## Types of Keys in Relational Model (Candidate, Super, Primary, Alternate and Foreign)

We strongly recommend to refer below post as a prerequisite of this. DBMS | Relational Model Introduction and Codd Rules Different Types of Keys in… Read More »

## Data Abstraction and Data Independence

Database systems comprise of complex data-structures. In order to make the system efficient in terms of retrieval of data, and reduce complexity in terms of… Read More »

## DBMS Architecture 2-Level, 3-Level

Two tier architecture: Two tier architecture is similar to a basic client-server model. The application at the client end directly communicates with the database at… Read More »

## GATE 2017 Important dates and links

GATE 2017 Online Examination Dates: February 4 – 5, 2017 & February 11 – 12, 2017  (Saturdays and Sundays only). GATE CS exam is on 11th… Read More »

## Undecidability and Reducibility

Decidable Problems A problem is decidable if we can construct a Turing machine which will halt in finite amount of time for every input… Read More »

## Mealy and Moore Machines

Moore Machines: Moore machines are finite state machines with output value and its output depends only on present state. It can be defined as (Q, q0, ∑, O, δ, λ) where: Q is finite set of states. q0 is the initial state. ∑ is the input alphabet. O is the output alphabet. δ is transition function which maps Q×∑ → Q. λ is the output function which maps Q → O. Figure 1 In the moore machine shown in Figure 1, the output is represented with each input state separated by /. The length of output for a moore machine is greater than input by 1. Input: 11 Transition: δ (q0,11)=> δ(q2,1)=>q2 Output: 000 (0 for q0, 0 for q2 and again 0 for q2)  Mealy Machines: Mealy machines are also finite state machines with output value and its output depends on present state and current input symbol. It can be defined as (Q, q0, ∑, O, δ, λ’) where: Q is finite set of states. q0 is the initial state. ∑ is the input alphabet. O is the output alphabet. δ is transition function which maps Q×∑ → Q. ‘λ’ is the output function which maps Q×∑→ O. Figure… Read More »

## Caesar Cipher in Cryptography

The Caesar Cipher technique is one of the earliest and simplest method of encryption technique. It’s simply a type of substitution cipher, i.e., each letter… Read More »

## Mathematics | The Pigeonhole Principle

Suppose that a flock of 20 pigeons flies into a set of 19 pigeonholes to roost. Because there are 20 pigeons but only 19 pigeonholes,… Read More »

## Regular Expressions, Regular Grammar and Regular Languages

As discussed in Chomsky Hierarchy, Regular Languages are the most restricted types of languages and are accepted by finite automata.   Regular Expressions Regular Expressions… Read More »

## TOC | Designing Finite Automata from Regular Expression (Set 1)

In this article, we will see some popular regular expressions and how we can convert them to finite automata. Even number of a’s : The… Read More »

## Mathematics | Lagrange’s Mean Value Theorem

Suppose be a function satisfying three conditions: 1) f(x) is continuous in the closed interval a ≤ x ≤ b 2) f(x) is differentiable in… Read More »

## Mathematics | Rolle’s Mean Value Theorem

Suppose f(x) be a function satisfying three conditions: 1) f(x) is continuous in the closed interval a ≤ x ≤ b 2) f(x) is differentiable… Read More »

## Mathematics | Eigen Values and Eigen Vectors

Eigen vector of a matrix A is a vector represented by a matrix X such that when X is multiplied with matrix A, then the… Read More »

## Segmentation in Operating System

A process is divided into Segments. The chunks that a program is divided into which are not necessarily all of the same sizes are called… Read More »