What are the main types of system calls? Describe their purpose.

What are the main types of system calls? Describe their purpose.
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.
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.
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.