1. Operating System Overview
CS-550: Comparative Operating Systems

2. Operating System
A program that controls the execution of application programs
An interface between applications and hardware
CS-550: Comparative Operating Systems

3. Operating System Objectives
Convenience
Makes the computer more convenient to use
Efficiency
Allows computer system resources to be used in an efficient manner
Ability to evolve
Permit effective development, testing, and introduction of new system functions without interfering with service
CS-550: Comparative Operating Systems

4. Layers of Computer System
CS-550: Comparative Operating Systems

5. Services Provided by the Operating System
Program development
Editors and debuggers
Program execution
Access to I/O devices
Controlled access to files
System access
Error detection and response
Accounting
CS-550: Comparative Operating Systems

6. Operating System as Resource Manager
Responsible for managing all computer resources
Functions same way as ordinary computer software
It is program that is executed
Operating system relinquishes control of the processor to execute other programs
CS-550: Comparative Operating Systems

8. Kernel Portion of operating system that is in main memory
Contains most-frequently used functions
Also called the nucleus
CS-550: Comparative Operating Systems

9. Operating Systems History
Early 1950s:
Systems: Univac I, II; IBM 701, 704 – large, very expensive
Serial Processing
No operating system
Machines run from a console with display lights and toggle switches, input device, and printer
Common concerns:
Idle time between jobs
Setup: running a job included loading the compiler, source program, saving compiled program, and loading and linking
Every programmer writes routines to control I/O devices
CS-550: Comparative Operating Systems

10. First Generation: Simple Batch Systems
Eastern Joint Computer Conference in 1953: informal discussion of IBM users
GM develops input/output system for IBM 701
Common set of procedures for access to I/O devices
Monitor concept: Resides in main memory and controls the running programs; Batches jobs together; Program branches back to monitor when finished; Monitor starts next job
GM and North American Aviation jointly develop supervisor program for IBM 704
‘Share’ Operating System (SOS) developed by IBM on 709 for Share user group
Supervisory control, buffered I/O, symbolic assembly language
CS-550: Comparative Operating Systems

11. First Generation: Simple Batch Systems (Cont.)
Fortran Monitor System (FMS) on IBM 709
Based on GM/NAA OS, first OS to support high-level language programming
Real-Time and Transaction processing Systems
SAGE real-time control system (IBM AN/FSQ7 military system)
SABRE airline reservation system (IBM for American Airlines)
Tape Operating Systems
Card input and output temporarily stored on tape
Commonly used procedures (compilers) kept on tape
Examples: TOS/360 for first S/360, TOS for RCA Spectra 70
CS-550: Comparative Operating Systems

12. First Generation: Simple Batch Systems (Cont.)
Disk Operating Systems
Direct access to large amounts of data
Operating systems provided by computer manufacturer
Components: resident loader, Job Control Language (JCL), Input/Output Control System (IOCS)
Examples: Admiral for Honeywell 1800, EXEC I for Univac 1107, Scope for Control Data 6000, Master Control Program for Burroughs 5000, IBSYS for IBM 709 and 7090
ATLAS
Developed by Manchester Univ. and Ferranti
First use of interrupts, extracode (precursor of system call instruction), and one-level store (precursor of virtual memory)
CS-550: Comparative Operating Systems

13. First Generation: Batch Multiprogramming
Batch processing: each job submitted as a ‘batch’ of cards
Batch serial: jobs processed one at a time, each one finishing before new one accepted
Batch multiprogramming: several programs execute in interleaved manner and share CPU, memory, I./O devices – when a program waits for I/O completion, CPU given to other program
SPOOLing (Simultaneous Peripheral Operation On-Line)
Spooler program reads jobs from cards and tapes onto disk and copies output from disk to printer
CS-550: Comparative Operating Systems

14. First Generation: Batch Multiprogramming
Master Control Program (MCP) for Burroughs 5000 pioneered multiprogramming
Virtual memory
Priorities
High-level languages (Algol, Cobol) supported using compilers
IBM System/360 family (1964)
Evolvable: same program runs on entire family
DOS/360: interim disk OS
PCP: early version of OS/360
OS/MFT: batch multiprogramming for small S/360s
OS/MVT: batch multiprogramming for large S/360s
JCL: Large and powerful Job Control Language
CS-550: Comparative Operating Systems

