CS 2011, A Term 1999
Introduction to Machine Organization and Assembly Language
Extra Credit Project (due Oct. 8)
Instructions
- Write an assembly language procedure named bigmul that accepts
three singleword unsigned integer parameters x, y, n on the stack
and returns a pointer to the product of [x] and [y] in register DI.
Notice that the first two parameters x and y are pointers to the
actual multiplication operands [x] and [y]. The third parameter, n,
indicates the number of words occupied by each of the operands [x]
and [y]; it is assumed that the product [DI] occupies 2n words.
You may restrict the allowable values of n to the interval
1 <= n <= 8 (if you want to be fancier and to allow larger values
of n, use DOS functions for dynamic memory allocation as described
in Irvine, chapter 14). Bigmul should be thought of as having the
prototype bigmul(x,y,n), and C/C++ calling conventions should be
used (however, no linking to C/C++ is required).
- Link bigmul with (an appropriately modified version of) the
main procedure from HW4, which prompts the user for unsigned integer
values of x and y, calls bigmul to compute the product x*y, and
displays the result to the user.
Note that you may need to modify the display procedures so that
larger integer values can be handled. If you plan to modify the
Irvine library procedure Writeint, remember that the source code
presented in the book is incomplete, as it fails to initialize CX and DI.
- Assemble, link, and debug your program using tasm / tlink / td.
Deliverables
- Submit a floppy disk containing the assembly source code for the
bigmul and main procedures as well as any necessary library procedures,
documentation including complete command line assembler/linker options
(follow the
WPI CS documentation standard described at
http://www.cs.wpi.edu/Help/documentation-standard.html),
and a script file showing the DOS window view of a run of your program
as it computes the product 10,000,000,000 times 1,234,567.
(you may use the prn2file utility available on the ccc machines in the
directory /cs/cs2011/ to generate the script file).
- Explain what technical issues you had to address in this assignment
beyond the issues raised by HW4, and describe the main features of your
solutions to these issues.
- Submit hardcopies of the above items.
Everything you submit (files too) must include your name, login, and
section number. Note that no credit will be given for programs that
do not assemble/link correctly under tasm/tlink when the documentation
instructions are followed, or that do not produce correct output in
cases in which the result occupies three or more 16-bit words.
Background Information
Dynamic memory allocation
See Irvine, chapter 14 for information about DOS function calls for
dynamic memory allocation (note that dynamic memory allocation
isn't required for the basic n<=8 version).
