TweetFollow Us on Twitter

Segment
Volume Number:2
Issue Number:11
Column Tag:Basic School

Using the Segment Manager from Basic

By Dave Kelly, MacTutor Editorial Board

This month we'll discuss Macintosh memory management (part 2, part 1 was discussed back in the June 1985 MacTutor). While the information back in June 1985 is still valid, there are some other (new?) considerations that I haven't mentioned yet. If you have the June '85 MacTutor go back and review that information as it will be useful here as we talk about it some more. It would also be helpful to read Inside Macintosh Vol. I chapter 3 on Memory Management and Vol II chapter 2 on the Segment Loader.

Now that we have as much memory available as we ever dreamed we might have (remember when it was so great to have 16K RAM?), we need to talk about the best ways to make use of it. In review, please recall that the key to memory management in MS Basic is the CLEAR statement. Even on a Macintosh Plus you should use CLEAR to make the best use of the available memory. The following procedure will help you to quickly set up the memory configuration:

1. Load your program and before running it type PRINT FRE(0) in the command window to determine the amount of memory used by your program listing. Record this number for later use.

2. Run the program. The intent here is to determine the amount of memory that your variables need. For some programs you may not be able to run enough of the program to declare all of the variables. In that case you may have to do some rough guessing here. Either after running your program or sometime during the program (this may be more convenient) you should print FRE(0) again. The difference between this number and the number you recorded in step 1 above is the amount of memory allocated to the data segment that is used for your variables. (FRE(-1) returns the number of bytes not used in the heap; FRE(-2) returns the number of bytes in the stack that have not been used; you may use these if it will help you).

3. Now it's time to guess. Try to decide if the program will ever need more memory than this in the future. If you need to increase the program size later or allocate more variables you will need to allow some space for this. If you are not sure you may want to just add 20% or so more memory to the length of the program. Whatever you decide here will be your data segment memory.

4. Now, if your program uses any Macintosh resources you will need to figure out how much of the heap to use. If you have extra memory like on the Mac plus it never hurts to have extra heap space. In fact, the heap may be more heavily used than the data segment depending on how many controls, or windows, etc. you may be using. Keep in mind also that if any desk accessories are opened they will need some heap space of their own. By printing FRE(-2) it will show the heap memory allocation. If you print FRE(-2) before running the program you will know the amount of heap available to the program. After the program is run and resources are loaded, the amount of heap will decrease. You need to know the difference between the FRE(-2) before and after running the program. Record this number.

5. Now you need to calculate the stack-size to use in the CLEAR statement. Many times it is not even necessary to change the data segment (leave it as large as the memory you have left). The number to use for the stack-size is calculated by stack-size = Total Ram - (data-segment-size + heap-size).

Fig. 1 Output of our Segment Program

Now how do you know when you need to adjust the memory allocation? Ans: Anytime that you notice an unusual amount of disk activity, especially just before displaying controls (edit fields, buttons, menus, windows etc.). It doesn't matter if you have a Mac Plus or not, if you don't adjust your memory properly, then the memory will not be used efficiently. In order to remain compatible with the 512K & 128K Mac, the heap and stack default sizes are the same on the Mac plus. This may explain why so many Mac programs need to read the disk so often even though you may think you have a lot of memory (1Meg really is plenty for Basic!!). Good memory management planning can improve your program tremendously. Another thing to keep in mind is that once the CLEAR statement has been used to change the memory allocation it will remain that way for the next program that you load into memory. A second CLEAR statement will not reallocate the memory properly. It is best to quit to the finder and start all over unless the new program uses the same memory configuration.

So much for MS Basic memory management. The comments above in addition to those in the June '85 MacTutor should give you all you need to handle most of your memory management. Memory management in other languages is handled through use of the Segment Loader. Access to the Segment Loader is not provided in MS Basic. ZBasic provides the SEGMENT and SEGMENT RETURN statements which use the Segment Loader. We'll talk about those in a moment. First a few words about the Segment Loader. The Segment Loader allows you to divide up the code of your application into several parts. When the Finder starts up your application the Segment Loader is called to load in the main segment of your program. Other segments are loaded in automatically as needed. After a segment is no longer needed, your application can call the segment loader to make the segment purgable. This way if you have only a small amount of memory available you may still run a large program. The maximum size of a segment is 32K. Any code that is not used often may be in a separate segment so that it may be swapped in whenever it is needed. Another function of the Segment Loader is in supplying information from the Finder.

