Understanding the Causes of Problems

The causes of the problems you experience will be one?or a combination?of five general types of problems:

  • User error

  • Bugs

  • Conflicting software

  • Attacks on your system

  • Hardware failures

Each of these problems is detailed in the sections that follow.

User Error

The results of many investigations into aviation accidents can often be summed up with the phrase "pilot error." Similarly, this is often the case with an "accident" in the Mac world. Many problems are the direct result of a user (this means you) doing something improperly?or not doing something properly. Some of the things you might do to cause problems for yourself are the following:

  • Not following instructions? This is the big one. Many times, you will cause your own problems simply because you fail to follow the instructions provided with software or hardware. You should become a believer in the old adage "if all else fails, follow the instructions."

  • Operating a machine past its limits? If you know that a particular application requires a computer with a G4 processor, but you try to run it on a G3-equipped Mac, you are bound to have troubles. If you live on the edge of your machine's capabilities, you will have more problems than you might with a more capable machine.

  • Not doing proper maintenance on your system? If you don't keep an eye out for patches and updates to Mac OS X as well as the applications you use, you might experience more problems than you have to. Take advantage of the many ways in which you can keep your system up-to-date. For example, Mac OS X's Software Update feature can help you keep your system and all your Apple applications current.

  • Not keeping enough free space on a drive? This is a fairly common cause of problems. All drives need to have free space to be capable of storing files, sometimes temporarily. If a drive is full, or very close to being full, you will have problems as you try to store more data on it. This can be an even bigger problem under Mac OS X because virtual memory is always on?low disk space can cause problems related to insufficient RAM as well.


Sometimes the cause of a problem is a bug inherent in the design of the products involved. The bug can be a design flaw, a manufacturing problem, or a conflict with some other part of your system. Although companies often do the best they can to prevent bugs, there is usually no way to prevent all the possible bugs in a product. Many bugs aren't revealed until a piece of software or hardware is combined with some other pieces of hardware or software.

Conflicting Software

One of the most common causes of problems is conflicting software. Some programs just don't play well with others. Conflicts are often associated with system-level applications and resources because they modify the low-level operations of the system. However, applications can also conflict with one another and cause you headaches.

Because Mac OS X features protected memory, these types of conflicts are much less common under Mac OS X than they were under previous versions of the Mac OS. Because of protected memory, you aren't likely to experience any conflicts between applications. However, there is still the potential for conflict between software that modifies the system and the core OS.

Attacks on Your System

The two primary sources of attacks on your system come from the outside: viruses and hackers. Viruses can cause all sorts of problems from simple and silly messages appearing to strange dialog boxes to major system crashes and even data deletions or hard disk failures. However, viruses that do serious damage have traditionally been fairly rare on the Mac, but because Mac OS X is based on Unix, it remains to be seen whether viruses will be a more significant source of concern than they have been for Mac users. Fortunately, viruses are among the easier problems to avoid. On the other hand, if you use a broadband connection to the Internet, your Mac will be subjected to all sorts of hackers who want to do damage to you or others. These are definitely the more serious of the two possible sources of attacks.


Although attacks are normally associated with someone from outside your local network, this is not always the case. Sometimes, even unknowingly (such as in an email-based virus attack), users on your local network can wreak havoc on your system. The proper use of user accounts and permissions and a bit of paying attention will go a long way toward preventing incursions on your Mac from a local user.

To learn how to defend yourself against these attacks, see "Defending Your Mac from Net Attacks," p. 908.

Hardware Failures

The most unlikely cause of problems is a hardware failure. Although hardware does fail now and again, it doesn't happen very often. Hardware failures are most likely to occur immediately after you start using a new piece of hardware or close to the end of its useful life. Sometimes, you can induce a hardware failure when you upgrade a machine or perform some other type of maintenance on it?for example, if you install new RAM in a machine but fail to seat a RAM chip properly.

The most common problems associated with hardware devices are actually related to the device drivers that enable the OS to communicate with the device.

    Part I: Mac OS X: Exploring the Core
    Part III: Mac OS X: Living the Digital Life