Programs To Access System Resources

CHAPTER THREE
3.0    DETAILED REVIEW ON THE THEORIES AND PRINCIPLE OF OPERATING SYSTEM
An operating system is the largest and the most complicated software running on most machines. By knowing how operating system work, we learn how to organize a large piece of software (system design), how to hide complexity (abstraction), how to tune a large system (performance), and how to share software and hardware components in a safe, efficient, and fair manner (resource coordination). The skill set obtained from this course is directly applicable to advanced areas of computer science (e.g. software engineering, database, network and distributed computing).
An operating system is a virtual machine (emulated hardware) that aims to provide a simpler programming than the raw machine.

In some sense, the operating system is just a solution ti a software engineering problem. How do you hide the complexity and limitations of hardware from application programmer?
The design of each operating system component begins with the following two questions:
1.    What is the hardware interface? (the physical reality)
2.    What is the application interface (the nicer abstraction)
For different areas of the operating system, these two questions take forms in different ways: How to make a single CPU appear to be multiple CPU’s? How to make limited memory capacity appear to be infinite? How to make mechanical disk appear to be as fast as electronic memory?
How make insecure, unreliable network transmissions appear to be reliable and secure? How to make many physical machines appear to be a single machine?
Two General Functions of Operating Systems
A typical operating system provides two core sets of functions:
1.    Standard services consists of common facilities, such as screen display and disk access.
2.    Coordination allows multiple application to work together in safe efficient, and fair ways.
In nutt’s textbook, he uses resources to illustrate the same point. Resources are generally required software or hardware components for a computation. Standard services provide a way to hide the complexity of hardware resources and coordination allows safe, efficient, and fair ways of resources sharing.
3.1    STANDARD SERVICES
One example of standard service is accessing a disk drive. A simple conceptual model of a disk consist of a comb of disk arm and disk platters.