CS Notes Archives - Coddicted

Socratic Touch…

Socratic Touch...
Who is Socrates? Socrates ( 469 BC – 399 BC) was a classical Greek Athenian philosopher.   Credited as one of thefounders of Western philosophy, he is an enigmatic figure known chiefly through the accounts of later classical writers, especially the writings of his students Plato and Xenophon, and the plays of his contemporary Aristophanes. ...

Wait-die and Wound-wait Schemes 8

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

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. ...

Mathematical Logic – Predicate Calculus

Statements involving variables such as:               x > 5 i.e. “x is greater than 5” are very common in Mathematics and in computer programs. Such a statement is neither ‘false’ nor ‘true’ unless the possible value for variable x is specified and hence it is not a proposition. Predicates and quantifiers ...

Context Switch

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

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

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

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 ...

Instruction codes

Instruction codes
The organization of the computer is defined by its internal registers, the timing and control structure and the set of instruction that it uses.The internal organization of a digital system is defined by the sequence of microoperations it performs on data stored in its registers The user of a computer can control the process by ...

The Havel Hakimi Algorithm 1

The Havel Hakimi Algorithm
The Havel Hakimi algorithm gives a systematic approach to answer the question of determining whether it is possible to construct a simple graph from a given degree sequence.   Take as input a degree sequence S and determine if that sequence is graphical That is, can we produce a graph with that degree sequence?   ...