15. Time-Sharing Systems Disadvantages of batch systems:
No direct user-program interaction
Long turnaround time
Interactive computing
User and system programs on disk
JCL commands entered by user directly on terminal
Time-sharing systems
Multiple users simultaneously access the system through terminals
Processor’s time is shared among the multiple users
Time slice (time quantum) limits the amount of time (CPU) received by each job
CS-550: Comparative Operating Systems

16. Time-Sharing Systems (Cont.)
Compatible Time-Sharing System (CTSS) developed in early 60s by Project MAC at MIT on IBM 709, then 7094
Dartmouth Time-Sharing System (DTSS)
Dartmouth College with General Electric
‘Basic’ language developed for use on DTSS
TOPS-10 developed by DEC for PDP-10
TSS/360 developed by IBM for 360/67
Virtual memory
CS-550: Comparative Operating Systems

17. Time-Sharing Systems (Cont.)
MULTICS developed by project MAC (MIT, Bell Labs, GE) as successor of CTSS (1964)
Hardware: modified GE635 (called GE645) with virtual memory and protection support
‘Computing Utility’ concept
Segmented virtual memory, linking and loading segments on demand, files and segments treated the same
‘Rings of protection’
Hierarchical file system
Device independence
I/O redirection
Powerful user interface
Written in a high-level language (PL/1)
CS-550: Comparative Operating Systems

18. Abstract and Virtual Machines
T.H.E. developed by Dijkstra at the Technological Univ. in Eindhoven, Holland in late 1960s
Major contributions to OS structuring and process synchronization
Structuring:
Hierarchical structure made of layers
Each layer, an abstract machine, i.e. apparent extension of real machine
Interacting processes (sharing common resources)
Semaphores for process synchronization
Deadlock solutions
CS-550: Comparative Operating Systems

19. Abstract and Virtual Machines (Cont.)
TENEX developed by Bolt, Beranek and Newman (BBN) for the PDP-10 in early 1970s
Time-sharing system with an abstract machine structure
CP/CMS (Control Program/Conversational Monitor System) developed by IBM Research in Cambridge, MA
Virtual machine concept: apparent access to all machine features (virtual memory, CPU, I/O devices)
Hardware shared by several OSs (some being developed)
Hardware:
Modified S/360 model 40 (CP/40)
Modified S/360 model 67 (CP/67)
Product: VM/370 on S/370
CS-550: Comparative Operating Systems

20. Minicomputer Operating Systems
Mid-1950s: Burroughs E-101, Bendix G-15, Librascope LGP-30
Machine language, no OS
Early 1960s: CDC-160, IBM-1620
Early 1970s: DEC OS-8 and TSS-8 for PDP-8
Interrupts, DMA
Disk Operating System for IBM 1800
Oss named ‘keyboard monitor’ and ‘real-time monitor’
Interactive interface for single user
Run one program at a time
Typical application: real-time control of lab. Operation
DEC PDP-11 series
OS (RT-11) simple single user
RSTS time-sharing system
RSX-11 real-time executive (multiprogramming, memory management, file system, powerful command language)
CS-550: Comparative Operating Systems

21. UNIX
Early 1970s: Bell Labs winds down MULTICS participation, Ken Thompson and Dennis Richie design a new OS
Hardware: PDP-7 then PDP-11
Key features
Hierachical file system
I/O devices, special cases of files
Powerful command language: ‘Shell’
Redirection: input/output from/to any sourse/destination in a Shell command
Concurrent processes with inter-process communication
Languages
Assembly language initially (PL/I not available for PDP)
Richie developed ‘C’ (BCPL  B  C)
‘C’ compiler for PDP-11 developed
UNIX re-written in ‘C’
CS-550: Comparative Operating Systems

22. Large Systems: Super-Minis and Main Frame Systems
VAX/VMS for the VAX family from DEC
Special instructions for OS support
Extensive system services
File management techniques
UNIX implemented on the VAX
OS/MVS (Multiple Virtual Storage)
Upgrade of OS/MVT for time-sharing (S/370) based on the Time-Sharing Option (TSO) developed for MVT
CS-550: Comparative Operating Systems

23. Operating Systems for Micros
Early OSs: MITS, IMSAI, Apple, Tandy, Heath develop simple OSs (loaders, ‘Basic’ language) running on Intel 8080, Zilog’s Z-80, Motorola’s 6800
CP/M (Control Program for Microprocessors)
Developed by Gary Killdall at Intel on 8008, then 8080
Single user OS
Simple interactive command interface
Basic I/O device management
Floppy disk based file system
Programming language for microprocessors (PL/M)
Killdall obtains rights to distribute CP/M, forms Digital Research
CP/M becomes dominant OS for micros
CS-550: Comparative Operating Systems

