Assigned: Wed 23 Feb 2000
Due: Wed 1 Mar 2000
This lab consists of a number of exercises involving programming the PC-231 computer
as described in lecture and in the PC-231 Computer Supplement.
Although there is not a lot of documentation on the assembler and simulator programs,
I have demonstrated them in lecture. (The little bit of documentation there is occurs
at the
bottom of the aforementioned supplement.)
Write a short program which will read in a single character of ASCII data and
then print out the both the decimal and hexadecimal equivalents (i.e., the
code for the character in both base 10 and base 16 formats).
If you want to do a bit extra, make your program alternately read and convert
as above, but for any number of ASCII characters, say until a certain character
is read (e.g., an exclamation point).
Your program should be written in assembly language and should follow the
format of the examples given in class and in
the sample programs directory.
If done properly, your output should look like this when you run the
simulator, paste in your program and type "A":
Write a program which will print out the phrase "Hey there!" in ASCII format
(of course,
using the simulator, it will only come out one letter at a time, so it won't
look very pretty). You can use device AD for ASCII output; you'll need to
know the hex values for the letters, but you can either look them up in a chart
or use your program from the previous exercise to compute them.
During demo, I will ask you to modify the program to instead print out your
first name. You can prepare this second version in advance, if you like.
Be prepared to discuss the following:
Write a program which will read in a number in decimal format, then multiply
the number by 16, and finally print out the result. Try to pick a quick and
reasonable way to multiply by 16 (Hint: think binary!).
Now write a program which will read in a number in decimal format, multiply
it by 48, and then print out the result in decimal format again. Note that
48 is not a power of 2, but it's not that far off, either.
Consider the following mystery program:
You should try first to undertand the program by "dis-assembling" it, that is,
by translating it back into a more readable assembly format.
You may also want to run the program through the simulator iin order to better
understand it, but it runs pretty long. You might want to look at the RAM
dump at the end of the program run carefully. In order to look at the actual
instruction execution of the program, you can try modifying it to be shorter
(i.e., run portions of the program separately).
Unfortunately, the way the simulator does input and output is not at the moment
very unix-friendly: piping the program output through a viewing utility such
as "more" doesn't work too well.
Contents
Exercise #1: Converting ASCII charatcers to codes
Starting program execution ...
--------------------------------
Please input a single ASCII character: A
The letter read was hex 041
Decimal output written: 65
Hexadecimal output written: 041
Exercise #2: Printing a simple phrase
Exercise #3: Simple multiplications
Exercise #4: Mystery program
207 307 9EB 30E 9E1 31E 9E2 A31 B32 410 420 408 E0D 000 001 002 003 004 005 006 007
Describe what it does in English. Try to characterize the behavior abstractly,
i.e., explain it in a few words. Don't just say "First it executes this
instruction, then that one, then another one ...". Try to understand what it
is doing at a higher level.