Your ZBasic code will be compiled into code segments (resources of type 'CODE') automatically, no matter if you use the SEGMENT statements or not. When the code reaches a length of about 28K the segment will end and the next segment will be loaded. The SEGMENT RETURN statement marks the end of the CODE segment and returns to the calling routine (cannot be called from the same segment). You should arrange your application such that a segment consists of a subroutine. The routines you decide to separate into segments preferably should be routines which are only used occasionally (example: print routines).

The following example program demonstrates how to "segmentize" your programs. However, because the segments in the example are small (less than 100 bytes), the segment memory swapping is virtually non-existent on a Macintosh plus (and probably all the other size Macs too!). If you really want to try this out, you'll have to write some larger CODE segments and run on a smaller Mac. You can check the segment sizes by choosing the COMPILE option of the ZBasic command menu. The sizes of the segments will be displayed. The remaining memory can be found with the MEM(-1) function. MEM(-1) returns the maximum amount of available memory for the program and variables.

Another part of the Segment Loader is supported by ZBasic with the FINDERINFO function. The FINDERINFO function returns information to your application which tells the application how the application was selected from the Finder. The function returns variables with the number of files selected, the name of the files and volume number, and a message variable indicating if the file should be loaded or printed. This way the files may be printed (or whatever) without going through the full set of initialization routines that your application may have. If no files have been selected then your application should open a new untitled document and continue from there. The syntax is: message%= FINDERINFO (count%, var$[(n)], type%[(n)], volume%[(n)]). The message variable is the result of the FINDERINFO function. If the result is equal to zero then the file should be loaded otherwise the file should be printed. The Count% variable returns the number of files . The variable var$(n) is a string variable or string array with the names of the files which have been selected. The file type of the selected files is stored in a long integer word which must be converted to a string by using the MKI$ statement. The volume% variable is the the disk volume where the file is located.

To get the FINDERINFO function to work, first you must compile your program as an application. There are two or three statements that must be used properly in order to compile the program so that the function will work. First type CREATOR "ffff" where "ffff" is the creator name which will be given to the application. The other statement that must match this one is the DEFOPEN "ffffcccc" statement which sets up the file type ("ffff") and the file creator ("cccc") for the data files created by your application. In the demo program the creator is "DAVE" and the file type is "DATA". The DEFOPEN statement is used in the application program when opening up new data files. Now that the creator is the same for the application as for the data, we need to set the bundle bit with the BUNDLE 1 statement. Type BUNDLE 1 in the command window. Now it is time to compile the program into an application. Select RUN* from the menus to create the application. New data files which are created with the application will now be linked to each other. Selecting one or more data files while in the Finder and selecting PRINT or OPEN will open the application which the data files belong and send info to the application via the FINDERINFO statement. To see the results of this function, you may want to run the demo and create a few sample data files and see what happens when they are selected for printing or to be opened.

If you have problems getting the FINDERINFO information, be sure that you set the creator and bundle bit before compiling the application. You should also be sure to define all the variables in the function before calling it. More information on the Segment Loader is available in Vol 2, Chap. 2 of Inside Macintosh (The Segment Loader chapter).

