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'About This Computer' Mac OS 9.1 window showing the memory consumption of each open application and the system software itself.
Historically, the classic Mac OS used a form of memory management that has fallen out of favor in modern systems. Criticism of this approach was one of the key areas addressed by the change to Mac OS X.
WhatsApp is rolling out a new and improved way to manage storage in the app, helping users identify, select and bulk delete GIFs, photos, and videos that may be filling up their phone. How to Manage Storage on Mac. By following the above-listed techniques, you would be able to clear disk space on Mac. Apart from that, you can also manage storage on Mac more efficiently by following these suggestions:. Manage iCloud Sync. By default, every Apple ID gets access to 5 GB of free storage on iCloud. May 17, 2019 Great tools to manage storage on Mac. There are plenty of third-party apps to manage storage on a MacBook. CleanMyMac X gives you a whole arsenal of tools to dig out junk. On average, Mac users find they gain an extra 62GB of storage that was lost to system junk files, outdated files, and apps that they didn't need anymore.
The original problem for the engineers of the Macintosh was how to make optimum use of the 128 KB of RAM with which the machine was equipped, on Motorola 68000-based computer hardware that did not support virtual memory.[1] Since at that time the machine could only run one application program at a time, and there was no fixedsecondary storage, the engineers implemented a simple scheme which worked well with those particular constraints. That design choice did not scale well with the development of the machine, creating various difficulties for both programmers and users.
Fragmentation[edit]
The primary concern of the original engineers appears to have been fragmentation - that is, the repeated allocation and deallocation of memory through pointers leading to many small isolated areas of memory which cannot be used because they are too small, even though the total free memory may be sufficient to satisfy a particular request for memory. To solve this, Apple engineers used the concept of a relocatable handle, a reference to memory which allowed the actual data referred to be moved without invalidating the handle. Apple's scheme was simple - a handle was simply a pointer into a (non relocatable) table of further pointers, which in turn pointed to the data.[2]If a memory request required compaction of memory, this was done and the table, called the master pointer block, was updated. The machine itself implemented two areas in memory available for this scheme - the system heap (used for the OS), and the application heap.[3]As long as only one application at a time was run, the system worked well. Since the entire application heap was dissolved when the application quit, fragmentation was minimized.
The memory management system had weaknesses; the system heap was not protected from errant applications, as would have been possible if the system architecture had supported memory protection, and this was frequently the cause of system problems and crashes.[4]In addition, the handle-based approach also opened up a source of programming errors, where pointers to data within such relocatable blocks could not be guaranteed to remain valid across calls that might cause memory to move. This was a real problem for almost every system API that existed. Because of the transparency of system-owned data structures at the time, the APIs could do little to solve this. Thus the onus was on the programmer not to create such pointers, or at least manage them very carefully by dereferencing all handles after every such API call. Since many programmers were not generally familiar with this approach, early Mac programs suffered frequently from faults arising from this.[5]
Palm OS and 16-bit Windows use a similar scheme for memory management, but the Palm and Windows versions make programmer error more difficult. For instance, in Mac OS, to convert a handle to a pointer, a program just de-references the handle directly, but if the handle is not locked, the pointer can become invalid quickly. Calls to lock and unlock handles are not balanced; ten calls to HLock are undone by a single call to HUnlock.[6] In Palm OS and Windows, handles are an opaque type and must be de-referenced with MemHandleLock on Palm OS or Global/LocalLock on Windows. When a Palm or Windows application is finished with a handle, it calls MemHandleUnlock or Global/LocalUnlock. Palm OS and Windows keep a lock count for blocks; after three calls to MemHandleLock, a block will only become unlocked after three calls to MemHandleUnlock.
Addressing the problem of nested locks and unlocks can be straightforward (although tedious) by employing various methods, but these intrude upon the readability of the associated code block and require awareness and discipline on the part of the coder.
Memory leaks and stale references[edit]
Awareness and discipline are also necessary to avoid memory 'leaks' (failure to deallocate within the scope of the allocation) and to avoid references to stale handles after release (which usually resulted in a hard crash—annoying on a single-tasking system, potentially disastrous if other programs are running).
