TweetFollow Us on Twitter

Screen Pokes
Volume Number:1
Issue Number:5
Column Tag:BASIC

Professor Mac’s Screen Pokes

By Dave Kelly

Mike Steiner and Michael M. Boy contributed to this article and we acknowledge their valuable con- tributions.

Professor Mac’s Screen Pokes

One day, Professor Mac was poking around in his Mac’s memory when suddenly he fell in and got stuck. Then along came Mike Steiner with screen memory locations. Professor Mac was then able to write his own program to poke his head out of the Mac screen.

The upper left corner of the screen starts at 108288. The locations progress consecutively starting from the upper left corner of the screen to the bottom right corner moving left to right and down the screen. The bottom right corner of the screen is 130175. These locations are for a 128K Mac. Add (512-128)*1024 for a 512K Mac. Be careful to not poke locations before or after the start and end addresses... unpredictable things will happen.

There are 21888 locations mapping the Macintosh screen. Each line (342 lines) of the screen is represented by 64 memory locations. Thus the first line of the screen goes from 108288 to 108351, the second line starts at 108352 and so on.... (remember to add for 512K Mac)

Each memory location contains 1 sixteen bit word which is bit mapped on the Mac screen. From left to right on the screen, the sixteen bits are mapped from hi order bit to low. A typical memory location is shown in figure 1.

The program pokes zeros into the first 18 lines of the screen, hiding the BASIC menu bars. The menus are still active and can be used to trace or stop the program. The image of Professor Mac is read from data statements and poked into the screen memory locations. Most of the time, you probably won’t want to poke the screen directly, there are easier ways to print on the screen. But this method could be used to check status of a particular location of the screen. The FRE(0) command is used to check which Mac (128K or 512K) is being used because the start and ending screen locations are different and have to be adjusted for the 512K Mac.

Thanks and appreciation go to Mike Steiner of Sierra Vista, Az. and Michael M. Boy of Elgin, Az. for submitting the screen locations.

‘Professor Mac’s Screen Poke
‘By Dave Kelly

WINDOW CLOSE 1
start=108288!  ‘Starting address for 128K MAC
ending=130175! ‘Ending address for 128K 

