Notes

Operating system
-is an interface between application and hardware

primary function of OS
i) managing program
ii) managing memory
iii) handling input and output
iv)output user interface

four requirement for real time OS
i) multitasking
ii) process thread that can be prioritized
iii) a sufficient number of interrupt levels
iv) small embedded operating system that are packaged as part of microdevice

Mainframe OS
an operating system on mainframe computer, a powerful device mainly used by government and businesses to process a large amount of information and support a great number of user
Embedded OS
an operating system is an optional part of embedded device's system software stack. Meaning not all embedded system have one

In non pre-emptive scheduling, a process is remain in running state until it explicitly performs an action that will move to waiting scheduling queue
In pre-emptive scheduling, a running process also move to waiting scheduling queue by external acts occurring outside the running process

Round Robin
-designed especially for time-sharing system

Short job first
- an non pre-emptive discipline which waiting job with smallest estimated run-time-to-completion is run next

First-Come-First-Served
-process is dispatched according to their arrival time on ready state. Being the non pre-emptive discipline. Once a process has a CPU, it will runs to completion

Other Name for FCFS
i) First-In-First-Out
ii) Run-To-Completion

Device Driver
translate IO function call which specific hardware device I/O request

Deadlock
permanent blocking of a set of process which either compete for system resources or communicate with each other

plug and play is an ability of computer to detect and configure a new piece of hardware automatically

starvation
a situation in which some client cannot access a service, while other can

PCB information
-a pointer to locate memory of processes
-a register save are
-a priority of process
-A processor it is running on
-unique identification of process in order to track 'which is which' information
-a pointer to parent process
-similarly, a pointer to child process(if exist)

5 state
new- a process is created
ready- the process is ready to execution
running- the process is in execution
terminate/halted- the process is completed execution
waiting- the process is in wait state for input or output operation

deadlock avoidance
-the process may exit while holding resources
-there must be a fixed number of resources to allocate

reusable process
-used by a process at a time and not depleted by that use

why process suspended?
swapping
-the operating system need to release sufficient main memory to bring it in a process that is ready to execute

other os reason
-the operating system may suspended background process

timing
-the process may be executed periodically

different between foreground process and background process
-Foreground process has higher priority over background process

condition of deadlock
-mutual exclusion- at least one unshareable resource
-hold and wait - process hold one resource while waiting for another
-no preemption- process only release voluntanly, no interruption possible
-circular wait- circular chain process, each waiting for resource held by another