SYSTEM CALLS

1. SHADAN WOMEN’S COLLEGE OF
ENGINEERING & TECHNOLOGY
(An autonomous institution affiliated to JNTUH,Telengana)
NAME : ANUSHA ASHRAF
HT.NO. : 23L51A7205
SUBJECT : DBMS
CLASS : B.TECH 2ND
YEAR 2ND
SEM
BRANCH : AI&DS
TOPIC : SYSTEM CALLS

2. SYSTEM CALLS

3. 3
CONTENTS
o INTRODUCTION
o STRUCTURE OF SYSTEM CALLS
o HOW A SYSTEM CALL OCCURS
o CATEGORIES OF SYSTEM CALLS
o EXAMPLE OF SYSTEM CALL IN LINUX

4. INTRODUCT ION
 System Calls provide the Interface between a process and the
Operating System.
 These calls are generally available as Assembly language
instruction.
 System Calls can also be made directly through HLL programs
for certain systems.
 UNIX System calls can be invoked directly from a C or C++
program.

5. S TRUCTURE OF S YSTE M CAL LS
•User requests a system call (e.g., read()).
•Request goes to OS via a software
interrupt.
•Kernel handles the request and returns a
result to user space.

6. 6
HOW S YS TEM CAL LS OCCUR.
System Calls occur in different ways depending on the computer
in use:
o More information is required than just the identify of the
desired System call.
o The exact type and amount of information varies according to
the operation system and call
o For instance to get an input we need to specify the file of device
to use as source and the address and length of memory buffer

7. 7
CAT EGORIES OF SYS TEM CALL S
System calls can be grouped into five major categories as
follows.
o Process control
o File management.
o Device management
o Information Maintenance
o Communication.

8. 8
PROCES S CONTROL
Some system calls under process control
are:
o End, abort
o Load, execute
o Create process, terminate process
o Get process, terminate process
o Wait for time
o Allocate and free memory

9. 9
FI LE M ANAGEM ENT
Some system calls under file
management are:
o Create file, delete file
o Open , close
o Read, write, reposition.
o Get file attributes, set fil attributes

10. 10
DEVICE M ANAGEM ENT
Some system calls under device management
are:
o Request Device, release device
o Read, write, reposition.
o Get device attributes and set device attributes
o Logically attach or detach devices

11. 11
INFOR MATI ON M AINTENANCE
Some system calls under information maintenance are:
o Get time or date, Set time of date
o Logically attach or detach devices
o Information maintenance
o Get system data, Set Systems data
o Get process, file of device attributes
o Set process, file or device attributes

12. 12
COM M UNI CATI ON
o Create, delete communication
connection.
o Send, receive messages
o Transfer status information
o Attach or detach remote devices.

13. 13
EXAM PL E OF S YS TEM CALL S I N LI NUX
🔹 int fd = open("file.txt", O_RDONLY);
What it does:
Opens the file "file.txt" in read-only mode.Returns a file
descriptor (fd): a non-negative integer if successful, or -1 if
an error occurs.
🔹 ssize_t bytes = read(fd, buffer, size);
What it does:
Reads up to size bytes from the file referred to by
fd into buffer.Returns the number of bytes read, or
-1 on error.
🔹 pid_t pid = fork();
What it does:
Creates a new child process.Returns:>0 to the
parent (child's PID)0 to the child-1 on failure
OUTPUT :

14. CONCL US I ON
•System calls are essential for OS functionality.
•Provide a bridge between applications and hardware.
•Understanding system calls is crucial for low-level
programming and OS development.

15. THANK YOU