Mac Memory Manacement
Computers and Technology
Submitted By TripleD
Mac Memory Management
For rough draft
Mac OS is available on two processor architectures: the Motorola 68k series and the PowerPC.
Mac OS has a flat address space, shared between all processes. There is no per-process memory protection. Application code runs in supervisor mode, so there is no instruction protection. Mac OS has virtual memory, in the limited sense that a larger fixed address space can be simulated, by storing the entire address space on disc. This size of this address space is fixed at boot time.
The lowest part of memory is occupied by the system partition. This contains some system global values which applications should not access directly, although there is nothing to prevent them doing so.
Historically, the 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 OS X.
The original problem for the engineers of the Macintosh was how to make optimum use of the 128 KB of RAM that the machine was equipped with. Since at that time the machine could only run one application program at a time, and there was no fixed secondary storage, the engineers implemented a simple scheme which worked well with those particular constraints. However, that design choice did not scale well with the development of the machine, creating various difficulties for both programmers and users.
References: The Memory Management Reference Memory management in Mac OS, en.wikipedia.org Mac OS memory management
Mac Process Management
For rough draft
The Process Manager manages the scheduling of processes.
The number of processes is limited only by available memory. The Process Manager maintains information about each process— for example, the current state of the process, the address and size of its partition, its type, its creator, a copy of all process-specific system global variables, information about its 'SIZE' resource, and a process serial number. This process information is referred to as the context of a process.
The Process Manager assigns a process serial number to identify each process. A process serial number identifies a particular instance of an application; this number is unique during a single boot of the local machine. The foreground process has first priority for accessing the CPU. Other processes can access the CPU only when the foreground process yields time to them. There is only one foreground process at any one time. However, multiple processes can exist in the background.
Mac OS, you're used to having a clock in the menu bar, and having the option to turn it on or off and perhaps set the font. This functionality is a built-in part of the OS and user interface. With Unix, if you want a clock, you run a separate program that displays a clock. Because the clock is a program and not an integral part of the OS, it can be any program. By selecting different programs, the clock can be made to appear as any type that you choose, anywhere on the screen that you choose.
References: Mac OS X Unleashed By John Ray and William C. Ray,
Process Manager in Macintosh Operating System, Mindfire Solutions
Mac File Management For rough draft
OS X’s basic tools for finding and managing files—the Finder and Spotlight—are fine. But savvy users find ways to make them better. For some, that means making the Finder work better, with smart folders and meticulous filing systems. For others, that means turning to some third-party utilities that let them manage files their way.
In the Finder, users set up a bunch of smart folders that keep track of related files. Some of the handiest smart folders collect Microsoft Word files with Mac 911 in the title (File Name Contains Mac 911, Kind Is Other Microsoft Word); BBEdit files containing blog as a keyword (Kind Is Other BBEdit, Keywords Contains blog); and files larger than 1GB, which users periodically review to see whether any can be archived or thrown away to free up disk space (Size Is Greater Than 1 GB). Users keep these and other smart folders in the Finder sidebar; they also plant key ones in their Drag Thing Frequently Used palette.
Some people dump all their files into one folder and then use Spotlight to find the files they need. But for some, Spotlight is too slow and unreliable to use for regular file finding; it’s also of little help when users want to find a document on another networked Mac. Users still find it most useful to keep their documents organized meticulously into folders. They have several general ones (Finances, Macworld, and so on) in their user folder’s /Documents folder. Inside each of those folders are folders for each year. Inside each of those folders are folders for specific products and articles—200905 iPhone Tricks, for example, and 20090310 Mac mini Review. Users also include dates in my document names. Compulsive? Perhaps.
