System call

2. System call provide the interface between a
process and the operating system. Certain
system allow system calls to be made directly
from a higher level language program, the calls
normally resembles predefined functions or
subroutine calls. They may generate a call to a
special run-time routine that makes the system
calls, or the system call may be generated
directly in line. These calls generally available as
assembly language instructions.

3. Example:-
Consider that we have to write a program to
read data from one file and to copy them to
another file. The first input that the program
will need is the names of the two files the
input file and the output file. In an interactive
system this approach will require a sequence
of system calls first to write a prompting
message on the screen and then to read from
the keyboard the characters that define the
two files. After file names are obtained each

4. Of these operations require another system
calls and may encounter possible error
conditions.
X: Parameters
for call
Load address X
System call 13
Use Parameters
from table X
X
User Program
Operating System

5. System Call can be grouped
into five major categories
Process Control
File Management
Device Management
Information Maintenance
Communications

6. Process Control
END, ABORT
Load, Execute
Create Process, Terminate Process
Wait Event, Signed Event
Allocate and free memory

7. File Management
Create File, Delete File
Open , Close
Read, write, reposition
Get file attributes, set file attributes

8. Device Management
Request device, Release Device
Read, Write, Reposition
Get Device attributes, set device attributes
Logically attach or detach device

9. Information Maintenance
Get time or date, set time or date
Get system date, set system date
Get process, device attributes

10. Communications
Create, delete communications connections
Send, Receive message
Transfer status information
Attach or detach remote devices

11. Sumant Kumar Diwakar
Web Designer