Computer engineering Archives

Wait-die and Wound-wait Schemes 11

Apr

18

2013

Wait-die scheme: It is a non-preemptive technique for deadlock prevention. When transaction Ti requests a data item currently held by Tj, Ti is allowed to wait only if it has a timestamp smaller than that of Tj (That is Ti is older than Tj), otherwise Ti is rolled back (dies) For example: Suppose that transaction T22, T23, T24 have time-stamps 5, 10 and ...

Validation Based Protocol

Apr

18

2013

It imposes less overhead Also based on Timestamp Protocol. It has three phases: Read Phase: During this phase, the system executes transaction Ti. . It reads the values of the various data items and stores them in variable local to Ti. It performs all the write operations on temporary local variables without update of the actual database. ...

Context Switch

Apr

18

2013

A context switch (sometimes, process switch or a task switch) is the switching of the CPU from one process or thread to another.It is sometimes described as the kernel suspending execution of one process on the CPU and resuming execution of some other process that had previously been suspended. Context switching can be described ...

Locality of Reference

Apr

17

2013

Analysis of a large number of typical program has shown that the references to memory at any given interval of time tend to be confined within a few localized areas in memory. This is phenomenon is known as the property of locality of reference. Over short interval of time, the addresses generated ...

Processes and Threads

Apr

10

2013

Processes A processes is the “heaviest” unit of kernel scheduling. Processes own resources allocated by the operating system. Resources include a. memory b. file handler c. sockets d. device handler e. windows Processes do not share address space or file resources except through explicit methods such as inheriting file handles or shared memory segments or ...

Hardwired control and Micro-programmed control

Apr

10

2013

There are two major types of control organization – Hardwired control and micro-programmed control. S.No. Hardwired Control Micro-programmed Control 1. The control logic is implemented with gates, flip-flops, decoders. It can be optimized to produce fast mode of operation. The control information is stored in control memory. The control memory is ...

Decidability of Languages 6

Apr

4

2013

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Closure Properties of Languages

Apr

4

2013

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Types of Delays

Apr

4

2013

Types of Delays 1. Nodal processing delay 2. Queuing delay 3. Transmission delay 4. Propagation delay (1-2)Processing delay a. The time required to examine the packets header and determine where to direct the packet. b. Other factors include, the time needed to check for bit level errors in the packet that occurred in transmitting the ...

Theory of Automata

Apr

4

2013

Definition of Automaton: An Automaton is a “self-acting” system that operates on a set of input symbols (one at a time) and decides whether or not to accept the given input sequence. Sometimes it may optionally produce some output sequence as well. Formally an Automaton may be defined to consist of the following: 1. Input: A ...