CS Notes Archives - Coddicted

Lossless Dependency Preserving 3NF decomposition Algorithm 1

The minimal cover of F is given 1. Search for dependencies in F-having the same attribute set on the left hand side A: A->B1, A->B2, A->B3, …, A->Bk And construct relation as (A, B1, B2, B3,…, Bk) 2. Construct a relation with remainder attributes. 3. In case none of the relations has a candidate key, ...

Recommended books for GATE (Computer Science)

Recommended books for GATE (Computer Science)
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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 – Well Formed Formulas

A propositional variable is similar to any real variable you see in mathematics. For example xis a variable that can take any mathematical value. Similarly, a propositional variable, say P, can take any proposition as a value. The proposition as a value is called a propositional constant. Definition: WFFs produce a proposition.  To construct a WFF ...

Mathematical Logic – Translation

Translating English sentences into propositional forms We take an example to explain the procedure: Example: Convert the following sentence into propositional form:                 “If I earn more than 2Lac Rupees then I must file income tax return”. 1.  Identify the basic simple sentences and denote them with some variables.        In the above ...

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 ...