Chapter 3 : Operating System Structures

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Chapter 3 : Operating System Structures by Mind Map: Chapter 3 : Operating System  Structures

1. Operating System Design : -Design and Implementation of OS not “solvable”, but some approaches have proven successful. -Start by defining goals and specifications . -The design of the system will be affected by the choice of hardware and the type of system: batch, time shared, single user, multiuser, distributed, real time or general purpose.

1.1. Goal :

1.1.1. 1. User goals – operating system should be convenient to use, easy to learn, reliable, safe, and fast.

1.1.2. 2. System goals – operating system should be easy to design, implement, and maintain, as well as flexible, reliable, error-free, and efficient.


2.1. - Contains only essential core operating systems functions

2.2. -Many services traditionally included in the operating system are now external subsystems

2.2.1. - Device drivers - File systems - Virtual memory manager - Windowing system - Security services

2.3. -Small operating system core

2.4. -Benefit :

2.4.1. -Extensibility -Flexibility -Reliability -Portability

3. Operating System Services : 1. User interface - Almost all operating systems have a user interface. 2. Program execution – The system must be able to load a program into memory and to run that program, end execution, either normally or abnormally. 3. I/O operations – Since user programs cannot execute I/O operations directly, the operating system must provide some means to perform I/O. 4. File-system manipulation – Program capabilities to read and write files and directories, create and delete them, search them, list file Information, permission management. 5. Communications – Processes may exchange information, on the same computer or between computers over a network 6. Error detection – Ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs.

4. Additional Operating System Functions : Protection and security - The owners of information stored in a multi-user or networked computer system may want to control use of that information, concurrent processes should not interfere with each other.

5. System Calls

5.1. 1. System calls provide the interface between a running program and the operating system.

5.1.1. 1.1 Generally available as assembly-language instructions. 1.2 Languages defined to replace assembly language for systems programming allow system calls to be made directly

5.2. 2. Three general methods are used to pass parameters between a running program and the operating system.

5.2.1. 2.1 Pass the parameters in registers. 2.2 Parameters stored in a block, or table, in memory, and address of block passed as a parameter in a register. 2.3 Parameters placed, or pushed, onto the stack by the program and popped off the stack by the operating system.

5.3. 3. Types of System Calls

5.3.1. - Process control - File management - Device management - Information maintenance - Communications - Protection

6. Communication Models : -Communication may take place using either message passing or shared memory

7. Layered Approach : i)In layered approach, the operating system 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. ii)With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers.

7.1. 1. Advantage - Simplicity of construction and debugging 2. Disadvantages - The careful definition and interaction of the layers - Less efficient