5.42 · exercise
The price is right
The starter reads a price in cents and a quantity straight into two 32-bit words in .data, price and quantity. Multiply them and store the product in the third word, total. The last lines of the starter load all three words back out of memory and print them, so the bill only shows up if it really is in total.
A value in .data takes two loads to reach: ldr x9, =price puts the address of price in x9, then ldr w10, [x9] fetches the 32-bit value stored at that address. str goes the other way: str w12, [x9] writes w12 to the address in x9.
What is checked
- with input
1299 3the line reads3 x 1299 cents = 3897 cents - the program exits cleanly
mulworks out the bill andstrwrites it to memory- the program also runs on prices and quantities you do not see, including a quantity of 0 and a negative quantity (items handed back)
specification
stdin1299 3
stdoutprints the right output
exitexits with the right code
sourceuses
mulsourceuses
strhiddenright output and exit code on 4 more inputs you do not see
We run your program on the input above and on the hidden ones, and compare what it does. Nothing is matched against a stored solution.