System Calls are used to show all services offered by the OS. It serves as an interface b/w user program and Operating System. The system call interface layer includes entrance point in kernel code. This topic is all about different types of system calls and their working.
System calls provide an interface between a user program and Operating System. The system calls expose the services offered by the operating system to user programs. These are set of functions methods. Most system calls are written in assembly language and are machine dependent. Numerous higher level languages such as ‘C’ also permit to make system calls directly.
The system call interface layer includes entrance point in kernel code. All system resources are managed and controlled by the kernel. Any request from user or application that occupies access to any system resource must be tackled by kernel code. The user process must not be given untie access to kernel code for security cause. Many opening into kernel code called system calls are provided to the user so that the user processes can raise the execution of kernel code.
System calls permit processes and users to Operating System resources.
There are three universal methods that are used to pass information between a running program and the Operating System.
- One technique is to store parameters in registers.
- Another is to store parameters in a table in memory and get ahead of the address of table.
- The third way is to push parameters on the stack and let operating system to pop the parameters off the stack.
Main Types of System Calls
The most important types of system calls are as follows:
- Process Control
- File Management
- Device Management
- Information Maintenance
These kinds of system calls are used to direct the processes. Some examples are end, abort, load, execute, create, process, terminate process etc.
These types of system calls are used to handle files. Some examples are create file , delete file, open, close, read, write etc.
These types of system calls are used to deal with devices. Some examples are request device, release device, read, write, get device attributes etc.
These types of system calls are used to maintain information. Some examples are get time or date, set time or date, get system data, set system data etc.
These types of system calls are used for communication. Some examples are create, delete communication connection, send, receive messages etc.
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