How to unhide files in a folder

1. Enter into command prompt by clicking into Accessories->Command Prompt
2. Enter into select drive by typing the drive letter:
3. Then type "attrib -a -s -h -r /s /d /l" without semicolon.
4. Your problem is solved

How to find the IP or MAC address of a computer

Every computer has unique IP and MAC address. So let us know how to find the IP and MAC address of a computer.........

In Windows XP

1. Click on start
2. Click on run
3. Type cmd
4. Type ipconfig/all
5. IPv4 address gives the IP address of your computer
6. Physical address gives the MAC address of your computer

In Windows Vista/7/8

1. Click on start
2. Go to all programs
3. Click on accessories
4. Click on Command Prompt
5. Type ipconfig/all
6. IPv4 address gives the IP address of your computer
7. Physical address gives the MAC address of your computer

c programs asked in interviews

Recently I have goggled about programs asked in interview....and I found this website where both questions and answers were given

for c programs asked in interviews

there are several sites  1) click here 
                                  2) click here


For complete details on C visit here

How resistive Touch Screen Works??

A touch screen is an electronic visual display that can detect presence and location of touch within the display area...

It is a two dimensional sensing device that is made of two sheets of material separated by small spacers. There are three main touch screen technologies viz., resistive, capacitive and surface acoustic wave. Here i will discuss about resistive touch screen

Resistive touch screen:

The resistive touch screen consists of flexible top layer made of polythene and rigid bottom layer made of glass. Both the layers are spaced with spacers and are coated with indium tin oxide. When the screen is operating a small current flows in between the space. When a touch is made, the flexible screen presses down to touch the glass layer. A change in current is hence detected and coordinates of the point of touch calculated by the controller and parsed into readable signal for the operating system to react accordingly.

The four-wire resistive touch screen uses both the layers to calculate the axes information of the touch. Touch measurement is a two-step process. The x-coordinate of the touch point is calculated by creating a voltage gradient on flexible layer, and the y-coordinate is determined by creating a voltage gradient along  the bottom layer. 

Shortcuts in solving aptitude-10

SIMPLE INTEREST COMPOUND INTEREST

Interest

Interest is the ‘extra’ money paid by the borrower to the lender for using the money for a specified

period of time.

Principal (P) : - The money lent or borrowed is called the Principal.

Amount (A) : - The total money, i.e. Principal + Interest is called the amount.

Rate of interest (r) :- The rate at which interest is calculated on the Principal is called the rate of interest.

Interest is of two kinds

1.    Simple interest (I)

If the interest is calculated for every time period (generally calculated yearly, half-yearly, quarter-yearly) only on the original sum (Principal) borrowed, then such interest is called as the simple interest.

The interest is same for each qf the time-periods.

i.e. if the interest for one time-period (if taken as a year) is I, then the interest for ‘n’ time-periods(years) is ‘nI’ 

2.    Compound interest

In this method, at the end of each time period, the interest is added to the principal, and this amount becomes the new Principal for/the next time period. The amount at the end of the second time period becomes the Principal for the third time period and so on.

The interest is not same for all the time-periods, but the interest for any time period is greater than the interest for the preceeding time-period. Compound interest (CI) = Final amount  -  initial principal

To Exercise some more problems on SI and CI visit here

Shortcuts in solving aptitude-9

NUMBERS

Natural numbers

The set of counting numbers 1, 2, 3, 4, …………are called as the natural numbers, denoted by N.

N = {1, 2, 3, ...}

Whole numbers

The set of natural numbers together with the number ‘0’ is known as the set of whole numbers, denoted by W.

W= {0, 1,2,3, ...)

Integers

The negative whole numbers, the number '0' and the natural numbers together form the set of Integers, denoted by Z.

Z= {... ­­-3, -2,– 1, 0, 1.2.3, …..}

Rational numbers

Numbers which can be written in the form p/q where p and q are integers and q ≠0 are called as rational numbers, denoted by Q.

Decimal representation of rational numbers

  v  If a fraction (rational number) in its lowest terms has no other prime factors except 2 and 5. we get a terminating decimal. 

    

     Irrational numbers

The numbers, which cannot be expressed as rational numbers is called as an irrational number.

