Why is there no auxiliary operation code for MIPS?

Question

I am very new to assembly language . I read about the MIPS architecture and found out that you have addi code but no subi . Can someone explain to me why we don't have subi ?

Thanks in advance.

Answer 1

When you create a set of commands, you are bound by some restrictions, such as the total number of instructions that you can create. The creators of MIPS realized that there was no need for subi (because you can add a negative number using addi using 2 additions), and they just decided to abandon this instruction. Perhaps this was to save the number of instructions, or simply because it was not needed.

Answer 2

Both addi and addiu accept 16-bit signed operators as an operand, so it makes no sense to add separate subi and subiu .