====================================================================
Quiz 11: User Friendly Assembler Program for Computing the Factorial	[TOC]
====================================================================

Write an assembly program `factorial.s` where a user is first asked to type in
some unsigned integer $n$, then prints the value of $n$ followed by the string
"`! = `" (characters: '`!`', space, '`=`', space) and then prints the value of
$n!$ followed by a newline. So an example run could look as follows:

---- CODE (type=txt) ----
theon$ 1_ulm_build/func/ulm a.out
n = 0
0! = 1
theon$ 1_ulm_build/func/ulm a.out
n = 1
1! = 1
theon$ 1_ulm_build/func/ulm a.out
n = 2
2! = 2
theon$ 1_ulm_build/func/ulm a.out
n = 3
3! = 6
theon$ 1_ulm_build/func/ulm a.out
n = 4
4! = 24
theon$ 1_ulm_build/func/ulm a.out
n = 5
5! = 120
theon$ 1_ulm_build/func/ulm a.out
n = 6
6! = 720
theon$ 1_ulm_build/func/ulm a.out
n = 7
7! = 5040
theon$ 1_ulm_build/func/ulm a.out
n = 15
15! = 1307674368000
-------------------------

Submit your program and the used `isa.txt` with `submit hpc quiz11 isa.txt
factorial.s`

How Submit Checks Results
=========================

---- SHELL (path=session12/func/, hide) ----------------------------------------
make
1_ulm_build/func/ulmas factorial.s
--------------------------------------------------------------------------------


Submit will use shell command to get results computed by your program. It
therefore uses the `echo` connected by a pipe with your program. Try this with
your program yourself:

---- SHELL (path=session12/func/) ----------------------------------------------
echo 5 | 1_ulm_build/func/ulm a.out
--------------------------------------------------------------------------------

So the output that you see does not contain the user input. It only contains
what your program prints, i.e.

- the string "`n = `" (without a newline),
- the value of $n$,
- the string "`! = `" (without a newline),
- the value of $n!$,

In addition it will write the output of your program into a file, like this:

---- SHELL (path=session12/func/) ----------------------------------------------
echo 5 | 1_ulm_build/func/ulm a.out > res
--------------------------------------------------------------------------------

It will then compare with `diff` whether `res` contains what we expect by
comparing it with some solution file `sol`.

So obviously file `res` here contains

:import: session12/func/res
---- SHELL (path=session12/func/, hide) ----------------------------------------
cp res sol
--------------------------------------------------------------------------------

and this is identical with the content of `sol`. But let's assume `res` would
have this content (where a space is missing now):

---- CODE (file=session12/func/res_ups) ----------------------------------------
n = 5! =120
--------------------------------------------------------------------------------

Then with `diff` we get

---- SHELL (path=session12/func/) ----------------------------------------------
diff res_ups sol
--------------------------------------------------------------------------------

and this will also show up in the error report.