OOperating Systems Capabilities: Multiprogramming. Multitas king TRADITIONAL SINGLE- MULTIPROGRAMMING PROGRAM SYSTEM ENVIRONMENT PROGRAM 1 PROGRAM 2 PROGRAM 1 9zu z PROGRAM 3 UNUSED MEMORY UNUSED MEMORY
HUANG Lihua, Fudan University Operating Systems Capabilities: Multiprogramming, Multitasking OPERATING SYSTEM UNUSED MEMORY PROGRAM 1 TRADITIONAL SINGLEPROGRAM SYSTEM OPERATING SYSTEM UNUSED MEMORY PROGRAM 1 PROGRAM 2 PROGRAM 3 MULTIPROGRAMMING ENVIRONMENT
crating Systems Capabilities Virtual storage Virtual Storage is the method of handling several programs in primary storage Program divided into Fixed length portions(pages) OR Variable length(segments) Current portions reside in primary storage, portions swapped out when done
HUANG Lihua, Fudan University Operating Systems Capabilities: Virtual Storage • Virtual Storage is the method of handling several programs in primary storage: – Program divided into • Fixed length portions(pages) OR • Variable length (segments) – Current portions reside in primary storage, portions swapped out when done
erating Systems Capabilities: time sharing MANY USERS SHARE LARGE CPU Time in CPu divided into slices(e.g: 2 microseconds) Each user has access to cpu during slice Single CPU is fast, can do much during time slice Users job swapped out at end of slice
HUANG Lihua, Fudan University Operating Systems Capabilities: time sharing MANY USERS SHARE LARGE CPU: • Time in CPU divided into slices (e.g.: 2 microseconds) • Each user has access to CPU during slice. • Single CPU is fast, can do much during time slice • User’s job swapped out at end of slice
crating Systems Capabilities Multiprocessing Links together two or more CPUs to work in parallel in a single computer systems to execute two or more instructions Program can be divided to be processed by multiple cPus Can process large programs more rapidly
HUANG Lihua, Fudan University Operating Systems Capabilities: Multiprocessing • Links together two or more CPUs to work in parallel in a single computer systems to execute two or more instructions. – Program can be divided to be processed by multiple CPUs. – Can process large programs more rapidly *
(operating Systems Capabilities File Systems Reality: Disks are sets of tracks(磁道) Tracks are sets of sectors(扇区) Sectors can store fixed- sized byte blocks illusion: Disks are sets of directories(目录) Directories contain other directories or files Files are variable- size byte sequences Directories and files have names
HUANG Lihua, Fudan University Operating Systems Capabilities: File Systems • Reality: – Disks are sets of tracks(磁道） – Tracks are sets of sectors（扇区） – Sectors can store fixed- sized byte blocks • Illusion: – Disks are sets of directories （目录） – Directories contain other directories or files – Files are variable- size byte sequences – Directories and files have names