iOSThe iOS is the operating system created by Apple Inc. for mobile devices. The iOS is used in many of the mobile devices for Apple such as iPhone, iPod, iPad etc. The iOS is used a lot and only lags behind Android in terms of popularity.The iOS architecture is layered. It contains an intermediate layer between the applications and the hardware so they do not communicate directly. The lower layers in iOS provide the basic services and the higher layers provide the user interface and sophisticated graphics.The layered architecture of iOS is given as follows −AndroidAndroid is an operating system ... Read More

Solaris is a Unix based operating system that was developed by Sun Microsystems and after its acquisition by Oracle it is known as Oracle Solaris. It is known for its scalability and its innovative features such as DTrace, ZFS, Time Slider etc.Solaris KernelThe kernel is the core of the operating system as its main function is to manage the hardware by allocating resources appropriately. Solaris is a microkernel design and it is not possible to create a monolithic Solaris kernel.Booting the kernel from a local disk in Solaris can be done using the following steps −Loading the bootblockReading and loading ... Read More

The interface between a process and an operating system is provided by system calls. In general, system calls are available as assembly language instructions. They are also included in the manuals used by the assembly level programmers. System calls are usually made when a process in user mode requires access to a resource. Then it requests the kernel to provide the resource via a system calls.In general, system calls are required in the following situations −If a file system requires the creation or deletion of files. Reading and writing from files also require a system call.Creation and management of new ... Read More

The iOS is the operating system created by Apple Inc. for mobile devices. The iOS is used in many of the mobile devices for apple such as iPhone, iPod, iPad etc. The iOS is used a lot and only lags behind Android in terms of popularity.The iOS architecture is layered. It contains an intermediate layer between the applications and the hardware so they do not communicate directly. The lower layers in iOS provide the basic services and the higher layers provide the user interface and sophisticated graphics.The layered architecture of iOS is given as follows −Layers in iOS ArchitectureThe different ... Read More

The Erasable Programmable Read Only Memory is a memory chip that does not lose data even when the power is switched off. This is a non-volatile memory type i.e. it retains data even when the power is switched off. Each EPROM is individually programmed by an electronic device. After that, the data can be erased by exposing the EPROM to strong ultraviolet light.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 from this window.EPROM OperationA single field effect transistor constitutes a storage location. This ... Read More

Android is an operating system developed by Google for mobile systems. It is based on the Linux kernel and mainly designed for touchscreen devices such as tablets and smartphones.The Android architecture is divided into four main layers and five sections. This is explained using the given diagram −The details about the different parts of the Android architecture are given as follows −ApplicationsThe android applications are in the top layer of the architecture. They are mainly written in Java and run within individual instances of the Dalvik virtual machine. The main features of the Android applications should be performance and efficiency, ... Read More

The Mac OS is a graphical operating system developed by Apple Inc. The tenth version of the Mac OS is the Mac OS X which was launched in 2001.The structure of the Mac OS X includes multiple layers. The base layer is Darwin which is the Unix core of the system. Next layer is the graphics system which contains Quartz, OpenGL and QuickTime. Then is the application layer which has four components, namely Classic, Carbon, Cocoa and Java. The top layer is Aqua, which is the user interface.A diagram that demonstrates the structure of Mac OS X is as follows ... Read More

Unix is a multiuser, multitasking operating system that was developed by Bell Laboratories in 1969. In a multiuser system, many users can use the system simultaneously. A multitasking system is capable of doing multiple jobs. Each user interacts with their own shell instance in this type of operating system and can start applications as required.An image that demonstrates the structure of the Unix operating system is −As seen in the image, the main components of the Unix operating system structure are the kernel layer, the shell layer and the application layer.Details about these are given as follows −KernelThe kernel provides ... Read More

Secondary storage devices are non-volatile devices where the data is stored for long-term storage. Disks are the mainly used secondary storage devices. They provide the bulk of secondary storage in operating systems today.The main activity that is performed in secondary storage management is disk scheduling. There are many disk scheduling algorithms. However, the important ones are FCFS scheduling, SSTF scheduling, SCAN scheduling and LOOK scheduling.All the disk scheduling algorithms are explained using the following requests for the disk -10, 95, 23, 78, 80First Come First Served SchedulingIn first come first served scheduling, the requests are serviced in their coming order. ... Read More

System programs provide an environment where programs can be developed and executed. In the simplest sense, system programs also provide a bridge between the user interface and system calls. In reality, they are much more complex. For example, a compiler is a complex system program.System Programs PurposeThe system program serves as a part of the operating system. It traditionally lies between the user interface and the system calls. The user view of the system is actually defined by system programs and not system calls because that is what they interact with and system programs are closer to the user interface.An ... Read More