Error detection ensure correct computing by detecting

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• Error detection – ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs.
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SUSHMA RAWAL 30 Additional Operating System Functions Additional functions exist not for helping the user, but rather for ensuring efficient system operations. – Resource allocation – allocating resources to multiple users or multiple jobs running at the same time. – Accounting – keep track of and record which users use how much and what kinds of computer resources for account billing or for accumulating usage statistics. – Protection – ensuring that all access to system resources is controlled.
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SUSHMA RAWAL 31 System Calls • System calls provide the interface between a running program and the operating system. – Generally available as assembly-language instructions. – Languages defined to replace assembly language for systems programming allow system calls to be made directly (e.g., C, C++) • Three general methods are used to pass parameters between a running program and the operating system. – Pass parameters in registers . – Store the parameters in a table in memory, and the table address is passed as a parameter in a register. Push (store) the parameters onto the stack by the program, and pop off the stack by operating system.
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SUSHMA RAWAL 32 Passing of Parameters As A Table
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SUSHMA RAWAL 33 Types of System Calls • Process control • File management • Device management • Information maintenance • Communications
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SUSHMA RAWAL 34 System Programs • System programs provide a convenient environment for program development and execution. The can be divided into: – File manipulation – Status information – File modification – Programming language support – Program loading and execution – Communications – Application programs • Most users’ view of the operation system is defined by system programs, not the actual system calls.
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SUSHMA RAWAL 35 UNIX System Structure • UNIX – limited by hardware functionality, the original UNIX operating system had limited structuring. The UNIX OS consists of two separable parts. – Systems programs – The kernel • 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.
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SUSHMA RAWAL 36 UNIX System Structure
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SUSHMA RAWAL 37 Layered Approach • The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface. • With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers.
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SUSHMA RAWAL 38 An Operating System Layer
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SUSHMA RAWAL 39 Microkernel System Structure • Moves as much from the kernel into “ user ” space. • Communication takes place between user modules using message passing. • Benefits: - easier to extend a microkernel - easier to port the operating system to new architectures - more reliable (less code is running in kernel mode) - more secure
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Error detection ensure correct computing by detecting...

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