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| OS and System software |
Operating system
An operating system is an organized collection of software
that controls the overall operations of a computer. In other words,
operating system is a program that acts as an interface between
the user of a computer and computer hardware.
Purposes of an operating system:
The purposes of an operating system are as follows:
- It optimizes the computer user’s intervention in and concern about machine’s internal workings.
- It provides an environment in which a user may execute programs.
- It controls and coordinates the use of hardware among the various application programs.
Computer System & List the components of computer system:
A computer system consist of hardware, system software, application programs and the users.
The components of computer system are:
i) Hardware(CPU,memory,I/O devices)
ii) System Software(Operating system)
iii) Application programs(compilers, DBMS,Editor, Spreedsheets)
iv) The Users.
System Software and its classification.
System software refers to programs that are tools to assists the computer user to generate application programs, debug and test them ,modify them and finally execute them.
Tasks of supervisor program:
The operating system control program is commonly called the supervisor. The supervisor handles the overall management of a computer system. It is maintained in memory and it supervises the loading of other parts of the operating system from secondary storage into main memory as they are needed. It also supervises the loading the application programs for execution. The supervisor also interprets and it keeps track of jobs.
The operation of the command interpreter.
The portion of operating that can accept, interpret and carry out user commands are referred to as the command interpreter. The command interpreter consist of a number of individual programs modules, each responsible for handling a single command.
Individual user commands to COPY a file. FORMET a disk and so on, are handled by command interpreter. Commands to the operating system of a microcomputer are actually request to execute individual command interpreter programs.
Serial Batch processing and multiprogramming
What do you understand by serial batch processing?
System batch operating systems can run only a single user program at a time.
These are simple system systems generally used on mainframes that run in batch mode and on single user microcomputers.
List some advantages of serial batch systems.
i) It allows a computer to dedicated to a specific use.
ii) It is less complex.
iii) There is only one user at a time.
iv) There is no possibility that multiple program will deadlock.
Disadvantages of serial batch processing systems:
i) A long turnaround time is needed.
ii) Batch systems are slow in both processing and output.
iii) In batch system the programs must be debugged statically.
List some of the disadvantages of the multiprogramming systems.
i) It is fairly sophisticated and more complex than serial batch operating system.
ii) A multiprogramming operating systems must keep track of all the jobs it is concurrently running.
Time sharing and Multiprocessing Operating systems.
Difference between time sharing and multiprogramming systems:
The primary difference between time sharing and multiprogramming operating systems is the criterion that is applied for switching between jobs. Multiprogramming systems are described as being event driven, and time sharing systems are time driven. In other words, a multiprogramming system switch from one program to another on the basis of some event(such as I/O request). A time sharing system, on the other hand, switches to different job when the clock says to.
Pipeline processing:
In pipeline systems, multiple processors are used to perform different stages of consecutive computer instructions simultaneously. The processors are arranged like a factory production line, allowing several operands to be in different stages of execution at the same time.
Segmentation:
Segmentation is the process of dividing up a program that is to be run into a number of chunks (or segments) of different sizes and placing these segments in memory wherever they fit. Segmentation divides programs into pieces of different sizes, which are stored in secondary storage and transferred into primary memory.
Paging:
Paging is similar to segmentation except that programs are divided into equal sized portions. As with segmentation, the operating system keeps track of page locations by constructing page table. As pages are fixed sizes, the use of pages can result in less waste of real storage space.
Types of operating systems:
i) Process controls systems.
ii) Process monitor systems.
Function and evaluation of operating systems.
List of the function of a modern operating system.
i) Provides for human-computer interaction.
ii) Boots or starts the computer operations.
iii) Schedules job.
iv) Manage data file storage.
v) Assigns different task to the CPU.
vi) Provides security and control.
Tasks of information management:
i) Managing groups of file.
ii) Managing file directories.
iii) Processing and managing the records within a file.
Computer and operating system structure.
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| operating system structure |
Four classes of interrupts:
Four general classes of interrupts are:
i) Program, trap instructions, page faults etc.
ii) Timer.
iii) I/O devices.
iv) Hardware failure.
Interrupt and the causes of occurring interrupts:
A method by which other events can cause an interruption of the CPU’s normal execution. An Interrupt is a method by which the normal operation of the CPU can be changed. Interrupts are a better solution than polling for handling I/O devices.
The functions of device independent software:
The functions of device independent software are below:
i) Device naming.
ii) Device protection.
iii) Buffering.
iv) Providing a device independent block size.
v) Error reporting.
vi) Allocating and releasing dedicated devices.
vii) Uniform interfacing for the device drivers.
List some examples of device controllers.
Examples of device controllers are below:
I/O Controllers I/O Address
Keyboard 060-063
Printer 320-32F
Floppy disk 3F0-3F7
Memory mapped I/O:
Each controller has a few registers that are used for communicating with the CPU and these registers are part of the regular memory address space. This is called memory mapped I/O.
I/O devices:
Normally all input and output operations in operating system are done through two types of devices; block oriented devices and character oriented devices.
Block oriented device: A block oriented device is one in which information is stored and transferred at some fixed block size (usually some multiple of 512 bytes), each one with its own address. The block oriented device can read and write each block independently of all other ones out or espand.
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kitty