24. Operating Systems for Micros (Cont.)
CP/M limitations
Limited user interface, file, and device management
No memory management, no multiprogramming
SCP-DOS from Seattle Computer Products
Running on Intel 8086 (16-bit)
New features: memory management, timer management, interrupt support, sophisticated file system
MS-DOS: Upgraded SCP-DOS to run on several processors (SCP-DOS acquired by Microsoft)
PC-DOS: Version of MS-DOS selected by IBM to run on their PC
UNIX influence:
MS-DOS Version 2.0: Command interface like ‘Shell’, hierarchical file system
Later versions of MS-DOS: Multiple users, multiple processes
CS-550: Comparative Operating Systems

25. Major Achievements Processes Memory Management
Information protection and security
Scheduling and resource management
System structure
CS-550: Comparative Operating Systems

26. Processes Definitions for the term process Process components
A program in execution
An instance of a program running on a computer
The entity that can be assigned to and executed on a processor
A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources
Process components
An executable program
Associated data needed by the program
Execution context of the program or process state (e.g., contents of various processor registers, priority of the process)
CS-550: Comparative Operating Systems

27. Memory Management Process isolation
Automatic allocation and management
Support for modular programming
Protection and access control
Long-term storage
CS-550: Comparative Operating Systems

28. Information Protection and Security
Access control
Regulating user access to the total system, subsystems, and data
Regulating process access to various resources
Information flow control
Regulating the flow of data within the system and its delivery to users
Certification
Proving that access and flow control perform according to specifications and that they enforce desired protection and security policies
CS-550: Comparative Operating Systems

29. Scheduling and Resource Management
The operating system:
Manages the various resources: main memory space, I/O devices, and processors, and
Schedules their use by the active processes
The resource allocation and scheduling policy must consider:
Fairness
Give equal and fair access to all processes
Differential responsiveness
Discriminate between different classes of jobs with different service requirements
Efficiency
Maximize throughput, minimize response time, and accommodate as many users as possible
CS-550: Comparative Operating Systems

30. System Structure
The size and complexity of operating systems have significantly increased in time to meet the needs of new features and complex hardware:
CTSS: 32, bit words of storage
OS/360: 1 million machine instructions
MULTICS: 20 million instructions
Windows NT 4.0: 16 million lines of code
Windows 2000: 32 million lines of code
Methods for structuring operating system software
Modular software
Hierarchical structure: hierarchical layers and information abstraction
View the system as a series of levels
Each level performs a related subset of functions
Each level relies on the next lower level to perform more primitive functions
CS-550: Comparative Operating Systems

31. Operating System Design Hierarchy
Level Name Objects Example Operations
13 Shell User programming Statements in shell language
environment
12 User processes User processes Quit, kill, suspend, resume
11 Directories Directories Create, destroy, attach, detach,
search, list
10 Devices External devices: Open, close, read, write
printers, displays
and keyboards
9 File system Files Create, destroy, open, close
read, write
8 Communications Pipes Create, destroy, open. close,
CS-550: Comparative Operating Systems

32. Operating System Design Hierarchy
Level Name Objects Example Operations
7 Virtual Memory Segments, pages Read, write, fetch
6 Local secondary Blocks of data, Read, write, allocate, free
store device channels
5 Primitive processes Primitive process, Suspend, resume, wait, signal
semaphores, ready
list
4 Interrupts Interrupt-handling Invoke, mask, unmask, retry
programs
Procedures Procedures, call Mark stack, call, return
stack, display
2 Instruction Set Evaluation stack, Load, store, add, subtract
microprogram
interpreter
1 Electronic circuits Registers, gates, Clear, transfer, activate,
buses, etc. complement
CS-550: Comparative Operating Systems

33. Characteristics of Modern Operating Systems
Microkernel Architecture
Only a few essential functions are assigned to the kernel (address space, inter-process communication, and basic scheduling)
Other OS services are provided by processes (servers) that run in user mode
Symmetric MultiProcessing (SMP)
There are multiple processors
These processors share same main memory and I/O facilities and are interconnected by an internal connection scheme
All processors can perform the same functions
CS-550: Comparative Operating Systems