Note:

Every non-terminating, non-recurring decimal is an irrational number.

Note :

A number may he a rational number or an irrational number, but! it cannot be both.

Real numbers

The set of all numbers comprising rational numbers and irrational numbers is known as the set of real numbers, denoted by R.

Note :

  v  On the number line, there is a point corresponding to every real number and to every point on the number line, there is a real number. Hence the number line is called the Real Number line.

  v  Real numbers are so called because they can be seen as points representing them on the number line.

Complex numbers

There is no real number, whose square is a negative number.

E.g. is not a real number.

Such numbers are called as imaginary numbers.

The set of numbers comprising of real numbers and imaginary numbers is known as the set of complex numbers, denoted by C.

The ordered pair (a, b) where a and b are real numbers, when expressed in the form a + ib, is called a complex number.

a is called the real part, and b is called the imaginary part.

Note:

  v  Every real number a can be represented as a complex number, (a, 0).

  v  The complex numbers a + ib and a - ib are called conjugate complex numbers. Each is called the conjugate of the other.

  v  The sum and product of two conjugate complex numbers are real.

  v  Every complex number can be represented as a point in the coordinate plane, by taking real part on the x-axis and the imaginary part on the y-axis.

Hence, x axis is called real axis

y-axis called imaginary axis.

Some of Mathematical formula are unable to mention here...so for more visit here

Shortcuts in solving aptitude-8

Permutations and Combinations

Formulae:

         

Factorial Notation:

Let n be positive integer. Then ,factorial n denoted by n!

is defined as n! = n(n-1)(n-2). . . .  . . .  .3.2.1

Permutations:

The different arrangements of a given number of things by

taking some or all at a time, are called permutations.

e.g.:- All permutations( or arrangements)made with the letters

a,b,c by taking two at a time are (ab,ba,ac,ca,bc,cb)

Numbers of permutations:

Number of all permutations of n things, taken r at a time is

given by  nPr  = n(n-1)(n-2). .  .. . . (n-r+1)

               = n! / (n-r)!

An Important Result:

If there are n objects of which p1 are alike of one kind;

p2 are alike of another kind ; p3 are alike of third kind and

so on and pr  are alike of rth kind, such that

(p1+p2+. . . . . . . . pr) = n

Then, number of permutations of these n objects is:

      n! / (p1!).(p2!). . . . .(pr!)

Combinations:

Each of different groups or selections which can be formed by

taking some or all of a number of objects, is called a combination.

  e.g.:- Suppose we want to select two out of three boys A,B,C .

         then ,possible selection are AB,BC & CA.

      Note that AB and BA represent the same selection.

Number of Combination:

The number of all combination of n things taken r at a time is:

    nCr = n! / (r!)(n-r)!

         = n(n-1)(n-2). . . . . . . tor factors / r!

Note: nCn = 1 and nC0 =1

An Important Result:

 nCr = nC(n-r)

    

             To exercise problems regarding permutations & combinations visit here

Probability

Introduction:

Experiment:

An operation which can produce some well-defined outcome is called an experiment.

Random Experiment:

An experiment in which all possible out comes are known and the exact output cannot be predicted in advance is called a random experiment. EX:

1) Rolling an unbiased dice.

2) Tossing a fair coin.

3) Drawing a card from a pack of well-shuffled cards .

4)Picking up a ball of certain color from a bag containing balls of different colors.

Details:

1) When we thrown a coin ,then either a Head(H) or a Tail(T)appears.

2)A dice is a solid cube ,having 6 faces, marked 1,2,3,4,5,6respectively. When we throw a die ,the outcome is the number that appears on its upper face.

3)A pack of cards has 52 cards.

It has 13 cards of each suit, namely spades, clubs, hearts and diamonds.

 Cards of spades and clubs are black cards.

Cards of hearts and diamonds are red cards.

There are four honors of each suit.

These are Aces, Kings, queens and Jacks.

These are called Face cards.

Sample Space:

When we perform an experiment ,then the set of S of all possible outcomes is called the Sample space .

Event: Any subset of a sample space is called an Event.

Probability of occurrence of an Event:

Let S be the sample space.

Let E be the Event.

