OS Services for users

1
OS Services for users

• User Interface
• Command Line Interface
• Interpreters are known as SHELL
• For UNIX and LINUX (Bourne Shell, C shell, Korn
  Shell)
• Commands include file manipulation (create,
  delete, list, print, execute a file, etc)
• Interpreter jumps to a section of its code that
  set up the parameters and makes the appropriate
  system call.
• Graphical User Interface Based on desktop
  (window), menu, icons, etc.

2
OS Services for users

• Program Execution
• OS loads program, execute it, and reports its
  normal or abnormal execution.
• I/O Operations
• OS provides the way to manipulate the I/O device
  for users.
• File System Manipulation
• File System used to execute system calls from
  users to manipulate their files. Create, delete,
  search inside a file, etc, are some file
  operations.
• Communications
• Controlled by OS either by sharing memory or by
  message passing.

3
OS Services for users

• Error Detection
• Error can occur in CPU, Memory, I/O devices or by
  program (division by zero, overflow, access to an
  illegal location, etc)
• Resource Allocation
• For multiple users or multiple jobs at the same
  time
• Scheduling is needed for each hardware
• Accounting
• OS keeps track of which users have how much and
  what kind of computer resources
• Protection and security
• Protection means all access to system resources
  must be controlled
• Security means the authentication using password.

4
System Call Definition
It is an interface to the service made available
by an operating system Examples are open, close,
read, write a file
Open Module
USERS
System Call
5
System Call Sequence(Copy a input file into
other file)
6
Application programming InterpreterAPI
HANDLE The file to be read LPVOID
buffer where data will be read into and written
from. DWORD Number of bytes to be read into
buffer LPDWORD Number of bytes read during
the last read. LPOVERLAPPED Indicates if
overlapped I/O is being used
7
2.03
8
2.04
9
2.06
10
2.07
11
2.08
12
2.09
13
2.10
14
2.11
15
2.12
16
2.13
17
2.14
18
2.15
19
2.16
20
2.17
21
2.18