About load and store in mips

Question

First I want to make sure do you use load when it’s the address or the value that is stored in register ?

and I know the are different types of load instructions like lw, lh,lb etc. how can I know when to use which ?

and when is it that I would need to use sw?

Answer 1

Hello, Yasmeen,

On the MIPS architecture, a load instruction (lw, lh, lb) is the only way to bring data from memory to a register. A store instruction (sw, sh, sb) moves data in the other direction, from register to memory. All other instructions read and or write data contained in registers. The reason that there are 3 load and 3 store instructions is because of the support for moving data between registers and memory of different widths (sizes). lw and sw move 'word' data, 32 bits wide, which is the 'natural' width of data on this architecture. lh and sh move 'half word' data, 16 bits wide; while lb and sb move 'byte' data, 8 bits wide.

The data in a register is always a word, and therefore 32 bits wide. This data could be an address, a signed integer, or an unsigned integer. If your code is using only the low order 16 bits, you can consider the data to be a half-word (or if 8 bits, a byte, respectively).

I hope this answers your questions. If not, please let me know!

-+- Sid