File System History

In 1981, IBM introduced its first personal computer, which ran a new operating system designed by Microsoft, MS-DOS. The computer contained a 16-bit 8088 processor chip and two drives for low-density floppy disks. The MS-DOS file system, FAT (named for its file allocation table), provided more than enough power to format these small disk volumes and to manage hierarchical directory structures and files. The FAT file system continued to meet the needs of personal computer users even as hardware and software power increased year after year. However, file searches and data retrieval took significantly longer on large hard disks than on the original low-density floppy disks of the first IBM personal computer.

By the end of the 1980s, the prediction of "a computer on every desk and in every home" was less a dream and more a reality. Personal computers now had 16-bit processors and hard disks of 40 MB and more — so big that users had to partition their disks into two or more volumes because the file allocation table's limit was 32 MB per volume. (Later versions of MS-DOS allowed for larger disk volumes.)

In 1990, a high-performance file system (HPFS) was introduced as a part of the OS/2 operating system version 1.x. This file system was designed specifically for large hard disks on 16-bit processor computers. On the heels of HPFS came HPFS386. It was introduced as part of Microsoft LAN Manager and was designed to take advantage of the 32-bit 80386 processor chip.

Today's personal computers include a variety of very fast processor chips and can accommodate multiple, huge hard disks. The new Windows NT file system, NTFS, is designed for optimal performance on these computers.

Because of features such as speed and universality, FAT or HPFS are now popular and widely used file systems. NTFS offers consistency with these two file systems, plus advanced functionality needed by corporations interested in greater flexibility and in data security.

Before discussing how each file system organizes data on the disk, the next section briefly reviews how a disk is organized.