Operating System
Services
• Operating systems provide an
environment for execution of programs
and services to programs and users
• One set of operating-system services
provides functions that are helpful to the
user:
• User interface - Almost all operating
systems have a user interface (UI).
• Varies between Command-Line (CLI),
Graphics User Interface (GUI), Batch
• Program execution - The system must be
able to load a program into memory and
to run that program, end execution, either
normally or abnormally (indicating error)
• I/O operations - A running program may
require I/O, which may involve a file or an
I/O device
Operating System
Services (Cont.)
• One set of operating-system services
provides functions that are helpful to the
user (Cont.):
, • File-system manipulation - The file system
is of particular interest. Programs need to
read and write files and directories, create
and delete them, search them, list file
Information, permission management.
• Communications – Processes may
exchange information, on the same
computer or between computers over a
network
• Communications may be via shared
memory or through message passing
(packets moved by the OS)
• Error detection – OS needs to be
constantly aware of possible errors
• May occur in the CPU and memory
hardware, in I/O devices, in user program
• For each type of error, OS should take the
appropriate action to ensure correct and
consistent computing
• Debugging facilities can greatly enhance
the user’s and programmer’s abilities to
efficiently use the system
Operating System
Services (Cont.)
• Another set of OS functions exists for
ensuring the efficient operation of the
system itself via resource sharing
• Resource allocation - When multiple users
or multiple jobs running concurrently,
resources must be allocated to each of them
,• Many types of resources - CPU cycles, main
memory, file storage, I/O devices.
• Accounting - To keep track of which users
use how much and what kinds of computer
resources
• Protection and security - The owners of
information stored in a multiuser or
networked computer system may want to
control use of that information, concurrent
processes should not interfere with each
other
• Protection involves ensuring that all access
to system resources is controlled
• Security of the system from outsiders
requires user authentication, extends to
defending external I/O devices from invalid
access attempts
, A View of Operating
System Services
User Operating System
Interface - CLI
CLI or command interpreter allows
direct command entry
• Sometimes implemented in kernel, sometimes by
systems program
• Sometimes multiple flavors implemented – shells
• Primarily fetches a command from user and
executes it
Services
• Operating systems provide an
environment for execution of programs
and services to programs and users
• One set of operating-system services
provides functions that are helpful to the
user:
• User interface - Almost all operating
systems have a user interface (UI).
• Varies between Command-Line (CLI),
Graphics User Interface (GUI), Batch
• Program execution - The system must be
able to load a program into memory and
to run that program, end execution, either
normally or abnormally (indicating error)
• I/O operations - A running program may
require I/O, which may involve a file or an
I/O device
Operating System
Services (Cont.)
• One set of operating-system services
provides functions that are helpful to the
user (Cont.):
, • File-system manipulation - The file system
is of particular interest. Programs need to
read and write files and directories, create
and delete them, search them, list file
Information, permission management.
• Communications – Processes may
exchange information, on the same
computer or between computers over a
network
• Communications may be via shared
memory or through message passing
(packets moved by the OS)
• Error detection – OS needs to be
constantly aware of possible errors
• May occur in the CPU and memory
hardware, in I/O devices, in user program
• For each type of error, OS should take the
appropriate action to ensure correct and
consistent computing
• Debugging facilities can greatly enhance
the user’s and programmer’s abilities to
efficiently use the system
Operating System
Services (Cont.)
• Another set of OS functions exists for
ensuring the efficient operation of the
system itself via resource sharing
• Resource allocation - When multiple users
or multiple jobs running concurrently,
resources must be allocated to each of them
,• Many types of resources - CPU cycles, main
memory, file storage, I/O devices.
• Accounting - To keep track of which users
use how much and what kinds of computer
resources
• Protection and security - The owners of
information stored in a multiuser or
networked computer system may want to
control use of that information, concurrent
processes should not interfere with each
other
• Protection involves ensuring that all access
to system resources is controlled
• Security of the system from outsiders
requires user authentication, extends to
defending external I/O devices from invalid
access attempts
, A View of Operating
System Services
User Operating System
Interface - CLI
CLI or command interpreter allows
direct command entry
• Sometimes implemented in kernel, sometimes by
systems program
• Sometimes multiple flavors implemented – shells
• Primarily fetches a command from user and
executes it
