Here are some other formats: CP/M: extent map made up of directory entries. The file size is in units of sectors, but text files end with ^Z. Ctrl-M Ctrl-J i

Here are some other formats: CP/M: extent map made up of directory entries. The file size is in units of sectors, but text files end with ^Z. Ctrl-M Ctrl-J is end of line. TRSDOS (TRS-80), also used extents. This whole extent concept came from DOS/360 from IBM mainframes. Apple DOS: directory entry points to a linked-list of indirection sectors which hold pointers to the sectors that make up the file. The size of a file is in units of sectors, except that for text files, the end of the file is indicated with NUL. Ctrl-M is end of line. Atari DOS: just like the C64- a linked list of sectors, but with 3 bytes of overhead per 128 byte sector (the extra byte contains the number of valid data bytes in the sector). The file size is in units of bytes due to this. End of line for text files is 0x9b. (ESC with 7th bit set). MS-DOS: files are made of a linked-list of clusters, but the linked list for all the files are stored in one place- the FAT (nicely eliminating the need for a free-space bitmap). But if you overwrite the FAT, you lose everything! Early version of UNIX (SCO Xenix) didn't use a bitmap for the free blocks, instead it kept them a linked list. This was a really bad idea, files instantly became fragmented.