(computers) Need help w/ Homework - Sitcoms Online Message Boards

Warm & Fuzzy · 01-22-2006, 02:51 PM

Can someone help me with this problem, please?

It's computer architecture, and I've been stuck with it for the longest of time. Thanks in advance!

robyrob · 01-22-2006, 06:42 PM

its been a long time since i messed with any boolean logic expressions but I'll try to help; i wasn't familiar with the notation that uses the bar over the top of each letter to indicate a negative or false expression, but if you convert it to a conventional expression (using ~ to indicate negation):

~(~a + ~b + ~cd~e) + ~(~bc~d)

NOT(NOTa AND NOTb AND NOTc AND d AND NOTe) AND NOT(NOTb AND c AND NOTd)

you may want to draw a map or truth tables first

http://dept-info.labri.u-bordeaux.fr...ial/gates.html
http://cnx.rice.edu/content/m13240/latest/
http://www.gamezero.com/team-0/artic...o/boolean.html

i dont remember enough to tell if you can reduce it further, (for example ~(~a AND ~b) = a OR b ) but I really dont know what your teacher is looking for...

Warm & Fuzzy · 01-22-2006, 06:51 PM

AHHH!! My savior! *bows down to thee* LOL.
Let's see... this is what I have written down... is it in "simplest form," though?
Like, is this the least number of gates that I can use? Or can I use even LESS? (I can only use AND, OR, and INVERTER). I used 14, I believe.

And I prefer to use the bar to indicate an inverse because it takes up less space when writing, LOL. The '~' symbol takes up the space of a character, and I am limited to an 8x11" paper, hehe.

Oh, and I also need assistance in one more question, LOL.

Design:
Use truth tables, SOP expression, simplify and implement.
A, B, C, & D are inputs of a counter. Z is the output and is to be High for counts of 0,1,2,3,5,7,11, and 15. Designt the circuit.

I've made the truth table, created the SOP expression... but I dont know how to simplify this expression. It's soooo long, LOL:

Z = ~A~B~C~D + ~A~B~CD + ~A~BC~D + ~A~BCD + ~AB~CD + ~ABCD + A~BCD +ABCD

robyrob · 01-22-2006, 07:26 PM

im gonna say that that is beyond what I can remember how to simplify, but it looks like you should be able to simplify it

maybe this can help:

Boolean rules for simplification http://www.allaboutcircuits.com/vol_4/chpt_7/5.html

Circuit simplification examples http://www.allaboutcircuits.com/vol_4/chpt_7/6.html

Warm & Fuzzy · 01-23-2006, 01:03 AM

Thanks for the sites, Rob.

I've given up on trying to simplify it, though, haha. I've spent the last five days preparing for my computer science finals. I think I need to rest before I drop dead!

BTW, I was wondering, do/did you major in computer science. And if you have, what courses do you take or have taken?

Comp sci is currently my major - has been for two years - but I'm thinking about switching 'cause it's driving me crazy. Too many logical-stuff, LOL. I've taken/am taking: A+ Certification, Database Management w/ Access, Java, VB.Net, PHP, HTML, DDL, SQL, Networking, computer architecture, blah blah.

Just curious.

robyrob · 01-23-2006, 01:16 AM

i did Architecture then Math/Computing Science - this was many years ago though

i remember they made me take philosphy and other weird, seemingly-unrelated courses, and I always had problems getting into classes because they were too full, I had to take some prerequisite courses after i finished the courses that required them

hang in there, its supposed to be hard, otherwise everyone would be doing it

Warm & Fuzzy · 01-23-2006, 01:30 AM

Of all things - philosophy? LOL. Sometimes I wonder if schools really know what they're doing.

I'm still a senior in High School [majoring in college Computer Science], so I'll be graduating this June. Given that, I have the option of changing my major and starting 'fresh' in college, and still not be behind the rest of the freshman class.

But, if I do decide to change my major, I would have "wasted" two years, you know?

On the other hand, I really despise computer science. It's arduous.