Then E c S i.e. E is subset of S then

probability of E  p(E) =n(E)/n(S).

Results on Probability:

1)P(S) =1.

2)0 < P(E) < 1

probability of an event lies between 0 and 1.

Max value of probability of an event is one.

3)For any events A and B we have .

P(AUB) =P(A) +P(B) -P(A n B ).

4)If A denotes (not -A) then

  P (A) =1-P(A)

  P(A)+P(A) =1.

To Exercise problems in probability visit here 

Shortcuts in solving aptitude-7

Allegation or Mixtures

Important Facts and Formulae:

1. Allegation: It is the rule that enables us to find the Ratio in which two of more ingredients at the given price must be mixed to produce a mixture of a desired price.

2. Mean Price: The cost price of a unit quantity of the mixture is called the mean price.

3. Rule of Allegation: If two ingredients are mixed then

Quantity of Cheaper / Quantity of Dearer = (C.P of Dearer – Mean Price) /(Mean Price–C.P of Cheaper).

C.P of a unit quantity of cheaper(c)    C.P of unit quantity of dearer (d)

                                                  Mean Price (m)

                                 (d-m)                                               (m-c)

        Cheaper quantity: Dearer quantity = (d-m):(m-c)

4. Suppose a container contains x units of liquid from which units are taken out and replaced by water. After n Operatations the quantity of pure liquid = x (1 – y/x)n units.

To exercise some problems on allegation or mixtures visit here

Boats and Streams

Important facts:  

1)In water, the direction along the stream is called downstream.

2)Direction against the stream is called upstream.

3)The speed of boat in still water is U km/hr and the speed of

stream is V km/hr then

speed downstream =U + V km/hr

speed up stream = U – V km/hr

Formulae:

If the speed downstream is A km/hr and the speed up stream is

B km/hr then speed in still water = ½(A+B) km/hr

rate of stream =1/2(A-B) km/hr

To exercise some problems on Boats and streams visit here

Shortcuts in solving aptitude-6

TRAINS

General Concept:

(1) Time taken by a train x mt long in passing a signal poster a pole or a standing man = time taken by   the train to cover x mt

(2) Time taken by a train x mt long in passing a stationary object of length y mt = time taken by the train to cover x+y mt

(3) Suppose two trains or two bodies are moving in the same direction at u kmph and v kmph such that u > v then their relative speed is u-v kmph

(4)If two trains of length x km and y km are moving in opposite directions at u kmph and vmph,then time taken by the train to cross each other = (x+y)/(u+v) hr

(5) Suppose two trains or two bodies are moving in opposite direction at u kmph and v kmph then, their relative speed = (u+v) kmph

(6)If two train start at the same time from 2 points A & B towards each other and after crossing they take a & b hours in reaching B & A respectively then A's speed : B's speed = (b^1/2 :   a^1/2 )

To exercise some problems on trains visit here

RACES AND GAMES OF SKILLS

Races:

A contest of speed in running, riding, driving, sailing or rowing is called a Race

Race Course:

The ground or path on which contests are made is called a  race course

Starting Point:

The point from which a race begins is called starting point.

Winning point or goal:

The point set to bound a race is called a winning point.

Dead Heat Race:

If all the persons contesting a race reach the goal exactly at the same time, then the race is called a dead heat race.

Start:

Suppose A and B are two contestants in a race .If before the start of the race, A is at the starting point and B is ahead of A by 12 meters. Then we say that "A gives B a start 12 meters.

->To cover a race of 100metres in this case, A will have to cover 100m while B will have to cover 88m=(100-12)

->In a100m race 'A can give B 12m' or 'A can give B a start of 12m' or 'A beats B by 12m'means that while A runs 100m B runs 88m.

Games:

A game of 100m, means that the person among the contestants who Scores 100 points first is the winner.

If A scores 100 points while B scores only 80 points then we say That 'A can give B 20 points'.

To exercise some problems on races visit here

Shortcuts in solving aptitude-5

TIME AND WORK

Introduction:

In any business effort it is very important to be good as well as clever at calculating the number of people required to delegate to a piece of work so that the work can be completed in a stipulated time.  The following are some of the basic aspects related to TIME and WORK.