Switcher[edit]
The situation worsened with the advent of Switcher, which was a way for a Mac with 512KB or more of memory to run multiple applications at once.[7] This was a necessary step forward for users, who found the one-app-at-a-time approach very limiting. Because Apple was now committed to its memory management model, as well as compatibility with existing applications, it was forced to adopt a scheme where each application was allocated its own heap from the available RAM.[8]The amount of actual RAM allocated to each heap was set by a value coded into the metadata of each application, set by the programmer. Sometimes this value wasn't enough for particular kinds of work, so the value setting had to be exposed to the user to allow them to tweak the heap size to suit their own requirements. While popular among 'power users', this exposure of a technical implementation detail was against the grain of the Mac user philosophy. Apart from exposing users to esoteric technicalities, it was inefficient, since an application would be made to grab all of its allotted RAM, even if it left most of it subsequently unused. Another application might be memory starved, but would be unable to utilize the free memory 'owned' by another application.[3]
While an application could not beneficially utilize a sister application's heap, it could certainly destroy it, typically by inadvertently writing to a nonsense address. An application accidentally treating a fragment of text or image, or an unassigned location as a pointer could easily overwrite the code or data of other applications or even the OS, leaving 'lurkers' even after the program was exited. Such problems could be extremely difficult to analyze and correct.
Switcher evolved into MultiFinder in System 4.2, which became the Process Manager in System 7, and by then the scheme was long entrenched. Apple made some attempts to work around the obvious limitations – temporary memory was one, where an application could 'borrow' free RAM that lay outside of its heap for short periods, but this was unpopular with programmers so it largely failed to solve the problems. Apple's System 7 Tune-up addon added a 'minimum' memory size and a 'preferred' size—if the preferred amount of memory was not available, the program could launch in the minimum space, possibly with reduced functionality. This was incorporated into the standard OS starting with System 7.1, but still didn't address the root problem.[9]
Virtual memory schemes, which made more memory available by paging unused portions of memory to disk, were made available by third-party utilities like Connectix Virtual, and then by Apple in System 7. This increased Macintosh memory capacity at a performance cost, but did not add protected memory or prevent the memory manager's heap compaction that would invalidate some pointers.
32-bit clean[edit]
Originally the Macintosh had 128 kB of RAM, with a limit of 512 kB. This was increased to 4 MB upon the introduction of the Macintosh Plus. These Macintosh computers used the 68000 CPU, a 32-bit processor, but only had 24 physical address lines. The 24 lines allowed the processor to address up to 16 MB of memory (224 bytes), which was seen as a sufficient amount at the time. The RAM limit in the Macintosh design was 4 MB of RAM and 4 MB of ROM, because of the structure of the memory map.[10] This was fixed by changing the memory map with the Macintosh II and the Macintosh Portable, allowing up to 8 MB of RAM.
Because memory was a scarce resource, the authors of the Mac OS decided to take advantage of the unused byte in each address. The original Memory Manager (up until the advent of System 7) placed flags in the high 8 bits of each 32-bit pointer and handle. Each address contained flags such as 'locked', 'purgeable', or 'resource', which were stored in the master pointer table. When used as an actual address, these flags were masked off and ignored by the CPU.[4]
While a good use of very limited RAM space, this design caused problems when Apple introduced the Macintosh II, which used the 32-bit Motorola 68020 CPU. The 68020 had 32 physical address lines which could address up to 4 GB (232 bytes) of memory. The flags that the Memory Manager stored in the high byte of each pointer and handle were significant now, and could lead to addressing errors.
In theory, the architects of the Macintosh system software were free to change the 'flags in the high byte' scheme to avoid this problem, and they did. For example, on the Macintosh IIci and later machines, HLock() and other APIs was rewritten to implement handle locking in a way other than flagging the high bits of handles. But, many Macintosh application programmers and a great deal of the Macintosh system software code itself accessed the flags directly rather than using the APIs, such as HLock(), which had been provided to manipulate them. By doing this they rendered their applications incompatible with true 32-bit addressing, and this became known as not being '32-bit clean'.