mac512=(512-128)*1024  ‘address offset for 512K MAC
IF FRE(0)>100000! THEN  start=start+mac512: ending=ending+mac512
erase.top.of.screen:
    FOR i= start TO start +64*18
        POKE i,0
    NEXT i
WINDOW  1
TEXTFONT(2):TEXTSIZE(18)
LOCATE 8,10:PRINT “Prof. Mac says: Read MacTutor!”
TEXTSIZE(12):PRINT
PRINT TAB(22);”Hit mouse button to quit”
print.professor.mac:
a=start+64*100 ‘Start at line 100
b=67  ‘print 67 lines 
FOR j=a TO a+b*64 STEP 64
    FOR k= j+30 TO j+36
        READ value
        POKE k,value
    NEXT k
NEXT j
ON MOUSE GOSUB quit
MOUSE ON:RESTORE
GOTO print.professor.mac
quit:
MENU RESET:END
prof.mac.plot.data:
1   DATA &H00,&H00,&H00,&HE0,&H00, &H00,&H00
2   DATA &H00,&H00,&H01,&HF8,&H00, &H00,&H00
3   DATA &H00,&H00,&H07,&HFC,&H00, &H00,&H00
4   DATA &H00,&H00,&H0F,&HFF,&H00, &H00,&H00
5   DATA &H00,&H00,&H3F,&HFF,&HC0, &H00,&H00
6   DATA &H00,&H00,&H7F,&HFF,&HE0, &H00,&H00
7   DATA &H00,&H01,&HFF,&HFF,&HF8, &H00,&H00
8   DATA &H00,&H03,&HFF,&HFF,&HFE, &H00,&H00
9   DATA &H00,&H07,&HFF,&HFF,&HFF, &H80,&H00
10 DATA &H00,&H1F,&HFF,&HFF,&HFF,  &HC0,&H00
11 DATA &H00,&H3F,&HFF,&HFF,&HFF,  &HF0,&H00
12 DATA &H00,&HFF,&HFF,&HFF,&HFF,  &HFC,&H00
13 DATA &H01,&HFF,&HFF,&HF3,&HFF,  &HFE,&H00
14 DATA &H03,&HFF,&HFF,&HE1,&HFF,  &HFF,&H80
15 DATA &H07,&HFF,&HFF,&HE1,&HFF,  &HFF,&HC0
16 DATA &H0F,&HFF,&HFF,&HF2,&H7F,  &HFF,&HC0
17 DATA &H1F,&HFF,&HFF,&HFF,&H9F,  &HFF,&H80
18 DATA &H0F,&HFF,&HFF,&HFF,&HE7,  &HFF,&H00
19 DATA &H07,&HFF,&HFF,&HFF,&HF9,  &HFE,&H00
20 DATA &H01,&HFF,&HFF,&HFF,&HFE,  &H7C,&H00
21 DATA &H03,&HFF,&HFF,&HFF,&HFF,  &H98,&H00
22 DATA &H03,&H3F,&HFF,&HFF,&HFF,  &HE8,&H00
23 DATA &H06,&H0F,&HFF,&HFF,&HFF,  &HFC,&H00
24 DATA &H06,&H07,&HFF,&HFF,&HFF,  &HFF,&HCC
25 DATA &H06,&H01,&HFF,&HFF,&HFF,  &H87,&H00
26 DATA &H06,&H00,&H7F,&HFF,&HFF,  &H0F,&H80
27 DATA &H06,&H00,&H1F,&HFF,&HFF,  &H0F,&H80
28 DATA &H06,&H00,&H0F,&HFF,&HFF,  &H0F,&H80
29 DATA  &H06,&H03,&H83,&HFF,&HFB, &H05,&H00
30 DATA &H06,&H07,&HC0,&HFF,&HF3,  &H00,&H00
31 DATA &H06,&H0F,&H60,&H3F,&HE3,  &H0A,&H80
32 DATA &H06,&H0E,&H30,&H1F,&HC3,  &H05,&H00
33 DATA &H06,&H0C,&H00,&H07,&H83,  &H02,&H00
34 DATA &H06,&H00,&H00,&H01,&H03,  &H08,&H80
35 DATA &H06,&H00,&H00,&H00,&H03,  &H05,&H00
36 DATA &H06,&H00,&H00,&H00,&H03,  &H00,&H00
37 DATA &H06,&H00,&H00,&H00,&H03,  &H0A,&H80
38 DATA &H06,&H80,&H70,&H70,&H0B,  &H05,&H00
39 DATA &H06,&H81,&HF8,&HFC,&H0B,  &H00,&H00
40 DATA &H06,&HC7,&HFD,&HFF,&H1B,  &H0A,&H80
41 DATA &H06,&H7F,&HFF,&HFF,&HF3,  &H00,&H00
42 DATA &H06,&H3F,&HFF,&HFF,&HE3,  &H1F,&H41
43 DATA &H03,&H07,&HFD,&HFF,&H06,  &H04,&H63
44 DATA &H03,&H81,&HF8,&HFB,&H0E,  &H04,&H55
45 DATA &H01,&HC0,&H00,&H00,&H1C,  &H04,&H49
46 DATA &H00,&HE0,&H00,&H00,&H38,  &H04,&H41
47 DATA &H00,&H7F,&HFF,&HFF,&HF0,  &H00,&H00
48 DATA &H00,&H1F,&HFF,&HFF,&HC0,  &H00,&H00
49 DATA &H00,&H08,&H00,&H00,&H40,  &H00,&H00
50 DATA &H00,&H08,&H00,&H00,&H40,  &H00,&H00
51 DATA &H00,&H0F,&HFF,&HFF,&HC0,  &H00,&H00
52 DATA &H00,&H1A,&HAA,&HAA,&HA0,  &H00,&H00
53 DATA &H00,&H35,&H55,&H55,&H50,  &H00,&H00
54 DATA &H00,&H6F,&HEA,&HFE,&HA8,  &H00,&H00
55 DATA &H00,&HD8,&H35,&H83,&H54,  &H00,&H00
56 DATA &H01,&HB0,&H1B,&H01,&HAA,  &H00,&H00
57 DATA &H03,&H50,&H15,&H01,&H55,  &H00,&H00
58 DATA &H06,&HA8,&H2A,&H82,&HAA,  &H80,&H00
59 DATA &H0D,&H57,&HD5,&H7D,&H7F,  &H40,&H00
60 DATA &H1A,&HFA,&HAF,&HAA,&HC1,  &HA0,&H00
61 DATA &H35,&H05,&H50,&H55,&H80,  &HD0,&H00
62 DATA &H6A,&H02,&HA0,&H2A,&H80,  &HA8,&H00
63 DATA &HD6,&H03,&H60,&H35,&H41,  &H54,&H00
64 DATA &HAB,&H06,&HB0,&H6A,&HBE,  &HAC,&H00
65 DATA &HD5,&HFD,&H5F,&HD5,&H55,  &H54,&H00
66 DATA &HAA,&HAA,&HAA,&HAA,&HAA,  &HAC,&H00
67 DATA &HD5,&H55,&H55,&H55,&H55,  &H54,&H00
68 DATA &HFF,&HFF,&HFF,&HFF,&HFF,  &HFC,&H00
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Civilization VI 1.0.6 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
djay Pro 2.0.1 - Transform your Mac into...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Microsoft OneNote 15.41 - Free digital n...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that's too important to forget. Whether you're at... Read more
TechTool Pro 9.6 - Hard drive and system...
TechTool Pro has long been one of the foremost utilities for keeping your Mac running smoothly and efficiently. With the release of version 9, it has become more proficient than ever. TechTool... Read more
Apple iOS 11.2.1 - The latest version of...
iOS 11 sets a new standard for what is already the world’s most advanced mobile operating system. It makes iPhone better than before. It makes iPad more capable than ever. And now it opens up both to... Read more
Things 3.3 - Elegant personal task manag...
Things is a task management solution that helps to organize your tasks in an elegant and intuitive way. Things combines powerful features with simplicity through the use of tags and its intelligent... Read more
RapidWeaver 7.5.5 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
Adobe Animate CC 2018 18.0.1.115 - Anima...
Animate CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Flash Professional customer). Animate CC 2018 (was Flash CC) lets you... Read more
Postbox 5.0.22 - Powerful and flexible e...
Postbox is a new email application that helps you organize your work life and get stuff done. It has all the elegance and simplicity of Apple Mail, but with more power and flexibility to manage even... Read more
Tunnelblick 3.7.4b - GUI for OpenVPN.
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more

