What total amount is given to a waiter if the bill is $25, the tax rate is 8%, and the tip is 15% ? (Use integer math).
total = 25 + (25*(8+15))/100 = 25 + (25*23)/100 = 25 + 575/100 = 30
If the waiter grumbles about getting $30 instead of $31, just explain that in integer math 575/100 = 5.
Write a program that calculates the total cost given the amount for the meal, plus 8% tax, plus 15% tip. The meal amount is input from the user. The tax and tip rates are fixed. Here is a run of the program:
Enter food cost: 25
Tax plus tip: 5
Total cost: 30
Here is a start on the program:
## 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 a prompt (code 4 put in $v0)
la $a0,prompt # address of prompt put in $a0
syscall
li $v0,5 # input an integer (code 5 put in $v0)
syscall # 32-bit result returned in $v0
move $s0,$v0 # save it in $s0
. . . . .
.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 " Total cost: "
The only information needed from the user is the cost of the food.
This is prompted for and then read in (as text) and converted
(by part of the exception handler) into a 32-bit two's complement integer.
The SPIM exception handler expects the service code to be
in register $v0.
Arguments are passed into and returned from
the services in other registers.
See the previous chapter or
Appendix G.
With your mental highlighter, mark the mnemonics
in the code fragment (above) which are pseudoinstructions.