Computer Science (Paper-I)
1. Operating System
Operating system:-
An Operating system is a system program which acts as an interface
between the user of computer and the computer hardware.
An operating system is a program or software which manages all the
computer hardware.
It provides the base for application program and acts as an
intermediary between a user and the computer hardware.
Computer system components are divided into 4 parts:-
- Computer hardware
- Operating system
- Application programs
- User
Functions of operating system:-
1. The primary aim of the operating system is to make the
hardware convenient to use.
2. Operating system helps to user to execute program.
3. Operating system controls execution of program to prevent
errors and improper use of computer system.
4. Operating system makes provision for security of information
to users.
5. Operating system eliminates duplicate errors by number of
programmers in development of complicated routines.
6. Operating system provides facility to shares the same
hardware among the users.
7. Operating system schedules resources (h/w) among users.
8. Operating system used to keep tracks of free sectors for
allocation of new files.
Services in Operating System:-
1. Information Management:-
Information Management manages all the information within the
system. It provides the facility to store, retrieve, modify or remove the
information on files/directories. These system services manage the
organization of information into files and directories by allocating
memory space to them.
, System services or system calls of IM:-
- Create a file.
- Create a directory.
- Open a file for read/write purposes.
- Explore a directory.
- Close a file.
- Read data from file to buffer.
- Write data from buffer to file.
- Move file pointer.
- Create a link.
- Change working directory.
2. Process Management:-
Process Management manages the various processes under execution
in the system. In multiuser OS, a number of users may execute same
or different programs at a time. But such a computer system has only
one CPU and it can execute only one instruction, belonging to any one
of these programs at one time.PM of such OS keeps track of all
running programs called processes, schedule them and dispatch them
one after the other. While doing so, it gives an impression to each user
that it has the full control of CPU.
System services or system calls of PM:-
- Create child process identical to parent.
- Wait for child process to terminate
- Read a process.
- Block a process
- Resume a process
- Terminate a process
- Suspend a process
- Delay a process
- Change the priority of a process
- Dispatch a process
- Generate a process
3. Memory Management:-
Memory management manages the main memory. It Keep tracks of
various files or process. The OS keeps a list of all free memory
locations. Before a program is loaded in memory, the MM consults
with this list. It loads the program into memory and modifies the list.
When the program is executed completely, it removes the program
from main memory and again modifies the list.For this, the OS
determines memory allocation/deallocation policies and user various
techniques and algorithms to achieve this.
System services or system calls of MM:-
- To allocate a chunk of memory to a process.
- To free chunk of memory from a process.
, System call:-
A system call is a mechanism that provides the interface between a
process and the operating system. It is a programmatic method in
which a computer program requests a service from the kernel of the
OS.
System call offers the services of the operating system to the user
programs via API (Application Programming Interface). System calls
are the only entry points for the kernel system.
Working of System Call:-
Here are the steps for System Call in OS:
Step 1) The processes executed in the user mode till the time a
system call interrupts it.
Step 2) After that, the system call is executed in the kernel-mode on a
priority basis.
Step 3) Once system call execution is over, control returns to the user
mode.
Step 4) The execution of user processes resumed in Kernel mode.
Need of System Calls in OS:-
Following are situations which need system calls in OS:
- Reading and writing from files demand system calls.
- If a file system wants to create or delete files, system calls are
required.
- System calls are used for the creation and management of new
processes.
- Network connections need system calls for sending and receiving
packets.
- Access to hardware devices like scanner, printer, need a system
call.
Windows 98 OS:-
Features of Windows 98 OS:-
1. Easier to use:-
Windows 98 is a single user multitasking operating system.
Navigating around the computer is easier in windows 98. A file can be
opened by a single click. Windows 98 allows us to use multiple
monitors with single computer. New hardware can be easily installed
and used without restarting computer. With windows 98 we can use
digital cameras and other digital imaging devices.
2. Faster:-
Windows and programs open faster than in Windows 95.
The computer speed and efficiency can be easily improved by simple
maintenance.
