Question

Op-code Operand   Description 1    RXY       LOAD register R from cell XY 2    RXY       LOAD register R with value XY 3    RXY       STORE register R in cell XY 4    0RS       MOVE R to S 5    RST       ADD S and T into R (2’s comp.) 6    RST       ADD S and T into R (floating pt.) 7    RST       OR S and T into R 8    RST       AND S and T into R 9    RST       XOR S and T into R A    R0X       ROTATE register R X times B    RXY       JUMP to address XY if register R equals 0 C    000       HALT     R, S, T -- Registers 0 - F

Given the above machine language, explain what the following machine code instruction would do:

8123

Answer 1

Here we can see that each instruction contains for hexadecimal digits where the first leftmost digit is opcode and then remaining digits will be as per the operand of the instruction.

Now in machine code 8123, the leftmost digit is 8 which is opcode of Load instruction such that " 8 RST" indicate AND register S and T into R. Similarly here in machine code 8123, here R=1 and S=2, T = 3, hence the instruction with opcode 8123 will "perform AND operation of content of register 2 and register 3 and store the result into register 1".

Please comment for any clarification.