The first file system used in Mac OS file system of the Macintosh (MFS), which was only possible to use a level folder provides. This system file in the next version, with file system (HFS) file system hierarchical) that has a tree structure file management. was replaced. In conjunction with the file system of Mac operating system should be an important point noted that it was from file systems other operating systems are distinct. Most file systems that is DOS, Unix, or other operating systems use. simply file as a series of bytes, contiguous in the fall, with each file requires a program that are recognize which file contains what information. Contrary to this rule, the MFS and HFS file as two separate sections (section data and resources section) in the fall. Section data (the Data) contains information similar to other operating systems (for example, the data portion of the can contains the text of a document or information is a video file). The section resources(Resource) contains other information structurally related to the file (such as definitions of menus, graphics, sound, or codes administration). A file may only include the resources sector to be (in the data it is empty), or include only part of data is while the resources sector it is empty), or contains both the data and resources. A text file can be text in the data portion of the file and information related to the type of format and formatting text in the resource file, save. This order to be done when, for example, if a program with the format of the text formatting was not familiar, at least to be able to read your text. From the other side, the segmentation causes disharmony and lack of compatibility with other operating systems; copying a file from the file system of Mac System File, non of the Mac Resources section, the file goes. In Mac OS X from the structure of the memory management and multi-processing control, the same operating system, Unix, is used. This operating system is based on the core Mach (Mach kernel) is a small core operating system, which at the University of Carnegie Mellon in the states TV Us during a research project about parallel computing and distributed is created and the version of the BSD operating system Unix is an operating system by Steve Jobs at the company NeXT created and developed. Memory management system the new implementation of the program, the more you are on time and closing other apps running to cause the crash of a program can help prevent. Also, the operating system, the second operating system, the Macintosh is where the command line is also included. however, that to use this command line must Terminal Emulator by the user, run the Mac OS, the command line was not the first Mac operating system that has a command line. OS, A/UX is that its development has been suspended). Problems caused by several is that Mac OS X compared to Mac OS less user-friendly, and is working with it more difficult. Including these factors requires hardware more powerful to run the operating system. failure to provide some functionality of the operating system that a previous version existed, and some incompatibility serious with the previous version (because the drivers written for the Mac OS compatible with Mac OS X are not).