Quantum Computing – The Next Tech Revolution Technology has evolved rapidly over the last few decades—from bulky mainframe computers to powerful smartphones in our pockets. Yet, despite these advances, traditional computers are approaching their physical limits. This is where quantum computing enters the scene, promising to revolutionize the way we process information and solve complex problems. What Is Quantum Computing? Quantum computing is a new paradigm of computing that uses the principles of quantum mechanics, a branch of physics that explains how matter and energy behave at the smallest scales. Unlike classical computers, which use bits that represent either 0 or 1, quantum computers use qubits. Qubits can exist in multiple states simultaneously, thanks to a property called superposition. Additionally, qubits can be interconnected through entanglement, allowing them to share information instantaneously. These unique properties give quantum computers immense computational power....
1. modern operating systems are interrupt driven. If there are no processes to execute, no I/O devices to service, and no users to whom to answer, an operating system will sit quietly, waiting for something to happen.
2. A trap is a software-generated interrupt caused either by an error or by a particular request from a user program that an operating-system service is performed.
3. The interrupt-driven nature of an operating system defines system's general structure. For each type of interrupt, separate segments of codes in the operating system determine what action should be taken. An interrupt service routine is provided that is the responsible for dealing with the interrupt.
4. The operating system and the users share the hardware and software resources of the computer system, we need to make sure that an error in a user program could cause problem only for the one program that was running. With sharing, many processes could be adversely affected by a bug in one program. For example, if a process gets stuck in an infinite loop, this loop prevents the correct operation of many other processes.
5. Without protection against these sorts of errors, either the computer must execute only one process at a time or all output must be suspect.
Dual-mode operation:
Dual-mode operation allows Operation system to guard itself and the other system components User mode and kernel
mode.
Some instructions designated as authority, only executable in kernel mode System call changes mode to kernel, return from call resets it to user
Transition from User to Kernel Mode
* Timer to prevent infinite loop / process monopolize resources Set interrupt after specific period
* Operating system decrements counter
* When counter zero generate an interrupt
* Set up before scheduling process to recover control or terminate program that exceeds allotted time.
If a computer system has multiple users and allows the concurrent execution of multiple processes, then access to data must be regulated. For that purpose, mechanisms ensure that files, memory segments, CPU, and other resources can be operated on by only those processes that have gained proper consent from the operating system.
Protection and security
Protection is any mechanism for controlling the availability of processes or users to the resources defined by a
computer system. This mechanism must provide means for specification of the controls to be resist and means for enforcement.
Protection can improve accuracy by detecting latent errors at the interfaces between component subsystems. Early detection of interface errors can often prevent polluting of a healthy subsystem by another subsystem that is malfunctioning.
An unprotected resource cannot defend against use (or misuse) by an unauthorized or incompetent user. A protection-oriented system provides a means to distinguish between authorized and unauthorized usage, A system can have sufficient protection but still be prone to failure and allow inappropriate access.
It is the job of security to protect a system from external and internal attacks. Such attacks spread across a huge range and include viruses and worms, denial-of service attacks Protection and security
require the system to be able to differentiate among all its users. Most operating systems maintain a list of
user names and related user identifiers (user IDs).
* User ID then declarative with all files, processes of that user to determine access control
* Group identifier (group ID) allows set of users to be defined and controls managed, then also associated with each process, file Privilege incision allows user to change to effective ID with more rights
Kernel Data Structures:
The operating system must keep a lot of information about the current situation of the system. As things happen within the system these data structures must be changed to contain the current reality. For example, a new process might be created when a user logs onto the system.
The kernel must create a structure of the data representing the new process and link it with the data structures representing all of the other processes in the system.
Mostly these data structures exist in physical memory and are attainable only by the kernel and its subsystems. Data structures retain data and pointers, addresses of other data structures, or the
addresses of routines. Taken all together, the data structures used by the Linux kernel can look very difficult. Every data structure has a purpose and although some of them are used by several kernel subsystems, they are more easy than they appear at first sight.
Understanding the Linux kernel pivot on understanding its data structures and the use that the various functions within the Linux kernel makes of them. This section bases its description of the Linux kernel on its data structure. It briefs about each kernel subsystem in terms of its algorithms, which are its
methods of getting things done, and the usage of the kernel's data structures.