What is Hard disk and what is its purpose

Hard disk is the secondary storage device, which holds the data in bulk, and it holds the data on the magnetic medium of the disk.

Hard disks have a hard platter that holds the magnetic medium, the magnetic medium can be easily erased and rewritten, and a typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files. 

Real-Time System

A real time process is a process that must respond to the events within a certain time period. A real time operating system is an operating system that can run real time processes successfully

Difference between Hard and Soft real-time systems: 

                        A hard real-time system guarantees that critical tasks complete on time. This goal requires that all delays in the system be bounded from the retrieval of the stored data to the time that it takes the operating system to finish any request made of it.

                        A soft real time system where a critical real-time task gets priority over other tasks and retains that priority until it completes. As in hard real time systems kernel delays need to be bounded

Important aspect of a real-time system or Mission Critical Systems:

                        A real time operating system has well defined fixed time constraints. Process must be done within the defined constraints or the system will fail. An example is the operating system for a flight control computer or an advanced jet airplane. Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Real-Time systems may be either hard or soft real-time.

Hard real-time:

v  Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM)

v  Conflicts with time-sharing systems, not supported by general-purpose operating systems.

Soft real-time:

v  Limited utility in industrial control of robotics

Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.

Processor, assembler, compiler, loader, linker and the functions executed by them

Processor:--A processor is the part a computer system that executes instructions .It is also called a CPU

Assembler: -- An assembler is a program that takes basic computer instructions and converts them into a pattern of bits that the computer's processor can use to perform its basic operations. Some people call these instructions assembler language and others use the term assembly language.

Compiler: --- A compiler is a special program that processes statements written in a particular programming language and turns them into machine language or "code" that a computer's processor uses. Typically, a programmer writes language statements in a language such as Pascal or C one line at a time using an editor. The file that is created contains what are called the source statements. The programmer then runs the appropriate language compiler, specifying the name of the file that contains the source statements.

Loader:--In a computer operating system, a loader is a component that locates a given program (which can be an application or, in some cases, part of the operating system itself) in offline storage (such as a hard disk), loads it into main storage (in a personal computer, it's called random access memory), and gives that program control of the compute

Linker: -- Linker performs the linking of libraries with the object code to make the object code into an executable machine code.

Basic functions of an operating system

Operating system controls and coordinates the use of the hardware among the various applications programs for various uses. Operating system acts as resource allocator and manager. Since there are many possibly conflicting requests for resources the operating system must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls the user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.