UNIX V7 file system was used in PDP-11 minicomputers. Files are placed in a tree structure having a root directory. New items which are added to the root directory in the tree are known as links. Here, file names can be at a maximum of 14 characters. ASCII characters can be used in the file name except the forward slash (/) since it is used as a separator in path names.
UNIX V7 directory entry: Here are the components of a UNIX V7 directory entry:
1) I-node number: It is used to represent the number of I-nodes for a file. It has a size of 2 bytes. I-nodes has attributes including file size, information about creation, last access, and last modification of file, group, protection information, owner, and count of number of directory entries that point to i-node. Whenever a link is added, count is increased by 1 and whenever a link is removed, count is decreased by 1.
2) File name: It represents the file name. It has a size of 14 bytes.