References: MacWorld, Manage files in OS X your way
For rough draft
Security to the general Macintosh user has never been much of an issue. Turn it on, use it, turn it off when you’re done. And even if you’ve got a DSL or other dedicated line, warnings related to hack attempts on open and dedicated networks lines never seemed to instill fear in a Mac user. Sure there are products like Norton Personal Firewall or NetBarrier 2.0, but these are for professionals’ right? Well, not really. But the truth is, for the general Macintosh user, the chances of getting hacked are pretty low. Especially if that user does not frequent any on-line chat facilities or make any on-line purchases or things of that nature. The main reason for this lack of concern comes from the same idea that keeps Macs safe from most computer viruses. Most personal computer users (about 85%) use Windows or some other WinTel based operating system. For this reason, few hackers even know anything about Mac OS and the remaining minority really doesn’t seem to care. This keeps Macintosh users safe to a large degree from most any random hack attempt.
The most effective way to ensure that your Mac OS X system stays secure for months and years to come is to leave the root account alone. In current builds of Mac OS X, Apple has disabled root access to the system. Sure it can be hacked and then used for a login account however this is not recommended for the average user. Apple has designed the OS to allow a system administrator (user account created at install or given these rights by the original admin) to accomplish most tasks without needing to use the root account. Because the root account is the absolute power in a UNIX-based OS, this account can cause heavy damage to the system if it should happen to crash while logged in as root or can open up back doors simply by changing privileges on the system.
References: SecureMac, Macintosh OS X Security Understanding the Platform and Usage
Mac OS Comparisons Between Windows and UNIX/Linux
For rough draft
Apple's Macintosh OS is even older than Windows. It is the first ever successful graphical-based operating system, being released one year before its Microsoft counterpart.
Pros: 1. Viruses: Apple Macs get almost no viruses. This is mostly due to Window's superior market share. 2. Reliability: Macs only run on Apple computers, and are thus less prone to hardware and software crashing. 3. Looks: Let's face it, most of the time; Mac just looks better than Windows.
1. Expensive: Mac costs even more than Windows. 2. Only available on Apple computers: If you already have a computer, you cannot install MAC on it unless it's an Apple. Otherwise, you must buy a new computer. 3. Compatibility: Only a few programs will run on Mac, and almost no games.
Mac OS X is built on Darwin, an open source OS by Apple – Darwin is again based on another open source OS, Free BSD. Undoubtedly, Apple is the King when making user interface. It has all the eye-candy without sacrificing stability and performance. While it is true that you can almost mimic every aspect of Mac OS in Linux, there is a problem – stability. All those are experimental packages and might crash X-Window. Unlike Windows or Linux, Mac OS X is supposed to be installed only in Mac machines. Most users think the stability of the operating system has a major role in this decision. They already know all about their hardware and how to make the most out of it.
* Excellent user interface and usability * Stable & Secure – It is not necessarily more stable than Linux, Linux is also stable if you don’t install any experimental package. But most users have to agree that, with all the eye-candy Mac OS X is stable as any Linux distro – this cannot be true with Linux. Users have to decide between eye-candy interface or stable OS, not both – well, at least until this time. Regarding security, it is considered as one of the best – but some tests conducted on Mac reveals that it is also vulnerable to attacks but it is less targeted by hackers (only below 5% of people use mac). * Applications – A large number of excellent professional applications are available in this platform and hence preferred by designers and other professionals. * Easy installation of applications * Targeted less by viruses & spywares
* Though, based on open source operating systems, it is still proprietary. * The Operating system is limited to a specific platform * Cost of ownership is high – User is not free to try it out by paying for the operating system alone, instead the user is forced to buy new hardware at premium prices.
If compared purely on performance and stability, Mac OS has an upper hand. Also unlike Linux, there is lot of commercial software available, which makes it the choice of professionals. But can we say Mac OS X is the best? Certainly not. First of all, as said above, Mac OS X is not like Windows or Linux. It is created for a particular hardware and won’t work with other hardware. Just think about Linux, it supports almost all hardware platforms – be it Intel, AMD or anything, Linux works just fine. If Linux was targeted for a particular architecture, it would’ve been more stable than Mac. Secondly, the high cost of ownership – it doesn’t give you choices, it will force you to buy something that it supports with a premium price.
References: Informatics-Tech, Linux vs Macintosh vs Windows (unbiased comparison), & Techno Mania, Windows, Linux and Mac – A comparison