WINDOW OFF
REM Segment Loader Example ZBasic 3.02
REM ©MacTutor 1986
REM by Dave Kelly
DIM 31 Name$(5),Vol%(5),Type&(5),Mes$(1)
REM up to 5 files can be selected.
DEFSTR LONG
Count%=2
Message%=FINDERINFO(Count%, Name$(0), Type&(0),    Vol%(0))
X&=MEM(-1)
WINDOW 1,"Segment Sample",(50,100)-(475,300),257
IF Count%<>0 THEN GOSUB "DisplayFINDERINFO"
MENU 1,0,1,"File"
MENU 1,1,1,"Create Data File"
MENU 1,2,1,"Quit"
MENU 2,0,1,"Segments"
MENU 2,1,1,"Main Segment"
MENU 2,2,1,"1st Segment"
MENU 2,3,1,"2nd Segment"
MENU 2,4,1,"3rd Segment"
MENU 2,5,1,"Check memory available and unload unused     segments"
ON MENU GOSUB "Menuevent"
MENU ON
"Loop":
GOTO "Loop"
"Menuevent":
Menunumber=MENU(0)
Menuitem=MENU(1)
MENU
MENU OFF
ON Menunumber GOSUB "Filemenu","Segmenu"
MENU ON
RETURN
"Filemenu":
IF Menuitem=1 THEN "Openfile"
IF Menuitem<>2 THEN RETURN
MENU RESET
END
"Openfile":
DEF OPEN "DATADAVE"
Filename$=FILES$(0,"Create new file as ..." ,"Segment    DATA")
IF Filename$="" THEN RETURN
OPEN O,#1,Filename$
PRINT "New file named ";Filename$;" has been created.":PRINT
PRINT "Quit the program and click on "; Filename$; " to see    how the"
PRINT "FINDERINFO function works.  Select PRINT or OPEN  from the Finder."
PRINT "The FINDERINFO function will indicate what has been     selected."
PRINT "You may want to create multiple data files and try      printing"
PRINT "or opening them to see what happens."
RETURN
"Segmenu":
ON Menuitem GOSUB "Main", "Seg1", "Seg2", "Seg3",  "Memory"
RETURN
"Main":
PRINT "This is part of the main segment"
RETURN
SEGMENT
"Seg1"
PRINT "This is part of the 1st segment"
SEGMENT RETURN
SEGMENT
"Seg2"
PRINT "This is part of the 2nd segment"
SEGMENT RETURN
SEGMENT
"Seg3"
PRINT "This is part of the 3rd segment"
SEGMENT RETURN
SEGMENT
"Memory"
X&=MEM(-1)
PRINT "Memory = ";X&
SEGMENT RETURN
SEGMENT
"DisplayFINDERINFO":
CLS
Mes$(0)="Data file(s) should be loaded"
Mes$(1)="Data file(s) should be printed"
PRINT "Message% = ";Message%;" Therefore... "; Mes$(     Message%)
PRINT "Count%   = ";Count%; "file(s) have been passed to       this application"
PRINT "Filenames are:"
PRINT"Name","Type","Vol"
FOR C=0 TO Count%-1
PRINT Name$(C),MKI$(Type&(C)),Vol%(C)
NEXT C
SEGMENT RETURN
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Hopper Disassembler 4.3.10- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
Paparazzi! 1.0b7 - Make user-defined siz...
Paparazzi! is a small utility for OS X that makes screenshots of webpages. This very simple tool takes screenshots of websites which do not fit on one screen. You specify the desired width, minimal... Read more
Amadeus Pro 2.4.4 - Multitrack sound rec...
Amadeus Pro lets you use your Mac for any audio-related task, such as live audio recording, digitizing tapes and records, converting between a variety of sound formats, etc. Thanks to its outstanding... Read more
Google Chrome 63.0.3239.108 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
Apple Configurator 2.6 - Configure and d...
Apple Configurator makes it easy to deploy iPad, iPhone, iPod touch, and Apple TV devices in your school or business. Use Apple Configurator to quickly configure large numbers of devices connected to... Read more
WhatRoute 2.0.26 - Geographically trace...
WhatRoute is designed to find the names of all the routers an IP packet passes through on its way from your Mac to a destination host. It also measures the round-trip time from your Mac to the router... Read more
Remotix 5.0.4 - Access all your computer...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features Complete Apple Screen Sharing support - including Mac OS X login, clipboard... Read more
WhatRoute 2.0.26 - Geographically trace...
WhatRoute is designed to find the names of all the routers an IP packet passes through on its way from your Mac to a destination host. It also measures the round-trip time from your Mac to the router... Read more
Google Chrome 63.0.3239.108 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
Paparazzi! 1.0b7 - Make user-defined siz...
Paparazzi! is a small utility for OS X that makes screenshots of webpages. This very simple tool takes screenshots of websites which do not fit on one screen. You specify the desired width, minimal... Read more

