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Unix foundations
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| bet | 5/9 | | Sana | 19.05.2023 | | Hajmi | 1.51 Mb. | | #61987 |
Bog'liq processI/O Tables - I/O device is available or assigned
- Status of I/O operation
- Location in main memory being used as the source or destination of the I/O transfer
File Tables - Existence of files
- Location on secondary memory
- Current Status
- Attributes
- Sometimes this information is maintained by a file-management system
Process Table - Process image consists of program, data, stack, and attributes
- Attributes
Process Control Block Process Identification - Unique numeric identifier
- may be an index into the primary process table
- User identifier
- who is responsible for the job
- Nonprocess Kernel
- Execution Within User Processes
- operating system software within context of a user process
- process executes in privileged mode when executing operating system code
Execution of the Operating System - Process-Based Operating System
- major kernel functions are separate processes
- a process is invoked by the operating system
- A special program that runs directly on the hardware.
- Implements the process model and services.
- Resides on disk, in a file /vmunix or /unix.
- Bootstrapping: loads the kernel.
- Initializes the system and sets up the environment, remains in memory before shut down
UNIX Services - System call interface
- Hardware exceptions
- Divide by 0, overflowing user stack
- Interrupts
- Swapper, pagedaemon
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