# copy data from first struct to second     
        lw      $t0,0($s1)         # copy age from first
        sw      $t0,0($s2)         # to second struct
        lw      $t0,__4__($s1)     # copy pay from first
        sw      $t0,__4__($s2)     # to second struct
        lw      $t0,__8__($s1)     # copy class from first
        sw      $t0,__8__($s2)     # to second struct

Classic Confusion

Students who rush through this material often pay for their speed with hours of confusion down the line. Working with addresses and the contents of addresses leads to classic confusions. I speak from experience here, both experience with students and experience in being confused.

The classic prevention to classic confusion is to study a simple program. Such as this one. Copy the program into your editor, paste it to a file and play with it.

The program is more interesting if it writes some output. Here is another block of code to insert just before the end:

         
        # write out the second struct    
        ____    $a0,agest         # print "age:"
        ____    $v0,4
        syscall
        ____    $a0,0($s2)        # print age
        ____    $v0,1
        syscall

        ____    $v0,10            # return to OS
        syscall       

        .data
pay:    .word   24000             # rate of pay, in static memory
agest:  .asciiz "age:   "