In order to stop continual system crashes caused by this issue, System 6 and earlier running on a 68020 or a 68030 would force the machine into 24-bit mode, and would only recognize and address the first 8 megabytes of RAM, an obvious flaw in machines whose hardware was wired to accept up to 128 MB RAM – and whose product literature advertised this capability. With System 7, the Mac system software was finally made 32-bit clean, but there were still the problem of dirty ROMs. The problem was that the decision to use 24-bit or 32-bit addressing has to be made very early in the boot process, when the ROM routines initialized the Memory Manager to set up a basic Mac environment where NuBus ROMs and disk drivers are loaded and executed. Older ROMs did not have any 32-bit Memory Manager support and so was not possible to boot into 32-bit mode. Surprisingly, the first solution to this flaw was published by software utility company Connectix, whose 1991 product MODE32 reinitialized the Memory Manager and repeated early parts of the Mac boot process, allowing the system to boot into 32-bit mode and enabling the use of all the RAM in the machine. Apple licensed the software from Connectix later in 1991 and distributed it for free. The Macintosh IIci and later Motorola based Macintosh computers had 32-bit clean ROMs.
It was quite a while before applications were updated to remove all 24-bit dependencies, and System 7 provided a way to switch back to 24-bit mode if application incompatibilities were found.[3] By the time of migration to the PowerPC and System 7.1.2, 32-bit cleanliness was mandatory for creating native applications and even later Motorola 68040 based Macs could not support 24-bit mode.[6][11]
Object orientation[edit]
The rise of object-oriented languages for programming the Mac – first Object Pascal, then later C++ – also caused problems for the memory model adopted. At first, it would seem natural that objects would be implemented via handles, to gain the advantage of being relocatable. These languages, as they were originally designed, used pointers for objects, which would lead to fragmentation issues. A solution, implemented by the THINK (later Symantec) compilers, was to use Handles internally for objects, but use a pointer syntax to access them. This seemed a good idea at first, but soon deep problems emerged, since programmers could not tell whether they were dealing with a relocatable or fixed block, and so had no way to know whether to take on the task of locking objects or not. Needless to say this led to huge numbers of bugs and problems with these early object implementations. Later compilers did not attempt to do this, but used real pointers, often implementing their own memory allocation schemes to work around the Mac OS memory model.
While the Mac OS memory model, with all its inherent problems, remained this way right through to Mac OS 9, due to severe application compatibility constraints, the increasing availability of cheap RAM meant that by and large most users could upgrade their way out of a corner. The memory wasn't used efficiently, but it was abundant enough that the issue never became critical. This is ironic given that the purpose of the original design was to maximise the use of very limited amounts of memory. Mac OS X finally did away with the whole scheme, implementing a modern sparse virtual memory scheme. A subset of the older memory model APIs still exist for compatibility as part of Carbon, but map to the modern memory manager (a threadsafe malloc implementation) underneath.[6]Apple recommends that Mac OS X code use malloc and free 'almost exclusively'.[12]
References[edit]
- ^Hertzfeld, Andy (September 1983), The Original Macintosh: We're Not Hackers!, retrieved 2010-05-10
- ^Hertzfeld, Andy (January 1982), The Original Macintosh: Hungarian, archived from the original on 2010-06-19, retrieved 2010-05-10
- ^ abcmemorymanagement.org (2000-12-15), Memory management in Mac OS, archived from the original on 2010-05-16, retrieved 2010-05-10
- ^ abHertzfeld, Andy, The Original Macintosh: Mea Culpa, retrieved 2010-05-10
- ^Apple Computer (1985-10-01), Technical Note OV09: Debugging With PurgeMem and CompactMem, retrieved 2010-05-10
- ^ abcLegacy Memory Manager Reference, Apple Inc, 2007-06-27, retrieved 2010-05-10
- ^Hertzfeld, Andy (October 1984), The Original Macintosh: Switcher, retrieved 2010-05-10
- ^Mindfire Solutions (2002-03-06), Memory Management in Mac OS(PDF), p. 2, retrieved 2010-05-10
- ^'System 7.1 upgrade guide'(PDF). Archived from the original(PDF) on 2016-03-04. Retrieved 2015-05-26.
- ^'memory maps'. Osdata.com. 2001-03-28. Retrieved 2010-05-11.
