See below.
The program is complete and can be copied into your program editor for running and play. Remember in the SPIM settings to allow pseudoinstructions and to load the trap handler file.
## rest.asm
##
## Total restaurant bill calculator
##
## Register Use:
##
## $s0 meal cost
## $s1 tip rate
## $s2 tax rate
## $s3 total rate
## $s4 tax+tip dollars
## $s5 total bill
.globl main
# Get meal cost
main: li $v0,4 # print prompt
la $a0,prompt
syscall
li $v0,5 # input meal cost
syscall
move $s0,$v0 # save it in $s0
# Calculations
lw $s1,tip # get tip rate
lw $s2,tax # get tax rate
nop
addu $s3,$s1,$s2 # (tax + tip) in percent
mul $s4,$s0,$s3 # mealcost*(total rate)
div $s4,$s4,100 # mealcost*(total rate)/100
addu $s5,$s0,$s4 # total bill
# Output
li $v0,4 # print string
la $a0,head1 # "tax plus tip"
syscall
move $a0,$s4 # get tax+tip
li $v0,1 # print integer
syscall #
li $v0,4 # print string
la $a0,head2 # "total cost"
syscall
move $a0,$s5 # get total
li $v0,1 # print integer
syscall #
li $v0,10 # exit
syscall
.data
tip: .word 15 # tip rate in percent
tax: .word 8 # tax rate in percent
prompt: .asciiz "Enter food cost: "
head1 : .asciiz " Tax plus tip: "
head2 : .asciiz "\n Total cost: "
The program has three sections. The sections are reflected in the documentation.
#data input #calculation #output
This is a common design pattern. Keep the phases of a computation together.
This design scheme fits many situations. In a big program, the three stages might each be implemented as a subroutine.
Each subroutine could be designed and tested separately.
What is the bit pattern in register $t1 after the following:
li $t0,0x12345678 sll $t1,$t0,8