3. True web integration:-
Windows 98 can be easily connected to internet. Web pages can be
viewed in any window. Using Microsoft Outlook Express, Emails and
1. Operating System
Operating system:-
An Operating system is a system program which acts as an interface
between the user of computer and the computer hardware.
An operating system is a program or software which manages all the
computer hardware.
It provides the base for application program and acts as an
intermediary between a user and the computer hardware.
Computer system components are divided into 4 parts:-
- Computer hardware
- Operating system
- Application programs
- User
Functions of operating system:-
1. The primary aim of the operating system is to make the
hardware convenient to use.
2. Operating system helps to user to execute program.
3. Operating system controls execution of program to prevent
errors and improper use of computer system.
4. Operating system makes provision for security of information
to users.
5. Operating system eliminates duplicate errors by number of
programmers in development of complicated routines.
6. Operating system provides facility to shares the same
hardware among the users.
7. Operating system schedules resources (h/w) among users.
8. Operating system used to keep tracks of free sectors for
allocation of new files.
Services in Operating System:-
1. Information Management:-
Information Management manages all the information within the
system. It provides the facility to store, retrieve, modify or remove the
information on files/directories. These system services manage the
organization of information into files and directories by allocating
memory space to them.
, System services or system calls of IM:-
- Create a file.
- Create a directory.
- Open a file for read/write purposes.
- Explore a directory.
- Close a file.
- Read data from file to buffer.
- Write data from buffer to file.
- Move file pointer.
- Create a link.
- Change working directory.
2. Process Management:-
Process Management manages the various processes under execution
in the system. In multiuser OS, a number of users may execute same
or different programs at a time. But such a computer system has only
one CPU and it can execute only one instruction, belonging to any one
of these programs at one time.PM of such OS keeps track of all
running programs called processes, schedule them and dispatch them
one after the other. While doing so, it gives an impression to each user
that it has the full control of CPU.
System services or system calls of PM:-
- Create child process identical to parent.
- Wait for child process to terminate
- Read a process.
- Block a process
- Resume a process
- Terminate a process
- Suspend a process
- Delay a process
- Change the priority of a process
- Dispatch a process
- Generate a process
3. Memory Management:-
Memory management manages the main memory. It Keep tracks of
various files or process. The OS keeps a list of all free memory
locations. Before a program is loaded in memory, the MM consults
with this list. It loads the program into memory and modifies the list.
When the program is executed completely, it removes the program
from main memory and again modifies the list.For this, the OS
determines memory allocation/deallocation policies and user various
techniques and algorithms to achieve this.
System services or system calls of MM:-
- To allocate a chunk of memory to a process.
- To free chunk of memory from a process.
, System call:-
A system call is a mechanism that provides the interface between a
process and the operating system. It is a programmatic method in
which a computer program requests a service from the kernel of the
OS.
System call offers the services of the operating system to the user
programs via API (Application Programming Interface). System calls
are the only entry points for the kernel system.
Working of System Call:-
Here are the steps for System Call in OS:
Step 1) The processes executed in the user mode till the time a
system call interrupts it.
Step 2) After that, the system call is executed in the kernel-mode on a
priority basis.
Step 3) Once system call execution is over, control returns to the user
mode.
Step 4) The execution of user processes resumed in Kernel mode.
Need of System Calls in OS:-
Following are situations which need system calls in OS:
- Reading and writing from files demand system calls.
- If a file system wants to create or delete files, system calls are
required.
- System calls are used for the creation and management of new
processes.
- Network connections need system calls for sending and receiving
packets.
- Access to hardware devices like scanner, printer, need a system
call.
Windows 98 OS:-
Features of Windows 98 OS:-
1. Easier to use:-
Windows 98 is a single user multitasking operating system.
Navigating around the computer is easier in windows 98. A file can be
opened by a single click. Windows 98 allows us to use multiple
monitors with single computer. New hardware can be easily installed
and used without restarting computer. With windows 98 we can use
digital cameras and other digital imaging devices.
2. Faster:-
Windows and programs open faster than in Windows 95.
The computer speed and efficiency can be easily improved by simple
maintenance.
3. True web integration:-
Windows 98 can be easily connected to internet. Web pages can be
viewed in any window. Using Microsoft Outlook Express, Emails and