- ^Apple Computer (1991-01-01), Technical Note ME13: Memory Manager Compatibility, retrieved 2010-05-10
- ^Memory Allocation Recommendations on OS X, Apple Inc, 2005-07-12, retrieved 2009-09-22
External links[edit]
- Macintosh: ROM Size for Various Models, Apple Inc, 2000-08-23, retrieved 2009-09-22
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Classic_Mac_OS_memory_management&oldid=977422052'
When a Mac gets too full, it can slow processing times down. Your Mac can overheat. And of course, making room for anything else, whether it’s a file you need to save, a new app or game you want to download, might prove difficult. If you keep ignoring your Mac slowing down and overheating, sooner or later you are going to get a “Your disk is almost full” error.
So before that happens, now is the time to free up some much-needed storage on a Mac. In this article, we cover how to check storage space on Mac, and most importantly, how to fix the amount of space you have.
7 ways to manage storage on Mac
One of the easiest ways is to search through your files for anything that takes up too much space, then take it all to the trash. Find-and-delete is effective, to a point. But it doesn't clear everything out, as many Mac users find when they're trying to make more space.
Often, under the surface, is a lot more taking up space than you might realize. Duplicate files and folders, and photos: images can hog loads of room, especially when you’ve got duplicates or so many similar images on your Mac. Plus backups. Whenever you’ve connected an iOS device or iPod, everything at that point in time on that device is duplicated onto your Mac.
Here are some more types of junk on your computer:
Here are some more types of junk on your computer:
Great tools to manage storage on Mac
There are plenty of third-party apps to manage storage on a MacBook. CleanMyMac X gives you a whole arsenal of tools to dig out junk. On average, Mac users find they gain an extra 62GB of storage that was lost to system junk files, outdated files, and apps that they didn't need anymore.
This is the Space Lens tool in CleanMyMac X that searches for your large and unseen folders:
This is the Space Lens tool in CleanMyMac X that searches for your large and unseen folders:
Download the app here for free
Then launch it and select Space Lens at the bottom of the sidebar.
If you want to do this the manual way, here are 7 ways you can clear out more space in your Mac and manage storage more effectively.
Then launch it and select Space Lens at the bottom of the sidebar.
If you want to do this the manual way, here are 7 ways you can clear out more space in your Mac and manage storage more effectively.
#1: Empty the Trash
To start with, your Trash could be full of things that need deleting permanently. Go to the Trash icon in the bottom-right corner of the dock and click the option to Empty Trash.
However, that isn't the only trash can that a Mac has. And each one is storing anything you’ve moved in there that could be restored with a few clicks, so in effect, taking something to trash isn’t doing anything useful for the space you need to recover on your hard drive.
![App App](/uploads/1/3/4/2/134297439/724660201.gif)
macOS devices also come with trash cans as part of the iPhoto, iMovie, and Mail applications, so if you’ve deleted anything within those in the last 30 days, you will need to empty those too. Freeing up space in those apps involves pressing Ctrl+click or right-click to open and empty the Trash, thereby creating more space.
After 30 days your Mac will automatically empty out your Trash bin.
#2: Uninstall unwanted applications
Now that you’ve emptied the trash cans, one of the most noticeable sources taking up space within a Mac is apps and games that you downloaded but don't need anymore. Although there is nothing you can do about native macOS apps — the ones that come with the operating system — there is plenty you can do about apps and games that you’ve downloaded.
Open your Finder and see the list of your apps
Open your Finder and see the list of your apps
Uninstalling applications shouldn’t take too much work; except for the fact that it’s always worth checking for other folders connected to the apps and games you’re going to delete. If it looks like you've got several to uninstall, make a list so you know what to look for when checking in other locations in your Mac — such as the Library — for working folders connected to the same app.
Drag-and-drop every app you don't need to the Trash.
How to see your unused apps
Some apps don't show anywhere, even though they take up space and operate in the background. They could be intentionally hidden by the developer or be too insignificant for your Mac to display.
Luckily, there is a way to uncover all your apps, the hidden ones and the ones you never used at all. CleanMyMac X's Uninstaller tool does just that.
Here is the list of unused apps on my Mac. As you can see I, apparently, have 92 apps I never used!
Luckily, there is a way to uncover all your apps, the hidden ones and the ones you never used at all. CleanMyMac X's Uninstaller tool does just that.
Here is the list of unused apps on my Mac. As you can see I, apparently, have 92 apps I never used!