34. Characteristics of Modern Operating Systems
Multithreading: process is divided into threads that can run concurrently
Thread
Dispatchable unit of work
Includes processor context
executes sequentially and is interruptable
Process
A collection of one or more threads and associated system resources
CS-550: Comparative Operating Systems

35. Characteristics of Modern Operating Systems
Distributed operating systems
Provide the illusion of a single main memory and single secondary memory space
State of the art for distributed operating systems lags that of uniprocessor and SMP operating systems
Object-oriented design
Facilitates adding modular extensions to a small kernel
Enables programmers to customize an operating system without disrupting system integrity
CS-550: Comparative Operating Systems

36. Windows 2000 (W2K): Brief History
MS-DOS and PC-DOS
DOS 1.0 released in 1981 had 4,000 lines of assembly source code, ran in 8Kbytes of memory on a 8086
DOS 2.0 in 1983 ran on the IBM hard-disk based PC XT with 24Kbytes of memory resident OS
Support for hard disk
Hierarchical directories
UNIX-like features: I/O redirection and background printing
DOS 3.0 in 1984 ran on the PC AT (80286) with 36Kbytes
DOS 3.1, also in 1984, provided support for PC networking
DOS 3.3, in 1987 ran on IBM PS/2 with 46Kbytes
CS-550: Comparative Operating Systems

37. Windows 2000 (W2K): Brief History
Need for a new operating system
MS-DOS/PC-DOS did not use the full capabilities of the evolving processors: 80286, 80386, and then Pentium (e.g., extended addressing, memory protection)
To compete with Macintosh, in 1990 Microsoft developed a graphical user interface (GUI), Windows 3.0, that had to run on top of DOS
Microsoft and IBM attempt to jointly develop a common operating system; attempt fails; IBM develops OS/2 (multitasking, multithreaded), Microsoft develops Windows NT
CS-550: Comparative Operating Systems

38. Windows 2000 (W2K): Brief History
Windows NT
NT 3.1 released in 1993
32-bit operating system with ability to support older DOS and Windows applications, as well as provide OS/2 support
Same GUI as Windows 3.1
NT 3.x, several versions
NT 4.0
Same internal architecture as 3.x
Same user interface as Windows 98
Several graphics components moved to NT Executive (kernel mode)
Windows 2000 (W2K)
Same Executive and microkernel architecture as NT 4.0
New services and functions in support of distributed processing
W2K Professional vs. W2K Server
CS-550: Comparative Operating Systems

39. Single-User and Multi-User Multitasking
W2K (like OS/2 and MacOS) was design to exploit the capabilities of 32-bit microprocessors to meet the increasing needs of new applications
Motivations for multitasking
Applications have become more complex and interrelated (e.g., use of a word processor, a drawing program, and a spreadsheet application simultaneously for a document)
Growth of client/server computing: system needs to support user interaction concurrently with inter-processor communication
W2K Professional supports single-user multitasking, while W2K Server supports multi-user multitasking
CS-550: Comparative Operating Systems

40. Windows 2000 Architecture Modular structure for flexibility
Executes on a variety of hardware platforms
Supports application written for a variety of other operating system
Currently, W2K is only implemented on the Pentium/x86 platform
Separates application-oriented software from operating system software
OS software includes the Executive, the microkernel, device drivers, and the hardware abstraction layer and runs in kernel mode (access to system data and to hardware)
Application software runs in user mode and has limited access to user data
CS-550: Comparative Operating Systems

41. CS-550: Comparative Operating Systems 41

42. OS Organization Modified microkernel architecture
Not a pure microkernel: Many system functions outside of the microkernel run in kernel mode (reason: performance)
Highly modular structure
Each system function is managed by just one component of the OS: the rest of the OS and all applications access that component using a standard interface
Key system data can only be accessed through the appropriate function
Any module can be removed, upgraded, or replaced without rewriting the entire system
CS-550: Comparative Operating Systems

43. OS Organization – Layered Structure
Hardware Abstraction Layer (HAL): Maps between generic hardware commands and responses and those unique to a specific platform
Microkernel: Consists of the most used and most fundamental components of the OS. Manages thread scheduling, process switching, exception and interrupt handling, and multiprocessor synchronization. It does not run in threads: not preemptable nor pageable
Device Drivers: File system and hardware device drivers that translate user I/O function calls into specific hardware device I/O requests
I/O Manager: Dispatches requests to appropriate device drivers
Object Manager: Creates, manages, and deletes Executive objects
Security reference monitor: Enforces access-validation and audit-generation rules
Process/thread manager: Creates/deletes objects and tracks process and thread objects
Local Procedure Call (LPC) Facility: Enforces client/server relationship between applications and executive subsystems within a single system
CS-550: Comparative Operating Systems

