The document discusses the components and system calls of the Windows operating system. It describes the main layers as the hardware abstraction layer, kernel, and executive which run in kernel mode. User-mode subsystems include environmental and protection subsystems. The main system call types are process control, file manipulation, device manipulation, information maintenance, and communications. Process control calls include creating and terminating processes while file manipulation calls involve opening, reading and writing files.

1. Unit -1
SYSTEM COMPONENTS AND SYSTEM CALLS IN OPERATING SYSTEM
BY RAM K PALIWAL
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2. System Components
The architecture of Windows Operating System is a layered
system of modules.
◦ The main layers are the HAL, the kernel, and the executive, all of
which run in kernel mode, and a collection of subsystems and
services that run in user mode.
◦ The user-mode subsystems fall into two categories:
◦ the environmental subsystems, which emulate different operating systems.
◦ protection subsystems, which provide security functions.
◦ One of the chief advantages of this type of architecture is that
interactions between modules are kept simple. The remainder of
this section describes these layers and subsystems.
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4. System Components
Main Components are
◦ Hardware Abstraction Layer
◦ Kernel
◦ Executive Section
Hardware abstraction Layer
The HAL is the layer of software that hides hardware chipset differences from
upper levels of the operating system. The HAL exports a virtual hardware
interface that is used by the
◦ kernel dispatcher
◦ The executive,
◦ the device drivers.
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5. System Components
Kernel
The kernel layer of Windows has four main responsibilities:
◦ thread scheduling
◦ low-level processor synchronization
◦ interrupt and exception handling
◦ switching between user mode and kernel mode
Executive
The Windows executive provides a set of services that all environmental
subsystems use. The services are grouped as follows:
◦ object manager
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6. System Components
◦ virtual memory manager
◦ process manager
◦ advanced local procedure call facility
◦ I/O manager
◦ cache manager
◦ security reference monitor
◦ plug-and-play and power managers
◦ Registry
◦ booting.
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7. System Calls
System calls provide an interface to the services made available by
an operating system.
These calls are generally available as routines written in C and C++,
although certain low-level tasks (for example, tasks where hardware
must be accessed directly) may have to be written using assembly-
language instructions.
Before we discuss how an operating system makes system calls
available, let’s first use an example to illustrate how system calls are
used: writing a simple program to read data from one file and copy
them to another file.
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9. System Calls
Types of System Calls
1. Process control
2. File manipulation
3. Device manipulation
4. Information maintenance
5. Communications
6. Protection.
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10. System Calls
Process control
◦ end, abort
◦ load, execute
◦ create process, terminate process
◦ get process attributes, set process attributes
◦ wait for time
◦ wait event, signal event
◦ allocate and free memory
Protection
◦ Get permission, set permission
◦ Allow user, deny user
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11. System Calls
File management
◦ create file, delete file
◦ open, close
◦ read, write, reposition
◦ get file attributes, set file attributes
Device management
◦ request device, release device
◦ read, write, reposition
◦ get device attributes, set device attributes
◦ logically attach or detach devices
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12. System Calls
Information maintenance
◦ get time or date, set time or date
◦ get system data, set system data
◦ get process, file, or device attributes
◦ set process, file, or device attributes
Communications
◦ create, delete communication connection
◦ send, receive messages
◦ transfer status information
◦ attach or detach remote devices
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13. References
1. Operating System Concept ninth Edition by Abraham Silberschatz and Galvin
2. https://electricalfundablog.com/operating-system-os-functions-types-resource-management/
3. http://ecomputernotes.com/fundamental/disk-operating-system/types-of-operating-system
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