CS 1104 AY T3 Unit 8 Discussion Assignment- University of the People

3/26/2019 CS 1104 - AY2019-T3: Unit 8 Discussion Assignment


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Discussion Forum Unit 8
Unit 8 Discussion Assignment
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Unit 8 Discussion Assignment
by Onyekwere Oluoha (Instructor) - Wednesday, 30 January 2019, 5:40 AM


There are assemblers that are capable of handling macro commands.

Please explain in your own words what a macro command is and provide an example.

When would you program a macro and when would you program a subprogram (also called
functions, subroutines, methods)?


43 words
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Re: Unit 8 Discussion Assignment
by Stanislas Mihaljcuk - Thursday, 21 March 2019, 10:48 AM

Macro commands are shortcut words that execute a speci c sequence of other
predetermined commands. As said in TutorialPoint (n.d.):
https://my.uopeople.edu/mod/forum/discuss.php?d=191807 1/18

,3/26/2019
"A macro is a sequence of instructions, assigned by a name and could be used anywhere
CS 1104 - AY2019-T3: Unit 8 Discussion Assignment

in the program."(TutorialPoint, n.d.)

Here is an example from the textbook:

"If you nd this coding style tedious or even peculiar, you should note that friendlier
macro commands like D=D+M[xxx] and GOTO YYY can easily be introduced into the
language, causing Hack assembly code to be more readable as well as about 50 percent
shorter. The trick is to have the assembler translate these macro commands into binary
code e ecting @xxx followed by D=D+M, @YYY followed by 0;JMP, and so on."(Nisan &
Schocken, p. 117, 2008)

Therefore, instead of doing

@xxx
D=D+M


One could do:

D=D+M[xxx]


this would make the tedious task of getting the memory etc. much easier.

You want to use macros when you are repeating a certain simple task that doesn't
involve logic. When you go fetch a memory block to assign to something, this
information doesn't need its own line, it'd be best if you integrate to the operation itself.
However, if you want some logic, usually a longer combination of code then I'd say a
function is better. This is my opinion.

The main di erence between a macro and function is that the former is pre-processed
while the later is compiled. Macros are faster but are more di cult to debug. Type
checking is done on functions and not on macros. (Macros vs Functions, 2018)




References:

Macros vs Functions. (2018, December 21). Retrieved from
https://www.geeksforgeeks.org/macros-vs-functions/
Nisan, N., & Schocken, S. (2008). The elements of computing systems: Building a modern
computer from rst principles. Cambridge Mass.: The MIT Press.

Tutorialspoint.com. (n.d.). Assembly Macros. Retrieved from
https://www.tutorialspoint.com/assembly_programming/assembly_macros.htm


https://my.uopeople.edu/mod/forum/discuss.php?d=191807 2/18

, 3/26/2019 319 words CS 1104 - AY2019-T3: Unit 8 Discussion Assignment


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Re: Unit 8 Discussion Assignment
by Onyekwere Oluoha (Instructor) - Sunday, 24 March 2019, 6:24 AM


Hello Stanislas/Class,

It was nice reading your post. In addition, function could be described as a named unit
of codes or section of a program, which performs a designated task (Saddleback
College, n.d.). Functions are very helpful in that their use make programs much easier
to read, test and debug. A Macro is very similar to a Function, but each has its unique
purpose based on programmer requirements (Mahipal, Phaneendhar & Srinivas, n.d.).
In addition to your list, the following are major di erences between Macros and
Functions:

1. A Function is assembled once and then can be called from any location.
However, the assembler has to copy and compile the Macro whenever invoked
(Bishop's University, n.d.).

2. Macro have some “side e ect” or downsides as compared to Functions, such as
no type checking for incompatible operand and the likes. These could lead to major
complications if not carefully put into consideration while coding. Also, they are
generally more di cult to debug.

3. Macros avoid overhead of return instructions/calls, register shu ing and
argument passing, which are present in Functions.

4. Macros are processed before program compilation, while functions are
compiled directly.

5. Macros are usually faster than functions in execution speed. This could largely
be attributed to the fact that Macros don’t such overheads (like function calls) as is
present in functions.




OLuOHA.




References

Bishop's University (n.d.) “Macro in assembly language” online. Retrieved from:
http://cs.ubishops.ca/ljensen/asm/marros-assembly.html
https://my.uopeople.edu/mod/forum/discuss.php?d=191807 3/18