44. OS Organization – Layered Structure Cont.)
Virtual memory manager: Maps virtual addresses in process’s address space to physical pages in memory
Cache manager: Improves performance of file-based I/O (read from cache, defer write)
Windows/graphics modules: Creates the windows-oriented screen interface and manages the graphics devices
User processes:
Special system support processes: Services not included in W2K (e.g., logon process)
Server processes: Other W2K services (e.g., event logger)
Environment subsystems: Supported subsystems are Win32, Posix, and OS/2
User applications: Can be of five types Win32, Posix, OS/2, Windows 3.1 or MS-DOS
CS-550: Comparative Operating Systems

45. Client/Server Model Operation:
A client (e.g., application program or another OS module) requests a service by sending a message
Message routed through the Executive to appropriate server
Server performs requested operation and returns results or status with another message
Message routed through Executive back to client
Advantages of client/server architecture:
Simplifies the Executive: possible to construct a variety of APIs
Improves reliability: clients cannot not directly access hardware
Provides a uniform means fro applications to communicate via LPC
Provides base for distributed computing
CS-550: Comparative Operating Systems

46. Threads and SMP W2K features that support threads and SMP:
OS routines can run on any available processor and different routines can execute simultaneously on different processors
Multiple threads of execution within a single process may execute on different processors simultaneously
Server processes may use multiple threads to process requests from many clients simultaneously
W2K provides mechanisms for sharing data and resources between processes and flexible interprocess communication capabilities
CS-550: Comparative Operating Systems

47. UNIX Brief history (cont.) Traditional UNIX system characteristics:
First widely available version outside Bell Labs was Version 6, in 1976
Version 7, released in in 1978, is the ancestor of modern UNIX systems
Most important non-AT&T development done at U. of C. at Berkeley, called UNIX BSD, running first on PDP, then VAX
In 1982, Bell Labs combined several AT&T versions into a system marketed as UNIX System III
A number of new features were developed to produce UNIX System V
Traditional UNIX systems: System V Release 3 (SVR3), 4.3BSD
Traditional UNIX system characteristics:
Hardware is surrounded by the operating-system called kernel
UNIX comes with a number of user services and interfaces (I.e., shell, other interface software, and the components of the C compiler)
Runs on a single processor and has limited protection capabilities
CS-550: Comparative Operating Systems

48. UNIX
CS-550: Comparative Operating Systems

49. Modern UNIX Systems System V Release 4 (SVR4) Solaris 2.x 4.4BSD Linux
Developed jointly by AT&T and Sun Microsystems, combined features from SVR3, 4.3BSD, Microsoft Xenix System V, and SunOS
New features: real-time processing support, process scheduling classes, dynamically allocated data structures, virtual memory management, virtual file system, and a preemptive kernel
Runs on machines ranging from 32-bit microprocessors up to supercomputers
Solaris 2.x
Sun’s SVR4-based UNIX release
Provides a number of advanced features: fully preemptable, multithreaded kernel, full support for SMP, and an object-oriented interface to file systems
Is is the most widely used and most successful commercial UNIX implementation
4.4BSD
Linux
CS-550: Comparative Operating Systems

50. Modern UNIX Systems (Cont.)
4.4BSD
Berkeley Software Distribution (BSD) series of UNIX releases has played a key role in the development of OS theory
Most enhancements to UNIX first appeared in BSD versions
4.xBSD is widely used in academic installations and has served as the basis of a number of commercial UNIX products
4.4BSD is the final version of BSD to be released by Berkeley and includes a new virtual memory system and changes in the kernel structure
Linux
CS-550: Comparative Operating Systems

51. Modern UNIX Systems (Cont.)
Linux
Started as a UNIX variant for the IBM PC architecture written by Linus Torvalds and posted on Internet in 1991
A large number of collaborators contributed to the development of Linux under the control of Torvalds
Linux is free and the source code is available under the auspices of the Free Software Foundation (FSF)
Today, Linux is a full-featured UNIX system running on a variety of platforms
Linux key advantages:
Modular structure: kernel organized as a collection of loadable modules; a module can be loaded and linked into the kernel while the kernel is in memory and executing
With source code available, vendors can tweak applications and utilities to meet specific requirements
CS-550: Comparative Operating Systems