codice:
lw $t0, 0($a0)     # $t0 = primo carattere di $a0
addi $t1,$zero,97  # $t1 = 97
slt $t2,$t0,$t1    # se $t0 >= 97
beq $t2,$zero,upper# vai upper
slt $t4,$t3,$a1    # $t3 < $a1 ??
beq $t4,$zero,esci
li $t3,4
add $t3,$t3,$t3
j uppercase