lecture1.pdf
- 1. Dr. Ihab Sbeity Info 212 Operating System I Dr. Ihab Sbeity Lebanese University – Faculty of Sciences I 2011-2012
- 2. Physical parts of a computer Hardware Info 212 - UL - Dr. Ihab Sbeity
- 3. Basic Hardware Elements Basic Hardware Elements Processor - traditionally controls the operation of the computer and performs the data processing function Memory - Stores data and programs, typically volatile (aka real or primary memory) Info 212 - UL - Dr. Ihab Sbeity volatile (aka real or primary memory) I/O modules - move data between computer and external environment (i.e. disks, network) System Bus - communication among processors, memory, and I/O modules
- 4. Computer-System Architecture Info 212 - UL - Dr. Ihab Sbeity
- 5. Processors A processor is hardware that executes machine-language CPU executes the instructions of a program Coprocessor executes special-purpose instructions Ex., graphics or audio coprocessors Registers are high-speed memory located on processors Info 212 - UL - Dr. Ihab Sbeity Registers are high-speed memory located on processors Data must be in registers before a processor can operate on it Instruction length is the size of a machine-language instruction Some processors support multiple instruction lengths
- 6. Processors Info 212 - UL - Dr. Ihab Sbeity
- 7. Clocks Computer time is measured in cycles One complete oscillation of an electrical signal Provided by system clock generator Processor speeds are measured in GHz (billions of cycles per second) per second) Modern desktops execute at hundreds of megahertz or several GHz Info 212 - UL - Dr. Ihab Sbeity
- 8. Memory The memory hierarchy is a scheme for categorizing memory Fastest and most expensive at the top, slowest and least expensive at the bottom Registers L1 Cache L2 Cache Main Memory Secondary and tertiary storage (CDs, DVDs and floppy disks) Main memory is the lowest data referenced directly by processor Volatile – loses its contents when the system loses power
- 9. Memory Info 212 - UL - Dr. Ihab Sbeity
- 10. Main Memory Main memory consists of volatile random access memory (RAM) Processes can access data locations in any order Common forms of RAM include: dynamic RAM (DRAM) – requires refresh circuit dynamic RAM (DRAM) – requires refresh circuit static RAM (SRAM) – does not require refresh circuit Info 212 - UL - Dr. Ihab Sbeity
- 11. Buses A bus is a collection of traces Traces are thin electrical connections that transport information between hardware devices A port is a bus that connects exactly two devices An I/O channel is a bus shared by several devices to perform An I/O channel is a bus shared by several devices to perform I/O operations Handle I/O independently of the system’s main processors Info 212 - UL - Dr. Ihab Sbeity
- 12. System Software Info 212 - UL - Dr. Ihab Sbeity
- 13. Operating system (OS) Definition « the set of all programs allowing the user of the computer system to make the best use of the machine’s resources in a coherent and comfortable way » Interface between the computer system users and the physical machine Physical parts Machine language Kernel command Interpreter, compiler, applications (games, office tools, …) MACHINE OPERATING SYSTEM APPLICATIONS Info 212 - UL - Dr. Ihab Sbeity
- 14. Operating system (OS) Represents the interface users/machine: Masks the hardware details from applications The OS must handle these details Controls the applications execution By controlling periodically the CPU Informs the CPU when to execute the programs It must optimize the resources use to maximize the system performance Info 212 - UL - Dr. Ihab Sbeity
- 15. Abstract view of the OS components Info 212 - UL - Dr. Ihab Sbeity
- 16. The Kernel Insures Different types of services management of the processor(s) Loading and launching programs Memory management (primary secondary) Input/output management (peripherals) Info 212 - UL - Dr. Ihab Sbeity
- 17. The principal OS (1/2) Solaris/Linux Built on Unix kernel The best compromise : reliable, efficient, portable, evolutive difficult to use for beginners Linux distributions Red Hat Fedora S.u.S.e S.u.S.e Debian Mandrake.. MacOS Less and less used because ofWindows Very good ergonomically, reliable, stable Has developed its own standards (even for the hardware)… has lost the concurrence againstWindows (unless some advantages like digital photo) Info 212 - UL - Dr. Ihab Sbeity
- 18. The principal OS (2/2) Windows The most known, user oriented (automatic configuration always available), many kinds of tools (some are now standards), simplest manipulation. Less reliable even if some progress is done since Win2000/XP,/Vista/7; bad security (virus, very few intrusions) Win2000/XP,/Vista/7; bad security (virus, very few intrusions) Less open, imposes most of the technological choices and restricts the users in these choices. Other systems reserved to big servers VMS, GCOS, MVS and AS400 … Info 212 - UL - Dr. Ihab Sbeity
- 19. History of OSs – first generation Use Mode The user writes the program in machine language It reserves the machine for a fixed duration The user then loads manually the program in memory The machine executes The machine executes If the execution doesn’t match the user’s needs è Step by step execution eventual modification New trial until complete satisfaction or time out Use mode totally inefficient Info 212 - UL - Dr. Ihab Sbeity
- 20. Perforated cards One line of data or program was coded by holes that could be read by the machine Info 212 - UL - Dr. Ihab Sbeity
- 21. Operator reading a set of perforated cards Info 212 - UL - Dr. Ihab Sbeity
- 22. History of OSs –second generation Batch systems Better hardware transistors printed circuits Appearance diversity of peripherals perforated card readers printers magnetic devices (bandes, cards, …) Info 212 - UL - Dr. Ihab Sbeity
- 23. Batch systems – How do work? The first OS (late-50s) The user submits a job to an operator Program then data The operator loads a set of jobs on the reading device A program, the monitor (OS), manages the execution of each job A program, the monitor (OS), manages the execution of each job of the set the monitor is always in memory and ready to execute the users (compiler) of the monitor are loaded on need Only one program in memory, programs are executed in sequence The output is normally on a file, printer, magnetic band… Info 212 - UL - Dr. Ihab Sbeity
- 24. 3rd generation : Multiprogramming batch I/O operations are extremely slow (compared to other instructions) ex. a loop in a program may take abort 10 microseconds, while a disk operation takes abort 10 milliseconds It’s the difference between an hour and a month and a half! even with a little bit of I/O, a program spends the majority of the time waiting even with a little bit of I/O, a program spends the majority of the time waiting So: poor CPU use when a program is in memory Info 212 - UL - Dr. Ihab Sbeity
- 25. How does it work? Multiprogramming Many activities progress in parallel – an activity holds the CPU until the next O/S – manipulating the O/S operation ends by interruptions
- 26. Interruptions To be able to execute other jobs when a job waits for an I/O Memory protection : isolate the jobs Hardware management many jobs are ready to be executed asking for ressources: Requirements for multiprogramming many jobs are ready to be executed asking for ressources: CPU, memory, I/O devices Language for managing jobs execution : interface between users and OS before JCL (Job Control Language), now shell,command prompt and others. Info 212 - UL - Dr. Ihab Sbeity
- 27. Advantages and disadvantages Advantages Good management of ressources (CPU, memory, peripherales) Good response time for short jobs Disadvantages Complexity of the hardware and the operating system Sharing and protection of ressoruces Info 212 - UL - Dr. Ihab Sbeity