Operating Systems Memory-Mapped Files Access file as above is inconvenient Map files into the address space of a running process Program Program text text Data Data xyz (a (a) Segmented process before mapping files into its address space (b)Process after mapping existing file abc into one segment creating new segment for xyz Gao Haichang, Software School, Xidian University 18
Operating Systems Gao Haichang , Software School, Xidian University 18 Memory-Mapped Files (a) Segmented process before mapping files into its address space (b) Process after mapping existing file abc into one segment creating new segment for xyz Access file as above is inconvenient. Map files into the address space of a running process
Operating Systems Chapter 6: File Systems 46.1 Files H 6.2 Directories E 6.3 File system implementation H 6.4 Example file systems Gao Haichang, Software School, Xidian University 19
Operating Systems Gao Haichang , Software School, Xidian University 19 Chapter 6: File Systems 6.1 Files 6.2 Directories 6.3 File system implementation 6.4 Example file systems
Single-Level Directory Systems emh swine HRoot directory A(ABC a single level directory system H contains 4 files a owned by 3 diffe crent people, A, B, and C G Problem: different users may accidently use the same names for their files Gao Haichang, Software School, Xidian University 20
Operating Systems Gao Haichang , Software School, Xidian University 20 Single-Level Directory Systems A single level directory system contains 4 files owned by 3 different people, A, B, and C Problem: different users may accidently use the same names for their files
Operating Systems TwO-level Directory Systems User directory A C Files Letters indicate owners of the directories and files open(“x” open(“ nancy/x") Problem: it is not satisfactory for users with a large number of fil Gao Haichang, Software School, Xidian University
Operating Systems Gao Haichang , Software School, Xidian University 21 Two-level Directory Systems Letters indicate owners of the directories and files open (“x”) open (“nancy/x”) Problem: it is not satisfactory for users with a large number of files
Operating Systems C Hierarchical Directory Systems Root directory User directory. 6面回心 User subdirectories User file a hierarchical directory system(a tree of directories) Gao Haichang, Software School, Xidian University 22
Operating Systems Gao Haichang , Software School, Xidian University 22 Hierarchical Directory Systems A hierarchical directory system (a tree of directories)