Types of System Calls

Types of System Calls

Overview of System Call Categories

• The lecture introduces the concept of system calls and outlines that they can be categorized into five major types.

• The five categories are: Process Control, File Manipulation, Device Management, Information Maintenance, and Communications.

Process Control

• Process control involves system calls used to manage processes, including starting, stopping, and handling errors in process execution.

• Key functions include normal termination (End) when a process completes successfully and abnormal termination (Abort) when an error occurs.

• Additional examples include:

• Load: To load a process into memory.

• Execute: To run the loaded process.

• Create/Terminate Process: For initiating or ending a process.

• Attributes of processes can be managed with system calls like Get/Set Process Attributes, while waiting for execution time is handled by Wait for Time.

• Memory management during execution includes Allocate and Free Memory to ensure efficient resource use.

File Manipulation

• This category encompasses system calls for managing files, such as creating, deleting, opening, closing, reading from, writing to files.

• Examples include:

• Create File: To create new files.

• Delete File: To remove existing files.

• Open/Close: For accessing or releasing file resources.

• The practical application was illustrated through copying data from an input file to an output file using various system calls like Read and Write.

Device Management

• Device manipulation refers to managing input/output devices through specific system calls designed for device access and control.

• Important functions include:

• Request Device: A call made by a process needing access to a device.

• Release Device: A call made after the device is no longer needed by the process.

• Other operations involve reading/writing data from/to devices and getting/setting device attributes.

Understanding System Calls

Types of System Calls

• Physical vs. Logical Attachment: Physical attachment refers to manually connecting a device to the system, while logical attachment means the operating system recognizes and prepares the device for use. Logical detachment involves removing the device from the system's recognition without physically unplugging it.

• Example of Logical Detachment: An example is using a pen drive; right-clicking on its icon to eject or safely remove hardware demonstrates logical detachment, where the device appears removed from the system even though it's still physically connected.

Device Manipulation System Calls

• Device Management Overview: All system calls related to managing devices fall under device manipulation. This includes operations that allow interaction with various hardware components.

Information Maintenance System Calls

• Definition and Importance: Information maintenance involves keeping all relevant data about the system updated, such as date and time. These calls ensure that essential information remains accurate.

• Examples of Information Maintenance Calls:

• get time or date and set time or date: Retrieve or update current time/date.

• get/set system data: Manage general system information.

• get/set process, file, or device attributes: Access and modify attributes related to processes, files, and devices.

Communication System Calls

• Purpose of Communication System Calls: These calls facilitate communication between processes or devices. They are crucial for ensuring that processes can share information effectively during execution.

• Creating Communication Connections: To enable communication between two processes, connections must be created and deleted post-interaction. This requires specific system calls for establishing these links.

• Message Sending/Receiving: Processes may need to send or receive messages during their interactions, which is another critical function of communication-related system calls.

• Status Information Transfer: Processes communicate their status (e.g., completion of tasks or resource requests), necessitating dedicated calls for transferring this information effectively.

• Remote Device Management: Attaching/detaching remote devices also relies on communication protocols; thus, appropriate calls are needed for managing these connections efficiently.

Recap of Major Categories

• The five major categories of system calls discussed include:

• Process Control

• File Manipulation

• Device Management

• Information Maintenance

• Communication