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## Theory of Automata

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 ...

## The Havel Hakimi Algorithm1

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?   ...

## Tech Jargon

Words  Explanation  Context A context is the contents of a CPU’s registers and program counter at any point in time.  Process A process (also sometimes referred to as a task) is an executing/ running instance of a program.  Threads Threads are lightweight processes that can run in parallel and share an address space (i.e., a ...

## TCP Congestion control algorithm

Re-transmissions, Timeouts and Duplicate Acknowledgements TCP  is relegated to rely mostly upon implicit signals it learns from the network and remote host. TCP must make an educated guess as to the state of network and trust the information from the remote host in order to control the rate of data flow.   A sender’s implicit ...

## Spanning Trees

Let G = (V, E) be a connected graph in which each edge (u, v) E has an associated cost C(u, v).   A Spanning Tree for G is a subgraph of G that it is a free tree connecting all vertices in V. The cost of a spanning tree is the sum of costs on its edges.       Minimum Spanning Tree An MST of G is a spanning tree of G having a minimum cost. ...

## Serializability

Basic Assumption – Each transaction preserves database consistency Thus, serial execution of set of transactions preserves database consistency.   A (possibly concurrent) schedule is serializable if it os equivalent to serial schedule (say, Transaction T1 follows Transaction T2 or T2 follows T1)   Different form of schedule equivalence gives rise to the notions of  1. ...

Recoverability A recoverable schedule is one where, for each pair of Transaction Ti and Tj such that Tj  reads data item previously written by Ti   the commit operation of Ti  appears before the commit operation Tj .     Suppose that the system allows T9 to commit immediately after execution of read(A) instruction.Thus T9 commit before T8 does. Now suppose that T8 fails ...

## Normal Forms in Database

INF A relation is in first normal form if the domain of each attributes contains only atomic values and value of each attribute contains only a single value from that hand.   #Eliminate duplicative columns from the same table #Create separate table for each group of related data and identify each row with unique column(primary ...

## Kernel mode and User mode

Kernel mode In the kernel mode, the executing code has complete and unrestricted access to the underlying hardware. It can execute any CPU instruction and reference any memory address.Kernel mode is generally reserved for the lowest level, most trusted function of operating system.   User mode In user mode, the executing code has no ability ...

## Interrupts

An interrupt is a signal to the processor emitted by hardware or software indicating an occurrence of an event that needs immediate attention.The processor responds by suspending its current activities, saving its state, and executing a small program called an interrupt handler (or interrupt service routine, ISR) to deal with the event. This interruption is temporary, and after ...