Question

We wish to execute a single LC-3 instruction that will subtract the decimal number 25 from register 1 and put the result in register 2. Can we do it, if yes, show how it would be done, if not, explain why not

Answer 1

Answer:

No

Explanation:

Brief introduction to lc-3

The LC-3 defines a word size of 16 bits for its registers. It also utilizes a 16 bit addressable memory with 216 location address space. The register file has 8 registers( R0 - R7), and  all its registers are referred to as general-purpose registers because they can  be freely used by any of the instructions that is enabled to write to the register file.

No,  it is not possible to use a single LC-3 instruction to implement the subtraction operation, because we only have a 5-bit 2’s complement immediate value which can only be used to represent values between -16 and 15