.data
string: .space 100
.text
main:
la $a0,string
li $a1,100
li $v0,8
syscall
jal trans
li $v0,4
syscall
li $v0,10
syscall

trans:
move $a2,$a0
li   $t0,0x61#t0='a'
li   $t1,0x7a#t1='z'
li   $t3,0#counter

again:
lb   $t2,($a2)#注意与lw区别
beqz $t2,ret
blt  $t2,$t0,next#t2<'a'
bgt  $t2,$t1,next#t2>'z'
addi $t2,$t2,-0x20
sb   $t2,($a2)

next:
addi $a2,$a2,1
addi $t3,$t3,1
blt  $t3,$a1,again
ret:
jr   $ra