lw, lh, and lb Instructions

The operands for all arithmetic and logic operations are contained in registers. To operate on data in main memory, the data is first copied into registers. The following gives three load instructions:
lw rd, mem         # load word
The lw instruction loads a word into a register from memory. When a word (4-bytes) is loaded or stored the memory address must be a multiple of four. This is called an alignment restriction. Addresses that are a multiple of four are called word aligned. This restriction makes the hardware simpler and faster.

lh rd, mem         # load halfword
The alignment restriction is also applied to lh, where the address must be halfword aligned. Attempting to load a halfword from an unaligned address will cause a trap. It extends the sign bit of the halfword in memory into the upper two bytes of the register. lhu extends with zeros.

lb rd, mem         # load byte
The lb instruction loads the byte from memory into the low order eight bits of the register. Another way to say this is that the lb instruction loads the register with a 32-bit sign extended version of the byte at the designated address. lbu extends with zeros.
lw lh lw 
      .data
 val  .word   -10

      .text
      lw  $a0, val
      li  $v0, 1
      syscall
 
       .data
 val:  .half   -10

       .text 
       lh  $a0, val
       li  $v0, 1
       syscall
 
       .data
 val:  .byte   -10 

       .text 
       lw  $a0, val
       li  $v0, 1
       syscall
Output Output Output









lb     
       .data
 val:  .byte   -10

       .text
       lb  $a0, val
       li  $v0, 1
       syscall
 		   
Output    













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