Introduction of operating system, operating system functions, Brief history of operating system, types of operating system, how operating system works? DOS, TOS
☪☪☪☪☪☪☪☪☪☪☪☪☪☪☪⚝⚝⚝⚝
💬 Introduction of operating system:-
An operating system is an essential component of a computer system. The primary objectives of an operating system is to make computer system convenient to use and utilise computer hardware in an efficient manner.
An operating system is a large collection of software which manages resources of the computer system, such as memory, processor, file system and input/output devices. It keep track of the status of each resources and decides who will have a control over computer resources, for how long and when.
👉User.
👉 Application program.
👉 system program.
👉 Operating system.
👉 computer hardware.
Components of computer system,
We can say that operating system is a program that link's between a user of a computer and the computer hardware.
Operating system execute user program and make solving user program easier.
☪ Operating system manages different resources (CPU, memory, disk,etc).
disk,
Memory
✦ Operating system improves performance ( response time, throughput, etc).
✦ Operating system allows portability enables easier programming (no need to know details of the underlying hardware.)
✦ Operating system interface between the hardware and rest of the machine....editors,
compilers, user programs etc.
✦ Operating system allows resources to be used in an efficient manner.
✧✦ Operating system provides the platform for execution of user programs.
✦ Operating system allows efficient usage; parallel activity, avoids wasted cycles.
✦ Operating system provided information protection.
✦ Operating system given each user a slice of the resources.
✦ Operating system acts as a control program.
👉Types of Operating system:-
There are generally four types of operating system, categorized based on the types of computers. These categorizes are:
1. Real-Time Operating system (RTOS):- Real Time Operating system are used to control machinery, scientific instruments and industrial system. A very important part of an in precisely the same amount of time, every time it occurs. An RTOS typically has very little user-interface capability, and no user utilities, since the system will be a sealed box" when delivered for use.
2. Single- User, single Task (SU, ST):- This operating system is designed to manage the computer so that one user can effectively do one thing at a time. The palm OS for palm handheld computers is a good example of a modern single-user, single-task is called operating system.
3. Single-User, Multi-Tasking (SU, MT):- This operating system is used by most people on their desktop and laptop computers today. Microsoft's Windows and Apple's MacOS platforms are both examples of operating systems that will let a single user have several programs on operation at the same time. For example, it's entirely possible for a windows user to write a note in a word processor which downloading a file from the internet.
4. Multi-User (MU):- This operating system allows many different users to take advantage of the computer's resources simultaneously. The operating system must make sure that the requirements of the various users are balanced, and that each of the programs they are using has sufficient and separate resources so that a problem with one user doesn't affect the entire community of user. Examples of multi-user operating system are Unix, VMS and mainframe operating system such as MVS.
👉How Operating System Works?
When you turn on the power of a computer the first program that runs is usually a set of instruction kept in the computer's read-only memory (ROM). This program examines the system hardware to make sure everything is functioning properly. Generally this program is called power-on-self test (POST). POST check the CPU, Memory, and basic input-output system (BIOS) for errors and store the result in a special memory location. Once the POST has successfully completed, the software loaded in ROM ( Sometimes called the BIOS or firmware) will begin to activate the compute's disk drives.
👉 Bootstrap Loader:-
Set up the divisions of memory that hold the operating system, user information and applications. it establishes the data structures that will hold the myriad signals, flags and semaphores that are used to communication within and between the subsystems and applications of the computer. After this, it turns control of computer over to the operating system.
👉 Why is Booting Required?
💬 Hardware doesn't know where the operating system resides and how to load it.
💬 Need a special program to do this job- Bootstrap loaded.
💬 E.g. BIOS- Boot input output system.
💬 Bootstrap loader locates the kernel, loads it into main memory and starts its execution.
💬 In some systems, a simple bootstrap loader fetches a more complex boot program from disk, which in turn loads the kernel.
👉How Boot Process Occurs:-
✦ Reset event on CPU ( power up, reboot) causes instruction register to be loaded with a predefined memory location. It contains a jump instruction that transfers execution to the location of Bootstrap program.
✦ This program is form of ROM, since RAM is in unknown state at system startup. ROM is convenient as it needs no initialization and can't be affected by virus.
👉Boot Step's:-
✦ Run diagnostics to determine the state of machine. If diagnostics pass, booting continues.
✦ Runs a power-on self test (POST) to check the devices that the computer will rely on, are functioning.
✦ BIOS goes through a preconfigured list of devices until it finds one that is bootable. if it finds no such devices, an error is given and the boot process stops.
✦ Initializes CPU register, device controllers and contents of the main memory. After this, it loads the OS.
✦ On finding a bootable device, the BIOS loads and executes its boot sector. in the case of a hard drive, this is referred to as the master boot record (MBR) and is often not OS specific.
✦ The MBR code checks the partition table for an active partition. If one is found, the MBR code loads that partition's boot sector and executes it.
✦ The boot sector is often operating system specific, however in most operating systems its main function is to load and execute a kernel, which continues startup.
Secondary Boot:-
✦ If there is no active partition or the active partition's boot sector is invalid, the MBR may load a secondary boot loader and pass control to it and this secondary boot loader will select a partition (often via user input) and load its boot sector.
✦ Examples of secondary boot loaders.
■ GRUB-GR and unified Bootloader
■ LILO-LInux Loader
■ NTLDR- NT loader
👉 Disk Operating System (DOS):-
✦ After identifying the location of boor files, BIOS looks at first sector (512 bytes) and copies information to specific location in RAM (7C00H)- Boot Record.
✦ Control passes from BIOS to a program residing in the boot record.
✦ Boot record loads the initial system file into RAM. for DOS, it is IO.SYS.
✦ The initial file, IO.SYS includes a file called SYSTEM which loads the remaining OS into the RAM.
✦ SYSINIT loads a system file MSDOS.SYS that knows how to work with BIOS.
✦ Another special file that is loaded is one which tells what specific application or commands user wants to be performed as part of booting process. In DOS, it is Autoexec.BAT. In Windows, its WIN. INI.
👉 Tasks of Operating System.
Generally the tasks of the operating system can be categorised into the following five categories:
💬 Processor Management.
💬 Memory Management.
💬 Device Management.
💬 Distributed System.
💬 Protection and security.
Comments