The given data,
The CPU supports op-code size = 16 bits
Address size = 4 bits

We have two operands so it requires the 2 x 4 bits =8
And remaining 16-8 bits can be used for two address instructions.
i.e 8 bits.
Maximum number of instructions = 2⁸ = 256
Hence the correct answer is 256.

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