Latest Forum Discussions

See All

WWE Mayhem guide - beginner tips and tri...
WWE Mayhem brings all of the familiar faces from your favorite wrestling league to mobile in this exciting new fighting game. Build up a team of your favorite WWE superstars and fight your way to the championship title, or battle against your... | Read more »
The best new games we played this week -...
We've made it through another week, so let's treat ourselves to some of the best new games to launch in the past few days. It was another exciting week with some long-awaited indie games making their debut, and some big console titles making the... | Read more »
Match blocks to pull off dance moves in...
Ferdinand: Unstoppabull is a brand new match three puzzler based on the animated movie of (almost) the same name. As you can expect, you have to match blocks together to complete a bunch of puzzling levels and earn a high score. [Read more] | Read more »
Lineage 2: Revolution’s end of year upda...
Now available in 54 countries worldwide, Lineage 2: Revolution is continuing its global quest to be the most popular mobile MMORPG by launching a jam-packed end of year update. Complete with many subtle tweaks to help improve users’ online... | Read more »
The 5 best Star Wars games on iOS
The time has almost come.Star Wars: The Last Jedifinally hits theaters in the cinematic event that might be bigger than Christmas. To celebrate, we're taking a look at the best--and only the best--Star Warsmobile games to date. [Read more] | Read more »
Life Is Strange (Games)
Life Is Strange 1.1 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1 (iTunes) Description: Life Is Strange is a five part episodic game that sets out to revolutionize story-based choice and consequence games by... | Read more »
Oddworld: New 'n' Tasty (Game...
Oddworld: New 'n' Tasty 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: ** PLEASE NOTE: Requires 3.6GB free space to install. Runs at variable resolutions based on device capabilities.... | Read more »
Gorogoa (Games)
Gorogoa 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Gorogoa is an elegant evolution of the puzzle genre, told through a beautifully hand-drawn story designed and illustrated by Jason... | Read more »
Why Guns of Boom will be big for mobile...
Earlier this week, Game Insight, the minds that brought you Guns of Boom, revealed plans for an esports mode in the popular FPS title, with big implications for the game's future. Guns of Boom has been quite popular for some time now, so it's... | Read more »
The best mobile games to play on lazy ho...
With the holidays in full swing, there's hopefully going to be a lot of time off work lazing around the house. With all of that free time, it's a perfect opportunity to catch up on some mobile games that you might have missed out on earlier this... | Read more »

Price Scanner via MacPrices.net

The lowest prices on Apple 13″ MacBook Pros t...
Save $300-$300 on the purchase of a 2017 13″ MacBook Pro this weekend with Certified Refurbished models at Apple. In many cases, Apple’s refurbished prices are the lowest available for each model... Read more
Lowest prices of the Holiday season: 15″ Appl...
Save $360-$420 on the purchase of a 2017 15″ MacBook Pro with Certified Refurbished models at Apple. In many cases, Apple’s refurbished prices are the lowest available for each model from any... Read more
Apple discounts Beats products by up to 30% t...
Apple has Beats by Dr. Dre (BeatsX, Powerbeats3 Wireless, and Beats Solo3 Wireless) on sale for up to 30% off their retail price from now until December 26th: – BeatsX: Was $149.95, now $99 –... Read more
Updated Price Trackers: Macs, iPads, iPhones,...
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: – 15″... Read more
How to preorder a new iMac Pro and pay zero s...
B&H Photo and Adorama are accepting preorders on multiple configurations of the new Apple iMac Pro. Both resellers charge sales tax for residents of NY & NJ only, and shipping is free.... Read more
Apple Macs back in stock at Amazon with model...
Amazon has MacBook Pros, MacBook Airs, MacBooks, and iMacs on sale for up to $200 off MSRP as part of their Holiday/Christmas sale. Shipping is free. Note that stock of some Macs may come and go (and... Read more
Apple offering free overnight delivery on all...
Apple is now offering free overnight delivery on all in stock products until 3pm local time on December 22nd. This includes new as well as refurbished computers. Click here for more information. Read more
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

Jobs Board

*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* 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
Payments Counsel, *Apple* Pay (payments, cr...
# Payments Counsel, Apple Pay (payments, credit/debit) Job Number: 112941729 Santa Clara Valley, California, United States Posted: 13-Dec-2017 Weekly Hours: 40.00 Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 113124408 Waterford, CT, Connecticut, United States Posted: 17-Oct-2017 Weekly Hours: 40.00 **Job Summary** Are you Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.