Operating System Services

1. provide interface between running program and operating system

2. System Calls

2.1. available as assembly-language instructions

2.2. used by an application program to initialize a function provided by os

3. Types of System Calls

3.1. Process control: Create or terminate process

3.2. File management: Create or delete files

3.3. Information maintenance: Set time and date

3.4. Communications: Create/delete communications connection

3.5. Device management: Release device

3.6. Protection: Set permission

4. Operating System Design Goals

4.1. User goals: convinient to use,easy to learn and fast

4.2. System goals: easy to design,implement,flexible and efficient

5. Types

5.1. User interface

5.2. Program execution

5.3. I/O opertions

5.4. File-system manipulation

5.5. Communications

5.6. Error detection

6. Additional OS Funtions

6.1. Resource allocation

6.2. Accounting

6.3. Protection and security

7. Microkernel

7.1. Small operating system core

7.2. Essential core operating systems functions

7.3. Provide communications facility between user program and various services

7.4. User program and service communicate directly by exchanging message with microkernel

8. Communication Models

8.1. Message passing: model communication takes place by means of messages exchnaged between process

8.2. Shared memory: model that is shared by processors exchange information by reading and writing data to the shared region