OS: Case Study 1

Give an example OS (Specific) for each of the following categories of OS:
State its description and other specifications.

• Batch Systems

Example:
• The University of Michigan Executive System, or UMES, a batch operating system developed at the University of Michigan in 1958, was widely used at many universities. Based on the General Motors Executive System for the IBM 701, UMES was revised to work on the mainframe computers in use at the University of Michigan during this time (IBM 704, 709, and 7090) and to work better for the small student jobs that were expected to be the primary work load at the University.
UMES was in use at the University of Michigan until 1967, when MTS was phased in to take advantage of the newer virtual memory time-sharing technology that became available on the IBM System/360 Model 67.

• IBSYS was the tape based operating system that IBM supplied with its IBM 7090 and IBM 7094 computers. A similar operating system (but with several significant differences), also called IBSYS, was provided with IBM 7040 and IBM 7044 computers. IBSYS was based on FORTRAN Monitor System (FMS) and SHARE Operating System.
IBSYS itself was really a basic monitor program, that read control card images placed between the decks of program and data cards of individual jobs. An IBSYS control card began with a "$" in column 1, immediately followed by a Control Name that selected the various IBSYS utility programs needed to set up and run the job. These card deck images were read from magnetic tapes, prepared offline, not usually directly from the punched card reader.

Advantages of batch systems

• move much of the work of the operator to the computer
• increased performance since it was possible for job to start as soon as the previous job finished
Disadvantages of batch systems
• turn-around time can be large from user standpoint
• more difficult to debug program
• due to lack of protection scheme, one batch job can affect pending jobs (read too many cards, etc)
• a job could corrupt the monitor, thus affecting pending jobs
• a job could enter an infinite loop


• Interactive Systems

Example:
Computer-aided technologies (CAx) is a broad term describing the use of computer technology to aid in the design, analysis, and manufacture of products.
Advanced CAx tools merge many different aspects of the product lifecycle management (PLM), including design, analysis using finite element analysis (FEA), manufacturing, production planning, product testing using virtual lab models and visualization, product documentation, product support, etc. CAx encompasses a broad range of tools, both those commercially available and those which are proprietary to the engineering firm.
The term CAD/CAM (computer-aided design and computer-aided manufacturing) is also often used in the context of a software tool covering a number of engineering functions.
Issues to be taken into account for interactive systems:
• User classes. Interactive systems often have varied classes of users with varying (potentially conflicting) requirements and expectations.
• Other systems. Interactive systems may interface with other systems in their environment.
• User interface. The ability to model and represent user interface requirements

Requirement issues for interactive systems:
• Indirect system concerns. These are issues related to system design and implementation, the influence of the system on the organisation and the system’s influence on the environment.
• Quality of service. The closeness of the system to the end-user lends special significance to quality of the service delivered. Quality concerns include:
• Availability
• Performance
• Usability
• Form of delivery



• Real-time systems

Example:
Xenomai is a real-time development framework cooperating with the Linux kernel, to provide a pervasive, interface-agnostic, hard real-time support to user space applications, seamlessly integrated into the Linux environment.
Xenomai is based on an abstract RTOS core, usable for building any kind of real-time interface, over a nucleus which exports a set of generic RTOS services. Any number of RTOS personalities called “skins” can then be built over the nucleus, providing their own specific interface to the applications, by using the services of a single generic core to implement it

An OS that can absolutely guarantee a maximum time for the operations it performs is referred to as hard real-time. In contrast, an OS that can usually perform operations in a certain time is referred to as soft real-time.
Jitter: The amount of error in the timing of a task over subsequent iterations of a program or loop is referred to as jitter. Real-time operating systems are optimized to provide a low amount of jitter when programmed correctly; a task will take very close to the same amount of time to execute each time it is run.
Figure: Jitter is a measure of how much the execution time of a task differs over subsequent iterations. Real-time operating systems are optimized to minimize jitter.
A Real-Time system is defined as a system whose correctness depends on the timeliness of its response. Examples of such systems are flight control systems of an aircraft, sensor systems in nuclear reactors and power plants. For these systems, delay in response is a fatal error. A more relaxed version of Real-Time Systems, is the one where timely response with small delays is acceptable. Example of such a system would be the Scheduling Display System on the railway platforms. In technical terminology, Real-Time Systems can be classified as:
• Hard Real-Time Systems - systems with severe constraints on the timeliness of the response.
• Soft Real-Time Systems - systems which tolerate small variations in response times.
• Hybrid Real-Time Systems - systems which exhibit both hard and soft constraints on its performance.


• Hybrid Systems

A computer system that performs two or more functions, such as data processing and word processing. A hybrid system is a dynamic system that exhibits both continuous and discrete dynamic behavior. Hybrid systems arise when the continuous and the discrete meet. Combine continuous and discrete inputs, outputs, states, or dynamics, and you have a hybrid system. Particularly, hybrid systems arise from the use of finite-state logic to govern continuous physical processes (as in embedded control systems) or from topological and network constraints interacting with continuous control (as in networked control systems).
Example: Hybrid systems have been used to model several systems, including physical systemswithimpact, logic-dynamiccontrollers, and even Internetcongestion. And one of the example of hybrid system is the bouncing ball.


• Embedded Systems

• A computer system that cannot be programmed by the user because it is preprogrammed for a specific task and embedded within the equipment which it serves.
Example:
NetBSD is a freely available open source version of the Unix-derivative Berkeley Software Distribution (BSD) computer operating system. It was the second open source BSD descendant to be formally released, after 386BSD,and continues to be actively developed. The NetBSD project is primarily focused on high quality design, stability and performance of the system.
NetBSD also provides system call-level binary compatibility on the appropriate processor architectures with several UNIX-derived and UNIX-like operating systems, including Linux, other BSD variants like FreeBSD, Apple's Darwin, Solaris and SunOS 4. This allows NetBSD users to run many applications that are only distributed in binary form for other operating systems, usually with no significant loss of performance.

In general, an Embedded System:
• Is a system built to perform its duty, completely or partially independent of human intervention.
• Is specially designed to perform a few tasks in the most efficient way.
• Interacts with physical elements in our environment, viz. controlling and driving a motor, sensing temperature, etc.