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98 lines
2.8 KiB
Markdown
98 lines
2.8 KiB
Markdown
---
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title: "13-OS-intro"
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aliases:
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tags:
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- cosc204
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- lecture
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sr-due: 2022-10-30
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sr-interval: 8
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sr-ease: 230
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---
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# why learn OS
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- security
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- optimisation
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- wierd bugs
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- "crown of programming"
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- understand hardware better
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- embedded sys and IoT
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- co-design of hardware and software
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# what is an OS
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- a program (also called OS kernel) loaded onto RAM first when pc is turned on
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- OS kernel (in kernel space) has highest privilege and can access any hardware directly
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- user programs (in user space) cannot acces hardware unless permitted otherwise by the OS kernel via service request (sys call)
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> a program (OS kernel) that manages the different aspects of the opereration of the machine and runs with the highest privilege in a protected domain
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manages:
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- processes
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- data storage
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- ram, file systems
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- io devices
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- network
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- ui
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- security and protection
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## kernel vs user space
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- cpu can check space of software via flag in status word
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- when interrupt or sys call occurs, the flag is ser to kernel space
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- kernel
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- protected space where software can access hardware
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- OS kernel is run in kernel space
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- user
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- other software is run in user space
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- non privilege space where softwar cannot access hardware
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- unless permitted by kernel
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## process management
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a process is a program in execution
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- a program is not a process
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process management involves
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- creating and deleting processes
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- scheduling processes
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- suspending and resuming processes
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- process synchronisation
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- process communication
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- deadlock handling
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## storage manangement
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storage:
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- primary (RAM)
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- secondary (hard drive)
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- tertiary (floppy disks, tapes, cd, etc)
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storage manangement involves:
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- Allocating and deallocating storage
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- Keeping track of storage in use and free storage
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- Transferring data between primary and secondary storage
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Defn: the file system is the mechanism by which the user accesses/manipulates sotred data in secndary storage like hard disk
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## io device managment
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- A computer system can include a very wide range of I/O devices: keyboards, mice, printers, hard disks, CD-roms, etc etc etc.
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I/O device management includes tasks like:
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- tracking the status of each device
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- allocating devices to particular processes
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- deallocating devices
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- scheduling tasks for individual devices (e.g. disk scheduling)
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- these functions are built into modules called device drivers; each device needs one device driver to manage the hardware and serve the requests from user applications via the OS kernel.
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### UI
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Defn: the shell is the program through which the user interactins with the operating system
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two types:
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- icon based point and click
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- keyboard commands e.g., UNIX
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- harder to learn but more powerful and flexible
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# history
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- No OS
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- batch systems
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- spooling
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- time sharing
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- real time
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