組合語言

.data
chars: .byte 21
num: .word

.text
la $a0, chars
li $a1, 21
li $v0, 8
syscall

la $a0, num
li $v0, 5
syscall

la $t0, chars
la $s0, ($v0)

addi $t1, $zero, 20
addi $s1, $zero, 90
addi $s2, $zero, 32

loop: lb $t7, 0($t0)
if: beq $t7, $s2, L2

beq $t7, 10, L2

beq $t7, 0, L2

add $t7, $t7, $s0

bgt $t7, $s1, L1

sb $t7, 0($t0)
j else

L1: subi $t7, $t7, 26
L2: sb $t7, 0($t0)
j else

else: addi $t0, $t0, 1

subi $t1, $t1, 1

bne $t1, $zero, loop

subi $t0, $t0, 20

li $v0, 4
la $a0, ($t0)
syscall

li $v0, 10
syscall

有獎徵答，知道這篇在做什麼的有獎XD