1. Operating System Structure
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

2. Virtual Machines
A virtual machine takes the layered approach to its logical conclusion. It treats hardware and the operating system kernel as though they were all hardware
A virtual machine provides an interface identical to the underlying bare hardware
The operating system creates the illusion of multiple processes, each executing on its own processor with its own (virtual) memory
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

3. Virtual Machines (Cont.)‏
The resources of the physical computer are shared to create the virtual machines
CPU scheduling can create the appearance that users have their own processor
Spooling and a file system can provide virtual card readers and virtual line printers
A normal user time-sharing terminal serves as the virtual machine operator’s console
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

4. Virtual Machines (Cont.)‏
(a) Nonvirtual machine (b) virtual machine
Non-virtual Machine
Virtual Machine
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

5. Virtual Machines (Cont.)‏
The virtual-machine concept provides complete protection of system resources since each virtual machine is isolated from all other virtual machines. This isolation, however, permits no direct sharing of resources.
A virtual-machine system is a perfect vehicle for operating-systems research and development. System development is done on the virtual machine, instead of on a physical machine and so does not disrupt normal system operation.
The virtual machine concept is difficult to implement due to the effort required to provide an exact duplicate to the underlying machine
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

6. VMware Architecture
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

7. The Java Virtual Machine
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

8. Operating System Generation
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

9. Operating System Generation
An operating system is designed to run on various kinds of computers; the system must be configured for each specific computer platform
The system generation program obtains information concerning the specific configuration of the hardware system and the desired configuration of the system software
Kinds of information obtained
Type of CPU, CPU options
Amount of memory
Available devices (type, number, interrupt number)‏
Operating system options
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

10. System Boot
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot

11. System Boot Booting – starting a computer by loading the kernel
The operating system must be made available to hardware so hardware can start it
When power is initialized on a computer system, execution starts at a fixed memory location
Firmware (ROM) is used to hold the initial boot code
This small piece of code – the bootstrap program or bootstrap loader, locates the kernel in ROM or on a hard disk , loads it into memory if necessary, and starts it
Sometimes this is a two-step process
The bootstrap program first runs the code in the boot block located at a fixed location on the hard disk
The code in the book block is then executed to load the operating system
22/01/207
Ms.S.Saranay/ AP/CSE Operatin Systems- Structure- Virtual Machine, OS Generation and System Boot