Introduction

What Operating Systems Do

• A computer system can be divided into: hardware, operating system, application programs, users
• An operating system performs no useful function by itself, but provides an environment within which other programs can do useful work.

  Computer-system Organization

• Bootstrap program in ROM
• interrupt vector is an array of pointers to interrupt routines.
• I/O and storage

  Computer-system Architechture

• Multicore systems are multiprocessor, not all multiprocessor are multicore
• Blade servers : each processor boots independently and runs its own OS.
• Clustered System: Individual systems are joined via LAN to provide high availability (service will continue even one fails)

  Operating-system Structure

• Multiprogramming: Run multiple programs to increase the utilization of the CPU.
• Time Sharing: is a logical extension of multiprogramming that CPU executes multiple jobs by switching fast.
• To ensure reasonable response time, use swapping or virtual memory.

  Operating-system Operations

• A trap is a software-generated interrupt caused either by an error or request
• Use a mode bit to indicate in user mode or kernel mode to avoid user programs to crash OS.
• A Timer is used to detect possible infinite loops in user programs.

  Process Management

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