Job Description: Operating Systems Specialist

Introduction to Operating Systems:

Application software performs specific tasks for the user. System software operates and controls the computer system and provides a platform to run application software. An operating system is a piece of software that manages all the resources of a computer system, both hardware and software, and provides an environment in which the user can execute his/her programs in a convenient and efficient manner by hiding underlying complexity of the hardware and acting as a resource manager.

Why OS?

What if there is no OS? Bulky and complex app. (Hardware interaction code must be in app’s code base)
Resource exploitation by 1 App.
No memory protection.

What is an OS made up of?

Collection of system software.

Operating System Function:

Access to the computer hardware.
Interface between the user and the computer hardware.
Resource management (memory, device, file, security, process, etc.)
Hides the underlying complexity of the hardware (Abstraction).
Facilitates execution of application programs by providing isolation and protection.

OS Goals:

Maximum CPU utilization
Less process starvation
Higher priority job execution

Types of Operating Systems:

MS DOS, 1981
ATLAS, Manchester Univ., late 1950s – early 1960s
Multiprogramming operating system
Single process operating system
Batch-processing operating system
Multitasking operating system
Multi-processing operating system
Distributed system
Real-time OS
CTSS, MIT, early 1960s
Windows NT
LOCUS
ATCS

Multi-Tasking vs Multi-Threading:

The execution of more than one task simultaneously is called multitasking. A process is divided into several different sub-tasks called threads, which has its own path of execution. This concept is called multithreading.

Components of OS:

Kernel: Interacts directly with the hardware and performs the most crucial tasks.
User space: Where application software runs, apps don’t have privileged access to the underlying hardware.
Shell: Command interpreter that receives commands from the users and gets them executed.

Functions of Kernel:

Process management
Memory management
File management
I/O management

Types of Kernels:

Monolithic kernel
Micro Kernel
Hybrid Kernel
Nano/Exo kernels

System Calls:

How do apps interact with Kernel? Using system calls. Examples include process control, file management, device management, information maintenance, and communication management.

Deadlock:

In a multi-programming environment, several processes compete for finite resources. Deadlock occurs when processes are waiting for resources that are held by other processes.

Memory Management Techniques:

Contiguous Memory Allocation
Paging
Segmentation

Virtual Memory:

Allows execution of processes that are not completely in memory. Provides user an illusion of having a very big main memory.

Page Replacement Algorithms:

FIFO
Optimal page replacement
Least-recently used (LRU)
Counting-based page replacement

Thrashing:

Occurs when a process doesn’t have the number of frames it needs to support pages in active use, leading to high paging activity.