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Computer Science Articles
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MS-DOS Layered Structure
MS-DOS (Microsoft Disk Operating System) is a classic single-user operating system created for personal computers that exemplifies the layered architecture approach. The system is organized into distinct layers, each with specific responsibilities and well-defined interfaces for interaction with adjacent layers. The layered structure provides several advantages in MS-DOS. Each layer can be developed, maintained, and updated independently without affecting other layers. This modular approach simplifies system design and allows for easier debugging and enhancement. However, MS-DOS layers are not rigidly separated, and some layer specifications overlap, which can create dependencies between layers. MS-DOS Layered Architecture ...
Read MoreErasable Programmable Read Only Memory (EPROM)
Erasable Programmable Read Only Memory (EPROM) is a non-volatile memory chip that retains data even when power is switched off. Each EPROM is individually programmed by an electronic device, and the stored data can be erased by exposing the chip to strong ultraviolet light for reprogramming. An EPROM contains a transparent fused quartz window at the top of the package which allows exposure to ultraviolet light. The silicon chip is visible through this window, making it easily identifiable among other memory types. How EPROM Works Each storage location in EPROM consists of a floating-gate field-effect transistor. This ...
Read MoreHow are iOS and Android similar? How are they different?
iOS and Android are the two dominant mobile operating systems, powering billions of smartphones and tablets worldwide. While both serve similar core functions, they differ significantly in architecture, philosophy, and user experience. Understanding their similarities and differences helps users make informed decisions when choosing mobile devices. iOS Overview iOS is Apple's proprietary operating system designed exclusively for mobile devices including iPhone, iPad, and iPod Touch. It features a layered architecture with an intermediate layer between applications and hardware, ensuring they don't communicate directly. The lower layers provide basic services while higher layers handle user interface and graphics. ...
Read MoreSystem Calls in Unix and Windows
System calls provide the interface between a process and an operating system. They are available as assembly language instructions and serve as the only mechanism for user programs to access kernel services. System calls are similar to function calls but transfer control from user mode to kernel mode. How System Calls Work When a process needs operating system services, it makes a system call which triggers a software interrupt. The CPU switches from user mode to kernel mode, executes the requested service, and returns the result to the calling process. This mechanism ensures security and controlled access to ...
Read MoreHow does System Boot work?
The system boot process is the sequence of steps that occurs when a computer starts up, transforming it from a powered-off state to a fully operational system. The BIOS, operating system, and hardware components must all work correctly for successful booting. System Boot Process The boot process involves several distinct phases, each with specific responsibilities for system initialization. System Boot Process Flow Power On CPU Initialization ...
Read MoreLoadable Modules Architecture of the Operating System
Loadable kernel modules are object files containing code that extends the running kernel (also called the base kernel) of an operating system. These modules provide a flexible way to add support for new file systems, hardware drivers, system calls, and other kernel functionality without modifying the core kernel code. Loadable modules allow the operating system to dynamically load and unload kernel components as needed, making the system more modular and efficient. Loadable Modules Architecture Base Kernel Core OS Functions ...
Read MoreShared Memory Model of Process Communication
Process communication is the mechanism provided by the operating system that allows processes to communicate with each other. This communication could involve a process letting another process know that some event has occurred or transferring of data from one process to another. One of the models of process communication is the shared memory model. The shared memory in the shared memory model is the memory that can be simultaneously accessed by multiple processes. This is done so that the processes can communicate with each other. All POSIX systems, as well as Windows operating systems use shared memory. ...
Read MoreMutex vs Semaphore
Mutex and Semaphore are both synchronization mechanisms used in operating systems to coordinate access to shared resources between multiple threads or processes. While they serve similar purposes, they have distinct characteristics and use cases. Mutex A Mutex (Mutual Exclusion) is a locking mechanism that ensures only one thread can access a critical section at a time. It acts like a binary lock that can be either acquired or released by a thread. How Mutex Works wait(mutex); // Critical Section // Only one thread can execute here signal(mutex); Key characteristics of Mutex: ...
Read MoreMonitors vs Semaphores
Monitors and semaphores are synchronization mechanisms used to control process access to shared resources through mutual exclusion. While both achieve process synchronization, they differ significantly in their implementation, usage complexity, and error handling capabilities. Monitors Monitors are high-level synchronization constructs designed to overcome timing errors and programming complexity associated with semaphores. They are abstract data types that encapsulate shared data variables and procedures within a single unit. In a monitor, shared data variables cannot be accessed directly by processes. Instead, processes must use the monitor's procedures to interact with the shared data. Only one process can be ...
Read MoreZombie vs Orphan vs Daemon Processes
Operating systems manage different types of processes during their lifecycle. Three important categories are zombie processes, orphan processes, and daemon processes. Each serves a different purpose and behaves uniquely in the system. Zombie Processes A zombie process is a process whose execution has completed but still has an entry in the process table. This occurs because the parent process needs to read the child's exit status before the process can be fully removed from the system. Zombie Process Lifecycle Parent Running Child Running ...
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