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

• Case Studies