18/04/20151 Operating Systems Modes of Use / Operation On-Line & Real-Time

218/04/2015 Learning Objectives Discuss modes of computer use and the interrelationship between applications and modes of use. Describe the characteristics of different types of operating systems. Describe the uses of different types of operating systems.

318/04/2015 MultiprocessingInteractive Single-User Operating Systems (Types of / Modes of operation) BatchReal-time Network Multi-Access / User Multi-tasking Simple Client-Server Network System Distributed Network System Off-lineOn-line Time Slicing / Sharing This presentation focuses on these modes.

418/04/2015 On-line User has direct contact with processor Used when: Processor needs to be constantly ready to receive input Processor needs to be constantly ready to receive input Justified by: Explaining why processor needs to be constantly ready to receive input. Explaining why processor needs to be constantly ready to receive input. Or if real-time is necessary and has been justified then state: Or if real-time is necessary and has been justified then state: “On-line as otherwise system cannot be real-time.” Back

Data processed or action is taken at time of input, quickly enough to affect the next input. Is by definition also on-line. Used when a system must react immediately when input from a sensor or other input device is received as a delay is unacceptable. Used in process control or transaction processing. These are the two different types of real-time operating system. Justified by: Explaining what action must be taken immediately and why a delay is unacceptable.Real-time Disadvantage

618/04/2015 Transaction Processing Transaction processing systems also attempt to provide predictable response times to requests, although this is not as critical as for real-time systems. Rather than allowing the user to run arbitrary programs as time-sharing, transaction processing allows only predefined, structured transactions. Each transaction is usually short duration and the processing activity for each transaction is programmed in advance. Largely database related. IGCSE “Databases Quiz” & “Databases - Theory Test”. IGCSE “Databases Quiz” & “Databases - Theory Test”.Databases QuizDatabases - Theory TestDatabases QuizDatabases - Theory Test ict.com/gcse_new/computer%20systems/operating_system_types/mini web/pg7.htm ict.com/gcse_new/computer%20systems/operating_system_types/mini web/pg7.htm ict.com/gcse_new/computer%20systems/operating_system_types/mini web/pg7.htm ict.com/gcse_new/computer%20systems/operating_system_types/mini web/pg7.htm

718/04/2015 Process Control Process control is extensively used in industry and enables mass production of continuous processes such as oil refining, paper manufacturing, chemicals, power plants and many other industries. Process control enables automation, with which a small staff of operating personnel can operate a complex process from a central control room. Process control may either use feedback or it may be open loop. Control may also be continuous (car cruise control) or cause a sequence of discreet events, such as a timer on a lawn sprinkler or thermostat on a heater (on/off) or controls on an elevator (logical sequence). Note that sensors DO NOT turn output devices on/off (the CPU does this based on the readings it receives from sensors), although the page from Wikipedia below suggests that it does: See the IGCSE “Processing Quiz” and “Processing Test”. See the IGCSE “Processing Quiz” and “Processing Test”.Processing QuizProcessing TestProcessing QuizProcessing Test

Speed mismatch implications: The computer will not be using its full potential as far as processing is concerned. Because the computer cannot be using up some of its slack time doing other tasks while it is waiting to be asked to do something. Disadvantage of Real-time Examples

918/04/2015 Real-time Use & Justification 1 Driving a racing car around a track. Turning the wheel must turn the car immediately. Turning the wheel must turn the car immediately. Process control Next

1018/04/2015 Real-time Use & Justification 2 ATM computer system Checking of PIN/identification Checking of PIN/identification Checking of funds available Checking of funds available to ensure person has the right to extract cash, or long wait is possible Transaction processing Next

1118/04/2015 Real-time Use & Justification 3 A chemical plant has a reaction vessel where the temperature is critical to the result of the process. The temperature is monitored by a computer which accepts input from a sensor and then makes a decision whether to adjust the heating elements in the vessel. The temperature is monitored by a computer which accepts input from a sensor and then makes a decision whether to adjust the heating elements in the vessel. If there was a delay in the decision making process, it might mean that the reaction is corrupted in some way. Process control Next

1218/04/2015 Real-time Use & Justification 4 A robot trolley is controlled by a processor which takes input from a sensor following a black line on the floor, and makes decisions concerning steering to keep the trolley on the black line. The trolley would very soon leave the black line because it would not be steering quickly enough. The trolley would very soon leave the black line because it would not be steering quickly enough. Process control Next

1318/04/2015 Real-time Use & Justification 5 A catalogue shop processes orders by the code for a product being input and the system then comparing the code with information in its files. When it finds the correct code it can report to the user the number of that item that there are in the store. If there was only one left of a certain item, it would be necessary to record the fact that a shopper had bought it before the next shopper has their request dealt with otherwise the second person might be sold the same item. If there was only one left of a certain item, it would be necessary to record the fact that a shopper had bought it before the next shopper has their request dealt with otherwise the second person might be sold the same item. Because the information on the system must be processed immediately the O.S. needs to be ready to handle input as soon as it comes in. Because the information on the system must be processed immediately the O.S. needs to be ready to handle input as soon as it comes in. Transaction processing Back

1418/04/2015Plenary Define the terms On-line and Real-time processing:

1518/04/2015 Plenary On-Line User is able to communicate with processor directly Real-Time Data processed at time of input / input processed quickly enough to effect the next input.