Chapter 2.2 Operating-System StructuresChapter 2: Operating-System StructuresFocus on Chapter 2.25. System ProgramsSystem Programs – Overview by Category6 Operating System Design and ImplementationOperating System Design and Implementation (Cont.)Advantages / Disadvantages of OS written in Higher Level Languages7 Operating System Structure Simple Structure7.1 Simple StructureMS-DOS Layer Structure7.1 Simple Structure (continued)UNIX System Structure7.2 Layered ApproachLayered Design Approach - AdvantagesLayered Design Approach - DisadvantagesLayered Operating System7.3 Microkernel System Structure DesignMicrokernel System Structure Design7.4 Modular System Structural DesignSolaris Modular Approach8 Virtual MachinesVirtual Machines (Cont.)Virtual Machines – Sharing DiskVirtual Machines - ImplementationVirtual Machines (cont) – Benefits:VMwareVMware ArchitectureThe Java Virtual MachineThe Java Virtual Machine (JVM) - implementation9. Operating System GenerationSystem BootingSlide 33End of Chapter 2Chapter 2.2 Operating-System Chapter 2.2 Operating-System StructuresStructuresModified Considerably by your Instructor352.2Silberschatz, Galvin and Gagne ©2005Operating System ConceptsChapter 2: Operating-System StructuresChapter 2: Operating-System Structures(Continued from Chapter 2.1 slides)System ProgramsOperating System Design and ImplementationOperating System StructureVirtual MachinesOperating System GenerationSystem Boot2.3Silberschatz, Galvin and Gagne ©2005Operating System ConceptsFocus on Chapter 2.2Focus on Chapter 2.2Is the Structure of an operating system.Will start off by looking at ‘system programs.’To start of discussing systems programs, we need to recall the hardware hierarchy.2.4Silberschatz, Galvin and Gagne ©2005Operating System Concepts5. System Programs5. System ProgramsLet’s recall the architectural hierarchy: (going ‘up’…)HardwareOperating system sits on top of the hardware and is very hardware dependent in many places.System Programs A number are conveniences for us, as in supplying user interfaces to system callsMany are quite complex and low levelA number of these are utilities to assist us too.Application Programs.Programs that provide functionality to the users.Let’s look at some typical categories of system programs as well as some samples.2.5Silberschatz, Galvin and Gagne ©2005Operating System ConceptsSystem Programs – Overview by System Programs – Overview by CategoryCategoryFile manipulation Used to create, delete, copy, print, list, move, etc.Status informationPrograms ask for time, number of users, sometimes request debugging information; File modificationCreate, modify, search, etc. May include text editors, search algorithms for files, etc.Programming language supportCompilers, debuggers, interpreters…Program loading and executionLoaders, linkage editors, absolute / relocatable loaders, overlay loaders, and moreCommunicationsCreating virtual connections among processes, users, and computing systems.Browse web pages, electronic mail, remote log in, transfer files, etc.Application programsMost computing systems also have programs to solve useful problems, such as word processors, text formatters, spreadsheets, compilers, database systems, etc.Most users’ view of the operation system is defined by system programs and the application programs, not the actual system callsApplication programs have little or no knowledge of underlying system calls when their programs request service.2.6Silberschatz, Galvin and Gagne ©2005Operating System Concepts6 Operating System Design and Implementation6 Operating System Design and ImplementationNo simple solution to design / implement an operating system.Hardware influences the design and the type of systembatch, time shared, multi-user, etc.But in general no cookbook design approach.A highly-creative, very complex, exacting undertaking! Two general groups of goals to consider in considering a design of an operating system. User goals andSystem goalsUser Goals: utility, learnability, usability, reliability, speed, – but there’sno solid agreement on how to achieve these.System Goals: Same: reliable, flexible, efficient, etc. – but no solid agreement on how these requirements can be specifically met.2.7Silberschatz, Galvin and Gagne ©2005Operating System ConceptsOperating System Design and Implementation (Cont.)Operating System Design and Implementation (Cont.)Most older operating systemswritten in assembler language, such as MSDOS, which (written in 8088 assembler language), This version of DOS was only available on the Intel family of CPUsTended to be very architecture dependent (register number, size, etc.)Modern systems are normally Almost totally written in C or C++ with some special routines written in assembler language (super efficient speeds)Higher level language implementation offers many advantages over assembler-constructed systems. Among these are:faster construction, ease of understanding and relative ease of debuggingAlso easier to recompile when changed, and port to other hardware.Higher level language construction disadvantages: reduced speed and increased storage capacities but with modern technologies, these are not significant.2.8Silberschatz, Galvin and Gagne ©2005Operating System ConceptsAdvantages / Disadvantages of OS written Advantages / Disadvantages of OS written in Higher Level Languagesin Higher Level LanguagesBut:Improvement in algorithm usage and data structures can improve performance better than programming in assembler languages. And, Only a small part of the operating system is absolutely critical to overall performance (memory manager and CPU scheduling).Parts of these can be fine-tuned with selective assembler coding.So we can see that most operating systems are written essentially in higher level languages.This has been the case for many years now.2.9Silberschatz, Galvin and Gagne ©2005Operating System Concepts7 Operating System Structure 7 Operating System Structure Simple Structure Simple Structure In this section, we’ll look at some approaches to structuring an operating system.Before we go into Virtual Machines, we will consider different structural