Latest Forum Discussions

See All

Rules of Survival guide - how to boost y...
It's not easy surviving in the "every-man-for-himself" world of Rules of Survival. You'll be facing off against many other players who might be more skilled than you, or are luckier than you. There are a lot of factors weighing against you. With... | Read more »
FEZ Pocket Edition (Games)
FEZ Pocket Edition 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Amazing Katamari Damacy guide - beginner...
Amazing Katamari Damacy brings the bizarro world of the original games to mobile and shifts them into an endless format that's just as addictive as the PlayStation entries. Your goal is still to roll as much random stuff as you possibly can, though... | Read more »
Portal Knights guide - crafting tips and...
In Portal Knights, you're only as strong as the items you have at your disposal. This sandbox adventure is all about crafting and building up the next big thing. Whether you're an avid explorer or collector, crafting will likely play a large part... | Read more »
The best deals on the App Store this wee...
A new week means new discounts on the App Store. This week's deals run the gamut of action-adventure titles, puzzle games, and one of the best narrative adventure series out there. If you're looking to fill out your mobile gaming library on a... | Read more »
What you need to know about Animal Cross...
We hope you've been hard at work on collecting all of those holiday items in Animal Crossing: Pocket Camp, because you're about to get a whole new list of fun things to do as the game receives its first big update sometime soon. There are a lot of... | Read more »
Reigns: Her Majesty guide - how to use e...
Ruling a kingdom isn't easy--doubly so for a queen whose every decision is questioned by the other factions seeking a slice of power. Reigns: Her Majesty builds on the original game's swipey tactics, adding items that you can use to move the story... | Read more »
The best new games we played this week -...
Friday has crept up on us once again, so it's time to honor the best new games we've played over the past few days. This past week was a pretty exciting one, with the debut of lots of beautiful new indies and some familiar faces returning to the... | Read more »
Portal Knights guide- beginner tips and...
Portal Knights is finally making the jump to iOS and Android, and it's already climbing the ranks to become the next big MMO experience on mobile. This sprawling sandbox game will let you pursue any adventure you wish, whether you want to sling... | Read more »
Reigns: Her Majesty guide - how to swipe...
Reigns: Her Majesty is storming the App Store this week, bringing more tinder-esque kingdom building to eager players everywhere. If you've played the original Reigns, you'll know that leading a kingdom is never easy. It's a careful balancing act... | Read more »

