CSMC 412Operating SystemsProf. Ashok K Agrawala© 2006 Ashok AgrawalaSet 21CMSC412 Set 2September 06CMSC412 Set 2The Evolution of Operating SystemsSeptember 06 23Topics• History of Operating Systems• Tasks of an Operating System• OS as extension of the hardware• Main concepts: processes, files, system calls• Operating system structuringSeptember 06 CMSC412 Set 24Operating Systems Concepts• System software manages resources• OS hides complexity of underlying hardware• Layered architecturesPhysical devicesMicroprogrammingMachine languageOperating systemCompilers EditorsCommand interpreterBanking systemAirline reservationWeb browserApplication programsHardwareSystem programsSeptember 06 CMSC412 Set 25History of operating systems• Batch processing• Punching cardsMultiprocessing programmingThe elements of the basic The elements of the basic IBM 1401 system are the IBM 1401 system are the 1401 Processing Unit, 1401 Processing Unit, 1402 Card Read1402 Card Read--Punch, Punch, and 1403 Printer. and 1403 Printer. Job 3Job 2Job 1OSMemory partitionsSeptember 06 CMSC412 Set 26The Evolution of Operating System Functionality• Batch Job Processing– Linkage of library routines to programs – Management of files, I/O devices, secondary storage• Multiprogramming– Resource managment and sharing for multiple programs – Quasi-simultaneous program execution– Single user • Multiuser/Timesharing Systems– Management of multiple simultaneous users interconnected via terminals– Fair resource management: CPU scheduling, spooling, mutual exclusion• Real-Time Systems (process control systems)– Management of time-critical processes– High requirements with respect to reliability and availabilitySeptember 06 CMSC412 Set 27Tasks of an Operating System• Processor management - Scheduling – Fairness – Non-blocking behavior– Priorities• Memory management– Virtual versus physical memory, memory hierarchy– Protection of competing/conurrent programs• Storage management – File system – Access to external storage media• Device management– Hiding of hardware dependencies– Management of concurrent accesses • Batch processing– Definition of an execution order; throughput maximizationSeptember 06 CMSC412 Set 28Kernel- and User Mode ProgramsTypical functionality implemented in either mode:Kernel: • Privileged mode• Strict assumptions about reliability/security of code• Memory resident– CPU-, memory-, Input/Output managment– Multiprocessor management, diagnosis, test – Parts of file system and of the networking interfaceUser Space: • More flexible• Simpler maintenance and debugging– Compiler, assembler, interpreter, linker/loader– File system management, telecommunication, network management– Editors, spreadsheets, user applicationsSeptember 06 CMSC412 Set 29Layered Model of Operating System Conceptsnr name typical objects typical operations1 Integrated circuits register, gate, bus Nand, Nor, Exor2 Machine language instruction counter, ALU Add, Move, Load, Store 3 Subroutine linkage procedure block Stack Call, JSR, RTS 4 Interrupts interrupt handlers Bus error, Reset 5 Simple processes process, semaphore wait, ready, execute 6 Local memory data block, I/O channel read, write, open, close 7 Virtual model page, frame read, write, swap 8 Process communication channel (pipe), message read, write, open 9 File management files read, write, open, copy 10 Device management ext.memory, terminals read, write 11 I/O data streams data streams open, close, read, write 12 User processes user processes login, logout, fork 13 Directory management internal tables create, delete, modify 14 Graphical user interface window, menu, icon OS system callsSeptember 06 CMSC412 Set 210OS acts as Extension of Hardware• System view: layered model of OS – Implementation details on one layer are hidden from higher layers• Same machine, different operating systems:– IBM PC: DOS, Linux, NeXTSTEP, Windows, SCO Unix – DEC VAX: VMS, Ultrix-32, 4.3 BSD UNIX • Same OS, different machines: UNIX – PC (XENIX 286, APPLE A/UX) – CRAY-Y/MP (UNICOS - AT&T Sys V) – IBM 360/370 (Amdahl UNIX UTS/580, IBM UNIX AIX/ESA) • Windows NT, XP, 2000, 2003– Intel i386 (i486 an NT 4.0), Alpha, PowerPC, MIPS, ItaniumSeptember 06 CMSC412 Set 211Operating Systems Evolution5560657075808590950003IOCSDOS/360DOS/VDSEVSVS/ESAOS/360MVS/370MVS/XAMVS/ESTSOIBSYSCTSSCP/CM5VM/370VM/XAVM/ESASYSTEM IIISYSTEM VSYSTEM V.4MULTICSUNIXUNIXV.7AIX/370AIXSUN OSPOSIXSOLARIS 24.1BSD4.2BSD4.3BSD4.4BSDMACHOSF/1AIX/ESAXENIXMS-DOS 1.0CP/MDR/DOSOS/2WIN 3.0WIN NTWIN 2000WIN 9XWIN XPLINUXRSX-11MVMS 1.0VMS 5.4VMS 7.3WIN 3.1SOLARIS 10RT-11LINUX 2.6WIN Server 2003September 06 CMSC412 Set 212Main Concepts: processes• Processes, process table, core image• Command interpreter, shell• Child processes• Scheduling, signals• User identification, group identificationready runningblockedfinishednewAB CFEDProcess treeSeptember 06 CMSC412 Set 213Main Concepts: Files• Files, directories, root• Path, working directory• Protection, rwx bits• File descriptor, handle• Special files, I/O devices• Block I/O, character I/O• Standard input/output/error• pipesRoot directorytmp usretcpitmiaSeptember 06 CMSC412 Set 214Main concepts: system calls• User programs access operating system services via system calls • Parameter transmission via trap, register, stackcount=read(file, buffer, nbytes);• 5 general classes of system calls:– Process control– File manipulation– Device manipulation– Information maintenance– communicationsSeptember 06 CMSC412 Set 215Main concepts: shell• Command interpreter• Displays prompt, implements input/output redirection• Background processes, job control, pseudo terminals$ date$ date >file$ sort <file1 >file2$ cat file1 file2 file3 > /dev/lp1$ make all >log 2>&1 &September 06 CMSC412 Set 216Structuring of Operating Systems• Monolithical systems• Unstructured• Supervisor call changesfrom user mode intokernel modeApp AppSystem servicesHardwareOS proceduresUser ModeKernel ModeSeptember 06 CMSC412 Set 217Layered OS• Each layer is given access only to lower-level interfacesApplicationProgramApplicationProgramApplicationProgramSystem ServicesFile System Memory and I/O Device Management Processor SchedulingHardwareUser ModeKernel ModeSeptember 06 CMSC412 Set 218Microkernel OS(Client/server OS)Kernel implements:• Scheduling• Memory
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