REAL TIME OPERATING SYSTEM

REAL TIME SYSTEM: 

REAL TIME SYSTEM SUBMITED BY-MADHURYA VARSHNEY ROLL NO-0822510053

CONTENTS: 

CONTENTS WHAT IS REAL TIME SYSTEM ? TYPES OF REAL TIME SYSTEM . WHAT IS REAL TIME OPERATING SYSTEM? RTOS ARCHITECTURE. DESIGN OF RTOS. SCHEDULING ALGORITHIMS OF RTOS. MEMORY ALLOCATION. EXAMPLE.

WHAT IS REAL TIME SYSTEM ?: 

WHAT IS REAL TIME SYSTEM ? IN COMPUTER SCIENCE , REAL TIME SYSTEM DERIVED FROM REAL TIME COMPUTING DEFINED AS THE STUDY OF HARDWARE AND SOFTWARE SYSTEM THAT ARE SUBJECTED TO REAL TIME CONSTRAINTS. THE NEED OF REAL TIME SYSTEM ARE OFTEN EXPRESSED IN CONTEXT OF REAL TIME OPERATING SYSTEM(RTOS) BECAUSE IT PROVIDE FRAMEWORK TO DEVLOP REAL TIME APPLICATION SOFTWARE.

TYPES OF REAL TIME SYSTEM: 

TYPES OF REAL TIME SYSTEM 1- HARD REAL TIME SYSTEM 1.1- IT ENSURES THAT A TASK SHOULD COMPLETE ON TIME 1.2- A HARD REAL TIME SYSTEM HAS STRICT DEADLINES TO COMPLETE THE TASK 1.3- IF A REAL TIME SYSTEM CRASHES IT MAY CAUSE GREAT DAMAGE TO THE SYSTEM EXAMPLE-CAR ENGINE SYSTEM , EMBEDDED SYSTEM , MEDICAL SYSTEM SUCH AS HEART PACEMAKER

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2- SOFT REAL TIME SYSTEM 2.1-IT HAS TOLRENCE WITH RESPECT TO TIME 2.2-IT MAY RESULT IN DEGRADED QUALITY EXAMPLE-OMITTING FLAMES WHILE DISPLAYING A VEDIO,FLIGHT CONTROL SYSTEMS (SOFTWARE THAT DEVLOP FLIGHT SCHEDULE FAR COMERCIAL AIRLINES)

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3-FIRM REAL TIME SYSTEM MISSING DEADLINE REQUIRMENT CAUSE UNEXPECTED QUALITY REDUCTION 4-NON REAL TIME SYSTEM NO DEADLINE HAS TO MEET

WHAT IS A REAL TIME OPERATING SYSTEM?: 

WHAT IS A REAL TIME OPERATING SYSTEM? A REAL TIME OPERATING SYSTEM IS AN OPERATING SYSTEM THAT SERVES REAL TIME APPLICATION IT IS COSISTENT ABOUT THE AMOUNT OF TIME IT TAKES TO ACCEPT AND COMPLETE A APPLICATION A RTOS IS MORE FREQUENTLY DEDICATED FOR NARROW SET APPLICATION A RTOS IS MOST VALUED FOR HOW QUICKLY IT RESPOND ON A APPLICATION WITH IN GIVEN PERIOD OF TIME

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RTOS: Target Architectures Processors MIPS (MICROPROCESSOR WITHOUT INTERLOCKED PIPELINED STAGES) Microcontrollers ~20 ARM7 100-133 ARM9 180-250 Strong ARM 206 Intel Xscale 400 Mips4Kcore 400 X86

DESIGN OF RTOS: 

DESIGN OF RTOS IN TYPICAL DESIGN , A TASK HAS FOLLOWING STAGES I-RUNNING(EXECUTED ON CPU) 2-READY(READY TO BE EXECUTED) 3-BLOCKED(WAITING FOR INPUT/OUTPUT)

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MOST TASK ARE BLOCKED OR READY MOST OF THE TIME BECASE CPU IS BUSY IN EXECUTING ONE TASK IN SCHEDULING MORE INFORMATION ABOUT THE TASK ARE KNOWN- 1-NO OF TASK 2-REQUIRMENT OF RESOURCES 3-REALIZE TIME 4-EXECUTION TIME 5-DEADLINES A BETTER DETERMINISTIC CAN BE SCHEDULED BETTER

SCHEDULING ALGORITHIMS IN RTOS: 

SCHEDULING ALGORITHIMS IN RTOS THE MOST COMMON SCHEDULING ALGORITHIMS ARE 1-PRIORITY SCHEDULING-EVENT DRIVEN WHICH SWITCH TASK WHEN A TASK OF HIGHER PRIORITY IS ENCOUNTERED 2-ROUND ROBIN- IT IS ALSO TREATED AS TIME SHARING . IT SWITCHES TASK AFTER A GIVEN CLOCK INTERUPTION IN EARLIER OS PRIORITY SCHEDULING IS USED TO MINIMIZE SCHEDULING TIME WITHOUT SWITCHING NO. OF PROCESS

PROPERTIES OF SCHEDULING ALGORITHMS: 

PROPERTIES OF SCHEDULING ALGORITHMS 1-PRIORITY SCHEDULING-ALSO KNOWN AS GREEDY/EVENT DRIVEN/LIST 1.1-PROCESSOR NEVER LEFT IDLE 1.2-PROCESSES ARE ARRANGED ACCORDING TO PRIORITY 1.3-THIS ALGORITHIM HAVE A DISADVANTAGE OF STARVATION

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2- ROUND ROBIN SCHEDULING 2.1 –JOBS ARE ARRANGED FIFO MANNER 2.2-A TIME QUANTUM IS ASSIGNED FOR SWITCHING AFTER EVERY PROCESS 2.3-NO STARVATION OF A PROCESSES EXAMPLE- HIGH SPEED SWITCHING NETWORK

OTHER SCHEDULING ALGO’S: 

OTHER SCHEDULING ALGO’S 1- EARLIEST DEADLINE FIRST-THE PROCESS WITH THE EARLIEST DEADLINE CA BE ASSIGNED PROCESSOR FIRST 2- RATE MONOTONIC SCHEDULING- IN THIS SCHEDULING THE PROCESS WITH THE SHORTEST EXECUTION TIME IS EXECUTED FIRST 3-STOCHASTIC SCHEDULING-STOSHASTIC IS A GREEK WORD WHICH MEANS RANDOM. IN STOCHASTIC SCHEDULING IS NON DETERMINISTIC ,IT CAN START ANY PROCESS FIRST

MEMORY ALLOCATION: 

MEMORY ALLOCATION MEMORY ALLOCATION IN RTOS IS MORE CRITICAL THAN IN ANY OTHER OPERATING SYSTEM. SPEED OF ALLOCATION IS IMPORTANT A STANDARD MEMORY ALLOCATION SCHEME SCANS THE LINKED LIST OF INTERMEDIATE LENGTH TO FIND A SUITABLE FREE MEMORY BLOCK. THIS IS UNEXPECTABLE IN RTOS SINCE MEMORY ALLOCATION HAS TO OCCUR WITH IN CERTAIN AMOUNT OF TIME

EXAMPLE-: 

EXAMPLE- AN EARLY EXAMPLE OF LARGE SCALE RTOS WAS “TRANSACTION PROCESSING FACILITY” DEVLOPED BY AMERICAN AIRLINES AND IBM FOR THE “SABRE AIRLINE RESERVATION SYSTEM” BEST KNOWN EXAMPLE ARE- QNX WINDOWS CE OSE

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QUERIES

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