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, operatingsystem, 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 userprograms, 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 sharedmemory for the exchanged of information between processes
error detection - correct errors to ensure a consistentstate
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: WindowsOS
Multiprocessing OS
Has more than one independent processing unit, example: Unix
Batch OS
Only does one thing at a time, example: bank statement