Device-status table: contains entry for each I/O device indicating its type, address, and state.System call: request to the operating system to allow user to wait for I/O completion.OS determines which type of interrupt has occurred by polling or the vectored interrupt system.Trap is a software generated interrupt caused by error or user request.Incoming interrupts are disabled while another interrupt is being processed.Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines.Device controllers inform CPU that it is finished w/ operation by causing an interrupt. ![]() ![]() Stored in ROM or EPROM (known as firmware), Initializes all aspects of system, loads OS kernel and starts execution.Bootstrap program: loaded at power-up or reboot.Kernel: the one program running at all times on the computer.Control program: controls execution of programs to prevent errors and improper use of computer.Resource allocator: decides between conflicting requests for efficient and fair resource use.Computer system: Hardware ↔ OS ↔ Applications ↔ Users (↔ = 'uses').system easy to use, utilize hardware efficiently Goals: Execute user programs, make the comp. ![]()
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