Executable files, for example, are binary files in the special format required by the operating system. Executable
files are process images ready to be brought in from the disk, stored in memory, and executed.
UNIX takes the unique approach that any file is just a stream of bytes. If there??™s any structure to the
information in the file, it??™s up to the application program to create the structure, and later to interpret it. In some
applications this shifts some responsibility away from the file system manager to the application, but it is
a simple, consistent conception.
File System Units
The file system relies on the disk hardware, of course. Disks almost always transfer multiples of a 512-byte
sector. Even if your program tries to read a street address that is no more than 25 characters long, the disk will
actually return to the operating system at least one sector, and somewhere within will be the street address. The
sector is the unit of storage for the disk hardware.
Usually the file system has a larger unit of storage than the sector. This minimum storage allocation for
a file is called a block or cluster. Even a file consisting of a single character will require one cluster of space on
the disk.
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