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Memory ManagementTo execute a program all (or part) of the instructions must be in memoryAll (or part) of the data that is needed by the program must be in memoryMemory management determines what is in memory and whenOptimizing CPU utilization and computer response to usersMemory management activitiesKeeping track of which parts of memory are currently being used and by whomDeciding which processes (or parts thereof) and data to move into and out of memoryAllocating and deallocating memory space as needed
File-system ManagementOS provides uniform, logical view of information storageAbstracts physical properties to logical storage unit -fileEach medium is controlled by device (i.e., disk drive, tape drive)•Varying properties include access speed, capacity, data-transfer rate, access method (sequential or random)File-System managementFiles usually organized into directoriesAccess control on most systems to determine who can access whatOS activities include•Creating and deleting files and directories•Primitives to manipulate files and directories•Mapping files onto secondary storage•Backup files onto stable (non-volatile) storage media
Mass-Storage ManagementUsually disks used to store data that does not fit in main memory or data that must be kept for a “long”period of timeProper management is of central importanceEntire speed of computer operation hinges on disk subsystem and its algorithmsOS activitiesMounting and unmountingFree-space managementStorage allocationDisk schedulingPartitioningProtectionSome storage need not be fastTertiary storage includes optical storage, magnetic tapeStill must be managed – by OS or applications
Storage management: Data viewdir21:file21.1 file21.2 file21.3dir22:file22.1 file22.2 file22.3dir23:file23.1 file23.2 file23.301010101011010010101101011010110101101001010101011101011010110101File system basedview – content visibleas files and directories USERFILE SYSTEMDISK SYSTEMBlock based viewcontent considered asblocks of dataPhysical view –all data just a streamof bits
UNIX UNIX – limited by hardware functionality, the original UNIX operating system had limited structuring. Systems programsKernel•Consists of everything below the system-call interface and above the physical hardware•Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one level
What are possible OS architectures?How do we build an OS that has all the above functions?UNIX like – monolithic – throw everything into one pile and call it layered!Something more structured..