1.The concept of Operating System:

it is a software that manages the computer hardware as well as providing an environment for application programs to run.

2.For a computer to do its job is executing programs and the programs must be in main memory. Main memory is the largest area for computer processor to access directly.

3.three strategies for designing a computer systems

1. Uniprocessor system: have only a single processor


2. multiprocessor system: contain two or more processors that share physical memory and peripheral but work independently of one another.


3. Clustered system: a specialized form of multiprocessor systems and consist of multiple computer systems connected by a local area network.

4.system-call level must provide the basic functions , such as process control and file and device manipulation.

5.System services can be classified into several categories: program control , status requests , and I/O requests.

6.operating system are now almost always written in a systems implementation language or in a higher-level languages. This features improves their implementation , maintenance and portability.

7.For a computer system starts running , the CPU must initialize and start executing the book-strap program in firmware. The book-strap system can execute the operating system directly if the operating system is also in the firm ware.