operating system concept

• system programs - manage the operations of a computer
• multitasking systems - run more than one process at a time
• single-user systems - support one user at a time
• computer systems consist of - main(user, application programs, operating system, hardware), optional(network, data, procedure)
• sub process - light weight process, break down complex task into smaller part
• OS(operating system) - a layer of software that manages and interface all parts of hardware, shields programmers from hardware complexity
• OS can be defined as - a resource collector, resource manager, a control program, act as an intermediary of computer user and computer hardware
• OS runs in kernel or supervisor mode to protect user from tampering with hardware
• OS is regarding as one of the programs that running all time and also called as kernel
• systems calls are used for communication between OS and application program
• an initial program runs also called bootstrap program
• boot up computer start with: POST -> BIOS -> MBR -> GRUB -> kernel -> systemd -> targets
• BIOS(basic input output system) - serves as a intermediary of OS and computer hardware
• basic functions of OS - accept command from user, provides desired service for user and user programs, system manager, manages computer resources effectively
• services provided by OS - program execution, input-output operations, file system manipulation, communication, error detection
• program execution - loads program in memory, runs the executions either normally or abnormally
• input-output operations - control input output devices
• file system manipulation - allow reading, writing, deletion and creating of files
• communication - manage shared memory for the exchanged of information between processes
• error detection - correct errors to ensure a consistent state
• Services to ensure efficient operations in OS - resource allocation, accounting, protection
• resource allocation - decide the best method to utilize the CPU
• accounting - calculate performance, cost, resources to ensure efficient operation
• protection - protect user process and data
• Classification of Operating Systems

  • Multitasking OS
  • Time Sharing OS
  • RTOS (Real Time OS)
  • Multiprogramming OS
  • Multiprocessing OS
  • Batch OS
  • Single-user OS
  • Multi-user OS
• Multitasking OS

  Allows simultaneous execution of programs with single processor, example: Microsoft Windows, Linux
• Time Sharing OS

  Allows multiple simultaneous users, programs are executed bit by bit, example: Unix
• RTOS (Real Time OS)

  Designed to respond within a certain period, example: weapon system, robots
• Multiprogramming OS

  Allows more than one active user program stored in memory simultaneously, example: Windows OS
• Multiprocessing OS

  Has more than one independent processing unit, example: Unix
• Batch OS

  Only does one thing at a time, example: bank statement
• Single-user OS

  Allows one user at a time to use computer
• Multi-user OS

  Allows more than one user to use computer