Price Scanner via MacPrices.net

Beats Holiday sale at B&H, headphones and...
B&H Photo has Beats by Dr. Dre headphones, earphones, and speakers on sale for up to $80 off MSRP as part of their Holiday sale. Expedited shipping is free, and B&H charges sales tax to NY... Read more
Holiday sale: Apple resellers offer 2017 15″...
MacMall has 15″ MacBook Pros on sale for $220-$300 off MSRP, each including free shipping: – 15″ 2.8GHz MacBook Pro Space Gray (MPTR2LL/A): $2179, $220 off MSRP – 15″ 2.8GHz MacBook Pro Silver (... Read more
Holiday sale: Apple resellers offer 13″ MacBo...
B&H Photo has 13″ MacBook Pros on sale for up to $150 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 13-inch 2.3GHz/128GB Space Gray MacBook Pro (... Read more
Apple Watch Series 2, Certified Refurbished,...
Apple has Certified Refurbished Apple Watch Nike+ Series 2s, 42mm Space Gray Aluminum Case with Anthracite/Black Nike Sport Bands, available for $249 (38mm) or $279 (42mm). The 38mm model was out of... Read more
Apple offers Certified Refurbished 2016 12″ R...
Apple has Certified Refurbished 2016 12″ Retina MacBooks available starting at $949. Apple will include a standard one-year warranty with each MacBook, and shipping is free. The following... Read more
B&H drops price on 13″ 256GB MacBook Air...
B&H has the 13″ 1.8GHz/256GB Apple MacBook Air (MQD42LL/A) now on sale for $1079 including free shipping plus NY & NJ sales tax only. Their price is $120 off MSRP, and it’s the lowest price... Read more
Holiday sale: 9″ iPads starting at $299, take...
MacMall has 9″ WiFi iPads on sale for $30 off including free shipping: – 9″ 32GB WiFi iPad: $299 – 9″ 128GB WiFi iPad: $399 Read more
Green Monday deal: 15″ 2.8GHz MacBook Pro on...
B&H Photo has the 15″ 2.8GHz Space Gray MacBook Pro on sale for $250 off MSRP for today only as part of their Green Monday/Holiday sale. Shipping is free, and B&H charges sales tax for NY... Read more
Green Monday sale: B&H offers 12″ Apple i...
B&H Photo has 12″ iPad Pros on sale for up to $150 off MSRP as part of their Green Monday/Holiday sale. Shipping is free, and B&H charges sales tax in NY & NJ only: – 12″ 64GB WiFi iPad... Read more
Holiday deal: 21″ and 27″ Apple iMacs on sale...
MacMall has 2017 21″ and 27″ Apple iMacs on sale for up to $200 off MSRP. Shipping is free: – 21″ 2.3GHz iMac: $999 $100 off MSRP – 21″ 3.0GHz iMac: $1199 $100 off MSRP – 21″ 3.4GHz iMac: $1379 $120... Read more

Jobs Board

QA Automation Engineer, *Apple* Pay - Apple...
# QA Automation Engineer, Apple Pay Job Number: 113202642 Santa Clara Valley, California, United States Posted: 11-Dec-2017 Weekly Hours: 40.00 **Job Summary** At Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Information Security - Security Data...
# Apple Information Security - Security Data Analyst Job Number: 113119545 Austin, Texas, United States Posted: 10-Nov-2017 Weekly Hours: 40.00 **Job Summary** This Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.