Here you can download this tool for free
After you unpack the app, click the Uninstaller tab in the sidebar
After you unpack the app, click the Uninstaller tab in the sidebar
#3: Clean up iTunes/iOS backups
If you’ve ever - or used to - physically connected your iPod, iPhone or iPad to your Mac, then there is a good chance that there is a backup of every time you've done this. Whatever was on your iOS device at the time is going to be stored within your iTunes backup files space, which can take up a whole load of room that you've probably got other uses for.
So if you want to delete these and save a whole bunch of space, close iTunes then go to the following folder within Library:
Open Finder > Go > Go to Folder..
Open Finder > Go > Go to Folder..
Type in: ~/Library/Application Support/MobileSync/Backup
Now everything stored within this backup folder can be deleted and it will save you a lot of space.
#4: Tidy temporary files
Most Mac’s accumulate a lot of temporary files and storage that isn't needed. Every so often, macOS will try and purge these, but it’s always worth doing a thorough check to make sure there isn’t anything taking up more space when you’re trying to extract every available GB. There are several places where you are going to find temporary files:
- Web browsers
- System cache files
- Application cache
Here is how to clean your temporary data in Safari (may hold up to 1 GB of space)
How to clean your Library caches:
Here you should find loads of files and folders that are taking up space you could use in better ways.
Go to Finder > Go > Go to Folder..
Now type in: ~/Library/Caches
Repat the process for:/Library/Caches Without the '~' character
Here you should find loads of files and folders that are taking up space you could use in better ways.
Go to Finder > Go > Go to Folder..
Now type in: ~/Library/Caches
Repat the process for:/Library/Caches Without the '~' character
Go inside these folders and move their content to the Trash. But don't delete these folders themselves.
Mac Storage Management App Login
If you are not sure, this app does this automatically
#5: Delete language files
Although a Mac comes with as many languages as possible, there is a good chance you only use one — maybe two or three at most — as a system preference. Scp app in mac. Deleting all of those that you are never going to use will save a lot of space.
Deleting language files should free up at least 1GB of space.
Unfortunately, there isn't an easy way to clear extra language files manually. I recommend using CleanMyMac X for this purpose because it really saves time.
Get CleanMyMac X (a link to a free edition)
Then, choose System Junk tab in the sidebar
Click Scan and the Review Details
Get CleanMyMac X (a link to a free edition)
Then, choose System Junk tab in the sidebar
Click Scan and the Review Details
#6: Clear out attachments and downloads
Whether you are using the built-in Mac Mail application, or a third-party app, or one that you login through a web browser, there is a good chance that email downloads are taking up space in your Mac. You could have years worth of downloads sitting there, waiting to be deleted, so now is your chance to clear out this junk.
Go through Downloads and drag everything into the Trash that is taking up more space than you want. You can also change settings within Mail or other email providers to avoid automatic downloads, thereby saving you even more space in the future.
#7: Check for duplicates
Define Storage Management
If your Mac, or previous versions of it had the old iPhoto app, then there is a good chance you’ve got duplicate photo libraries taking up space. You should be able to find these under Photos, where it should show you photo libraries from the new macOS Photos app and the old iPhotos app.
Mac Manage Storage System
Here is a great way to scan your Mac for duplicates — Gemini 2 app by MacPaw
Verizon message app desktop download.
Verizon message app desktop download.
Make sure everything you want to save is stored in a new folder or moved over to join other photos in your more recent storage area. Then, when you are sure everything else is an unnecessary duplicate, drag it all into the Trash. If you want to store them to make sure they don't go missing while freeing up more space on your Mac, you can always store them in the cloud (a third-party application, such as Dropbox), or through iCloud, or use an external storage device. Once you are confident everything is stored safely, delete everything you don't need and free up a whole load of space.
Final thoughts
Mac Storage Management App Software
As you can see, how to get more storage on MacBook, the manual way, can take time and effort. There are quite a few folders and files to go through, so you might be there a while trying to locate and create more space within your Mac. But it can be done. Another way is to use a powerful Mac performance tool, such as CleanMyMac X which comes with Space Lens. A quick way to see what is taking up so much space, and then using CleanMyMac X, how to recover that space.
Mac Storage Management App Download
In only a few clicks, you could have loads of new hard drive space and your Mac running as good as new. Hope you found this article helpful. Stay tuned for more Mac tips.