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Operating Systems

Resources

  • https://github.com/o-oconnell/minixfromscratch

Rough History

  • so computing machines were developed and
  • earlier computing machines use punch cards as the programs
  • then transistors came around and things were small and them machines needed an operating system which will help to run the program and manage the machine
  • so there were many types of operating systems
    • batch os - so when one program finish execution another one is loaded
    • real time
  • after this unix came around with its small kernel and able to run on multiple types of system

Terms in OS

https://www.youtube.com/watch?v=xW5fgPMbRz4

single tasking and multi tasking OS

  • single tasking run one program at a time
  • multi tasking run more than one program concurrently
    • this is achieved by time sharing
    • preemptive multitasking
      • forces process to give time

single user and multi user OS

  • no facilities to distinguish users
    • may allow multiple programs to run in tandem
  • multi user
    • extends multi-tasking with facilities to identify processes and resources belonging to multiple users

distributed OS

  • manages a network of distinct networked computers

embedded OS

  • used in embedded devices

real time OS

  • guarantees to process events or data by specified moment in time

library OS

  • one in which services that a typical os provided are given in form of libraries

time sharing OS

  • sharing computer resource among multiple users at the same time by means of multiprogramming and multi-tasking

multiprogramming OS

  • this term means that when when we run some process
  • now the process will need access to any peripherals
  • so it will wait for the access and this is slow and waste time
  • so we can put another process in cpu that time
  • this is multiprogramming

batch processing

  • running jobs in batches automatically

preemptive

  • temporarily interrupting a process forcefully

non-preemptive

  • when the process interrupts itself

Processes, Threads

  • So process is a program in memory, which is loaded with the help of operating system.

  • so when a process is created then the operating system adds a pcb to it

  • pcb - process control block - in a multi tasking operating system

    • data structure used by computer operating systems to store all the information about a process
    • process identification - process id
    • process state - new, ready, running, waiting, dead
    • process control
    • program counter - the address to the next instruction
  • thread

    • is the smallest sequence of programmed instructions
    • that can be managed independently by scheduler
    • which is typically part of os
  • multiple threads of a process can be executed concurrently using multi threading

    • sharing resources such as memory while different process do not share these resources

Resources