01-22-2006, 02:51 PM	#1
Warm & Fuzzy Member Forum Fanatic Join Date: Feb 02, 2001 Posts: 10,254	(computers) Need help w/ Homework Can someone help me with this problem, please? It's computer architecture, and I've been stuck with it for the longest of time. Thanks in advance! Attached Images

01-22-2006, 06:42 PM	#2
robyrob certified wackball#3 Moderator Forum Icon Join Date: Aug 03, 2003 Location: hiding under the third booth at Arnold's Posts: 58,211	its been a long time since i messed with any boolean logic expressions but I'll try to help; i wasn't familiar with the notation that uses the bar over the top of each letter to indicate a negative or false expression, but if you convert it to a conventional expression (using ~ to indicate negation): ~(~a + ~b + ~cd~e) + ~(~bc~d) NOT(NOTa AND NOTb AND NOTc AND d AND NOTe) AND NOT(NOTb AND c AND NOTd) you may want to draw a map or truth tables first http://dept-info.labri.u-bordeaux.fr...ial/gates.html http://cnx.rice.edu/content/m13240/latest/ http://www.gamezero.com/team-0/artic...o/boolean.html i dont remember enough to tell if you can reduce it further, (for example ~(~a AND ~b) = a OR b ) but I really dont know what your teacher is looking for...
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01-22-2006, 06:51 PM	#3
Warm & Fuzzy Member Forum Fanatic Join Date: Feb 02, 2001 Posts: 10,254	AHHH!! My savior! bows down to thee LOL. Let's see... this is what I have written down... is it in "simplest form," though? Like, is this the least number of gates that I can use? Or can I use even LESS? (I can only use AND, OR, and INVERTER). I used 14, I believe. And I prefer to use the bar to indicate an inverse because it takes up less space when writing, LOL. The '~' symbol takes up the space of a character, and I am limited to an 8x11" paper, hehe. Oh, and I also need assistance in one more question, LOL. Design: Use truth tables, SOP expression, simplify and implement. A, B, C, & D are inputs of a counter. Z is the output and is to be High for counts of 0,1,2,3,5,7,11, and 15. Designt the circuit. I've made the truth table, created the SOP expression... but I dont know how to simplify this expression. It's soooo long, LOL: Z = ~A~B~C~D + ~A~B~CD + ~A~BC~D + ~A~BCD + ~AB~CD + ~ABCD + A~BCD +ABCD Attached Images

01-22-2006, 07:26 PM	#4
robyrob certified wackball#3 Moderator Forum Icon Join Date: Aug 03, 2003 Location: hiding under the third booth at Arnold's Posts: 58,211	im gonna say that that is beyond what I can remember how to simplify, but it looks like you should be able to simplify it maybe this can help: Boolean rules for simplification http://www.allaboutcircuits.com/vol_4/chpt_7/5.html Circuit simplification examples http://www.allaboutcircuits.com/vol_4/chpt_7/6.html

01-23-2006, 01:03 AM	#5
Warm & Fuzzy Member Forum Fanatic Join Date: Feb 02, 2001 Posts: 10,254	Thanks for the sites, Rob. I've given up on trying to simplify it, though, haha. I've spent the last five days preparing for my computer science finals. I think I need to rest before I drop dead! BTW, I was wondering, do/did you major in computer science. And if you have, what courses do you take or have taken? Comp sci is currently my major - has been for two years - but I'm thinking about switching 'cause it's driving me crazy. Too many logical-stuff, LOL. I've taken/am taking: A+ Certification, Database Management w/ Access, Java, VB.Net, PHP, HTML, DDL, SQL, Networking, computer architecture, blah blah. Just curious.

01-23-2006, 01:16 AM	#6
robyrob certified wackball#3 Moderator Forum Icon Join Date: Aug 03, 2003 Location: hiding under the third booth at Arnold's Posts: 58,211	i did Architecture then Math/Computing Science - this was many years ago though i remember they made me take philosphy and other weird, seemingly-unrelated courses, and I always had problems getting into classes because they were too full, I had to take some prerequisite courses after i finished the courses that required them hang in there, its supposed to be hard, otherwise everyone would be doing it

01-23-2006, 01:30 AM	#7
Warm & Fuzzy Member Forum Fanatic Join Date: Feb 02, 2001 Posts: 10,254	Of all things - philosophy? LOL. Sometimes I wonder if schools really know what they're doing. I'm still a senior in High School [majoring in college Computer Science], so I'll be graduating this June. Given that, I have the option of changing my major and starting 'fresh' in college, and still not be behind the rest of the freshman class. But, if I do decide to change my major, I would have "wasted" two years, you know? On the other hand, I really despise computer science. It's arduous.