4.1. Identifying File-Naming Conventions

File-naming conventions have undergone several changes over the years. In this section, you get a look at where they have been and where they are now. You also take a look at the differences between filenames and directory entries.

When MS-DOS was the premier OS on the market, it set the standard of the eight-dot-three (8.3)–character filename. This file system was created by using 32 character fields (bytes) for the filenames. If you work out the math, you're probably wondering where the extra characters are. Well, 8 plus 3 is 11, and that leaves 21 outstanding characters (bytes). Table 4-1 summarizes how each byte is used.


The File Allocation Table (FAT) is an index on your file system that holds a pointer to where each file is stored on your hard drive. On an NTFS (NT file system), this is called the Master File Table (MFT). To move a file on a file system, you only need to change its reference in the table, and not its location in the file system.

Table 4.1. Directory Entry Format
Filename8 bytes
Extension3 bytes
Attribute1 byte
Reserved10 bytes FAT 32 uses two of these bytes.
Time2 bytes
Date2 bytes
First cluster2 bytes
Size4 bytes

With every system or component used in a computer, there is a limit; sometimes it is a very large limit, but a limit, nonetheless. That limit is always based on a binary number. Computer systems have ...

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