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

Parallels Desktop 10.2.0 - Run Windows a...
Parallels Desktop is simply the world's bestselling, top-rated, and most trusted solution for running Windows applications on your Mac. With Parallels Desktop for Mac, you can seamlessly run both... Read more
LaunchBar 6.2 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Firefox 37.0 - Fast, safe Web browser. (...
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
Arq 4.11 - Online backup to Google Drive...
Arq is super-easy online backup for the Mac. Back up to your own Google Drive storage (15GB free storage), your own Amazon Glacier ($.01/GB per month storage) or S3, or any SFTP server. Arq backs up... Read more
MacFamilyTree 7.3.4 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Yummy FTP 1.10.2 - FTP/SFTP/FTPS client...
Yummy FTP is an FTP + SFTP + FTPS file transfer client which focuses on speed, reliability and productivity. Whether you need to transfer a few files or a few thousand, schedule automatic backups, or... Read more
VueScan 9.5.08 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Iridient Developer 3.0.1 - Powerful imag...
Iridient Developer (was RAW Developer) is a powerful image conversion application designed specifically for OS X. Iridient Developer gives advanced photographers total control over every aspect of... Read more
Monodraw 0.8.4.1 - Powerful ASCII art ed...
Monodraw allows you to easily create text-based art (like diagrams, layouts, flow charts) and visually represent algorithms, data structures, binary formats and more. Because it's all just text, it... Read more
Air Video Server HD 2.1.0 - Stream video...
Air Video Server HD streams videos instantly from your computer on your iPhone, iPad, iPod touch or Apple TV. No need to worry about converting or transferring files. We took everything that was... Read more

2K Announces WWE 2K, Mobile's First...
It seems like this month has been pretty big for wrestling. First Wrestlemania, then 2K has announces that they're releasing  WWE 2K for iOS. It's a simulation-based WWE game where you'll get to play with several WWE superstars such as John Cena, ... | Read more »
How the Apple Watch Could Change the Fac...
The Apple Watch is still a ways out, but my previous musings on the wearable’s various features got me thinking: what might it be like a year after launch? Two years? Five years? What if it becomes a symbiotic part of the iOS framework to the point... | Read more »
Pie In The Sky: A Pizza Odyssey (Games)
Pie In The Sky: A Pizza Odyssey 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A game about delivering pizza. In space. | Read more »
Chosen Gives Hopeful Singers, Songwriter...
If YouTube videos and reality TV shows like The Voice have taught us one thing, it’s that there are a lot of people out there who are anxious to show the world their talents. And if they’ve taught us a second thing, it’s that there’s an almost... | Read more »
Android's Popular OfficeSuite Now A...
Once only available for Android devices, OfficeSuite has finally landed on the app store. The Mobile Systems app lets you view, edit, create, and share Word, Excel, and PowerPoint documents as well as convert them to/from PDFs. It's touted as being... | Read more »
Warhammer: Arcane Magic is Coming Soon,...
Turbo Tape Games has announced that they're joining forces with Games Workshop to bring the turn-based strategy board game, Warhammer: Arcane Magic, to life on the iOS. | Read more »
Fast & Furious: Legacy's Creati...
| Read more »
N-Fusion and 505's Ember is Totally...
| Read more »
These are All the Apple Watch Apps and G...
The Apple Watch is less than a month from hitting store shelves, and once you get your hands on it you're probably going to want some apps and games to install. Fear not! We've compiled a list of all the Apple Watch apps and games we've been able to... | Read more »
Appy to Have Known You - Lee Hamlet Look...
Being at 148Apps these past 2 years has been an awesome experience that has taught me a great deal, and working with such a great team has been a privilege. Thank you to Rob Rich, and to both Rob LeFebvre and Jeff Scott before him, for helping me... | Read more »

Price Scanner via MacPrices.net

13-inch 2.4GHz Retina MacBook Pro available f...
MacMall has the 2013 13″ 2.4GHz/128GB Retina MacBook Pro available for $949.99 for a limited time. Shipping is free. Their price is $350 off original MSRP, and it’s the only sub-$1000 new Retina... Read more
Adobe Brings Powerful Layout-Design Capabilit...
Adobe today announced the availability of Adobe Comp CC, a free iPad app that enables rapid creation of layout concepts for mobile, Web and print projects. With Comp CC, designers can rough out and... Read more
13-inch 2.6GHz/256GB Retina MacBook Pro avail...
Best Buy has clearance 2014 13″ 2.6GHz/256GB Retina MacBook Pros available for $1199.99 including free shipping. Their price is $300 off original MSRP, and it’s the lowest price for this model.... Read more
Updated Mac Price Trackers
We’ve updated our Mac Price Trackers with the latest information on prices, bundles, and availability on systems from Apple’s authorized internet/catalog resellers: - 15″ MacBook Pros - 13″ MacBook... Read more
21-inch 1.4GHz iMac on sale for $999, save $1...
Best Buy has the 21″ 1.4GHz iMac on sale for $999.99 on their online store. Choose free shipping or free local store pick up. Price is for online orders only, in-store prices may vary. Their price is... Read more
2.6GHz Mac mini on sale for $649, save $50
Amazon has the 2.6GHz Mac mini on sale for $649.99 including free shipping. Their price is $50 off MSRP, and it’s the lowest price available for this model. Read more
Textkraft Professional 3.2 Powerful iPad Text...
Finally it’s springtime, at least theoretically in my neck of the woods, where we’re still navigating canyons between towering snowbanks with temperatures well below freezing in winter weather that... Read more
Apple offering refurbished 27-inch 5K iMacs f...
The Apple Store is offering Apple Certified Refurbished 27″ 3.5GHz 5K iMacs for $2119 including free shipping. Their price is $380 off the price of new models, and it’s the lowest price available for... Read more
16GB iPad mini on sale for $199, save $50
Walmart has 16GB iPad minis (1st generation) available for $199.99 on their online store, including free shipping. Their price is $50 off MSRP. Online orders only. Read more
New 128GB MacBook Airs on sale for $50 off MS...
 B&H Photo has 128GB 11″ and 13″ 2015 MacBook Airs on sale today for $50 off MSRP including free shipping plus NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air (Model #MJVM2LL/A): $849 $50 off... Read more

Jobs Board

DevOps Software Engineer - *Apple* Pay, iOS...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Lead *Apple* Solutions Consultant - Retail...
**Job Summary** Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer in a hyper-business critical Reseller's store Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.