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1. Operating System Services

1.1. User interface

1.1.1. Almost all OS have a user interface (UI)

1.2. Program execution

1.2.1. The system must be able to load a program into memory and to run that program, end execution, either normally or abnormally(indicating error)

1.3. I/O operations

1.3.1. Since user programs cannot execute I/O operations directly, the OS must provide some means to perform I/O

1.4. File-system manipulation

1.4.1. Program capabilities to read and write files and directories, create and delete them, search them, list file Information, permission management

1.5. Communications

1.5.1. Processes may exchange information, on the same computer or between computers over a network

1.6. Error detection

1.6.1. Ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs

2. Layered Approach

2.1. the os is divided into a number of layers(levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest(layer N) is the user interface

3. Additional Operating System Funtions

3.1. Resource allocation

3.2. Accounting

3.3. Protection and Security

4. System Call

4.1. The purpose is to be used by an application program to invoke a function provided by OS

4.1.1. Types of System Call

4.1.2. Process control create process ,terminate process

4.1.3. File management Create file, delete file

4.1.4. Device management Request device, release device

4.1.5. Information maintenance Set time and date

4.1.6. Communication Create/delete communication connection

4.1.7. Protection Set permission

5. Communication Models

5.1. Memory Passing

5.1.1. communication takes places by means of messages exchanged between the processes

5.2. Shared Memory

5.2.1. A region of memory that is shared by processes can exchange information by reading and writing data to the shared region

6. Microkernel

6.1. Contains only essential core os functions

7. Operating System Design

7.1. User goals

7.1.1. OS should be convenient to use, easy to learn, reliable, safe, and fast.

7.2. System goals

7.2.1. OS should be easy to design, implement, and maintain, as well as flexible, reliable, error-free, and efficient