FUNDAMENTALS OF OPERATING SYSTEM
Introduction to Operating System
An Operating System is defined as a group of programs which control the operation of a
computer system, manage hardware resources (CPU, memory, I/O, disk storage), provide a
platform for application programs to run, and provide services to the user.
The Operating System acts as an intermediary between the computer user and the computer
hardware.
USER
APPLICATION
PROGRAM
OPERATING
SYSTEM
COMPUTER
HARDWARE
Q. Explain four Operating System views.
Operating System Concepts
❖ Kernel – is the inner (core) component of the OS that manages and controls the
computer hardware. It runs all the time.
❖ Shell – is the outer component of the OS that allows the user to issue instructions or
commands to the kernel through an interface.
❖ Process – is a program currently under execution.
❖ System call – is a means by which a user program interacts with the OS. System call
allows a user program to request a service from the OS kernel.
Functions of OS
1. Process scheduling (Job scheduling) – in a multiprogramming situation the OS
determines which job is to be given CPU time and for how long. This ensures
maximum CPU utilization. In other words, the CPU does not stay idle.
Page 1 of 11
Prepared by Frank Okello
, FUNDAMENTALS OF OPERATING SYSTEM
• Multiprogramming is a technique used to execute multiple programs simultaneously by a
single processor.
2. Process management – the OS is responsible for process creation, suspension,
resumption, communication, synchronization and deletion.
3. Memory management – it keeps track of which memory blocks are currently being
occupied and which ones are not. It allocates memory space to programs opened by
the user and deallocates memory space from programs that are closed by the user.
4. File management – the OS helps the user to create, save, copy, move, rename and
delete files. It also enables the user to carry out file backup.
5. User interface – this is the method of interaction between the user and the computer
system. The OS provides user interface, thereby enabling the computer user interact
and use the computer system.
6. Secondary storage management – the OS it keeps track of which disk space
currently being occupied and which one is not.
7. Protection and security – the Operating System also enhances protection and
security of user data and programs from unauthorized access.
8. Error detection – the OS detects errors that might occur during program execution
such as memory error, device failure, attempt to access forbidden memory location,
etc. It then notifies the user through an error message and prompts them for an
appropriate corrective response. The corrective response could be either ending the
program that caused the error, retrying the operation or simply reporting the error to
the application.
9. Device management – it controls and manages communication between the
computer and any connected device through its device driver. It also manages data
transfer between the computer and the connected device. It also responds to
keystrokes and mouse clicks. In addition, the OS checks the status of a device to
determine if it is available (connected), busy or experiencing errors. Lastly, the OS
decides which program or user is to use a device when several programs require it –
this helps solve any conflicts that may arise when two or more programs require the
service of the same I/O device the same time.
10. Networking – the OS also manages communication and resource sharing between a
computer and other devices connected through a network.
11. Accounting – it records resource usage, tracks user activities, analyzes system
performance, preforms cost and billing calculations (in systems where users are
charged for resource usage).
12. Logging – the OS records system events and activities for the purposes of
troubleshooting, auditing and security.
Page 2 of 11
Prepared by Frank Okello
Introduction to Operating System
An Operating System is defined as a group of programs which control the operation of a
computer system, manage hardware resources (CPU, memory, I/O, disk storage), provide a
platform for application programs to run, and provide services to the user.
The Operating System acts as an intermediary between the computer user and the computer
hardware.
USER
APPLICATION
PROGRAM
OPERATING
SYSTEM
COMPUTER
HARDWARE
Q. Explain four Operating System views.
Operating System Concepts
❖ Kernel – is the inner (core) component of the OS that manages and controls the
computer hardware. It runs all the time.
❖ Shell – is the outer component of the OS that allows the user to issue instructions or
commands to the kernel through an interface.
❖ Process – is a program currently under execution.
❖ System call – is a means by which a user program interacts with the OS. System call
allows a user program to request a service from the OS kernel.
Functions of OS
1. Process scheduling (Job scheduling) – in a multiprogramming situation the OS
determines which job is to be given CPU time and for how long. This ensures
maximum CPU utilization. In other words, the CPU does not stay idle.
Page 1 of 11
Prepared by Frank Okello
, FUNDAMENTALS OF OPERATING SYSTEM
• Multiprogramming is a technique used to execute multiple programs simultaneously by a
single processor.
2. Process management – the OS is responsible for process creation, suspension,
resumption, communication, synchronization and deletion.
3. Memory management – it keeps track of which memory blocks are currently being
occupied and which ones are not. It allocates memory space to programs opened by
the user and deallocates memory space from programs that are closed by the user.
4. File management – the OS helps the user to create, save, copy, move, rename and
delete files. It also enables the user to carry out file backup.
5. User interface – this is the method of interaction between the user and the computer
system. The OS provides user interface, thereby enabling the computer user interact
and use the computer system.
6. Secondary storage management – the OS it keeps track of which disk space
currently being occupied and which one is not.
7. Protection and security – the Operating System also enhances protection and
security of user data and programs from unauthorized access.
8. Error detection – the OS detects errors that might occur during program execution
such as memory error, device failure, attempt to access forbidden memory location,
etc. It then notifies the user through an error message and prompts them for an
appropriate corrective response. The corrective response could be either ending the
program that caused the error, retrying the operation or simply reporting the error to
the application.
9. Device management – it controls and manages communication between the
computer and any connected device through its device driver. It also manages data
transfer between the computer and the connected device. It also responds to
keystrokes and mouse clicks. In addition, the OS checks the status of a device to
determine if it is available (connected), busy or experiencing errors. Lastly, the OS
decides which program or user is to use a device when several programs require it –
this helps solve any conflicts that may arise when two or more programs require the
service of the same I/O device the same time.
10. Networking – the OS also manages communication and resource sharing between a
computer and other devices connected through a network.
11. Accounting – it records resource usage, tracks user activities, analyzes system
performance, preforms cost and billing calculations (in systems where users are
charged for resource usage).
12. Logging – the OS records system events and activities for the purposes of
troubleshooting, auditing and security.
Page 2 of 11
Prepared by Frank Okello