Work done is usually considered as one unit.  Time taken to do the work depends on various factors such as the number of Persons’ doing the work, their efficiency ‘in doing the work’, ‘amount of work they bear’, ‘number of days they take’ and time they spend per day. In case, there is more than one person carrying out the work, it is assumed that each person does the same amount of work each day.

Some of mathmetical folmulae are unable to mention here. so kindly visit here

Work and Wages

Introduction:

At Certain times people show little interest in calculating expenditure on petty things such as spending money for a servant maid or for the repair of a tank, pipe or a cistern. But this is a very serious issue for organizations to reduce their expenditure.  Hence they calculate as follows.

          Wages earned by people by doing some work together are to be distributed in the ratio of the total work done by each of them.  If a group of people work at different places and if the work done by each of them per day is different then the wages of earnings have to be divided in the ratio of the work per day to each of them.

          i.e., if ‘A’ can do a piece of work in ‘x’ days and ‘B’ in ‘y’ days, then the wages are to be distributed in the ratio of 1/x : 1/y, If three men can do a task in x,y and z days respectively then the wages are to be distributed in the ratio of 1/x:1/y:1/z.

Some of mathmetical folmulae are unable to mention here. so kindly visit here

T

Shortcuts in solving aptitude-4

PROFIT AND LOSS

Cost Price (C.P.) = Cost price of an article is the price at which the article is purchased.

Selling Price (S.P.) = Selling price of an article is the price at which the article is sold.

Profit or Gain = Selling Price – Cost Price – S.P. – C.P.

Marked Price (M. P.) or List Price or Catalogue Price

Marked price is the price that is marked or fixed on the product, by the manufacturers.

These products are sold to the wholesale dealers reducing these prices by some percentage. This reduction in the price is called 'Trade discount'.

Selling Price = Marked Price – discount

                  = M. P. – d (where d is the discount)

Some of mathmetical folmulae are unable to mention here. so kindly visit here

COMPOUND INTEREST

Important Facts and Formulae:

Compound Interest:

Sometimes it so happens that the borrower and the lender gree to fix up a certain unit of time ,say yearly or half-yearly or quarterly to settle the previous account.In such cases ,the amount after the first unit of time becomes the principal for the 2nd unit ,the amount after

second unit becomes the principal for the 3rd unit and soon. After a specified period ,the difference between the amount and the money borrowed is called Compound Interest

for that period.

Formulae:

Let principal=p,Rate=R% per annum Time=nyears

1.When interest is compounded Annually,Amount=P[1+(R/100)]n

2.When interest is compounded Halfyearly,Amount=P[1+((R/2)100)]2n

3.When interest is compounded Quaterly, Amount=P[1+((R/4)100)]4n

4.When interest is compounded Annually,but time in fractionssay 3 2/5 yrs Amount=P[1+(R/100)]3[1+((2R/5)/100)]

5.When rates are different for different years R1%,R2%,R3%for 1st ,2nd ,3rd yrs respectivelyAmount=P[1+(R1/100)][1+(R2/100)][1+(R3/100)]

6.Present Worth of Rs.X due n years hence is given by Present Worth=X/[1+(R/100)]n

For problems regarding Compound Interest Click here

Shortcuts in solving aptitude-3

PARTNERSHIPS

PATNERSHIP

When two or more persons agree to run a business jointly by pooling in their investments (capitals), they are called partners and the deal is called partnership. There are two kinds of partnerships.

i.          Simple partnership.

ii.          Compound partnership.

Simple Partnership

If the investments of the partners are for the same period of the time, then the partnership is called simple partnership.

In this partnership, the profit or loss is divided in the ratio of their respective investments.

Compound Partnership
If the investments of the partners are for different periods of time, the partnership is called compound partnership. In this partnership, the profit or loss is divided in the ratio of the product of the investment and time-period of investment.

Some of mathmetical folmulae are unable to mention here. so kindly visit here

PERCENTAGES

Percentage (%)

Percent means for every hundred.

Percentage is a fraction whose denominator is 100. and the numerator of the fraction is called rate percent.

Converting fractions or decimals to percentages

To convert a fraction or a decimal to a percentage, multiply the fraction with 100.

Converting percentages to fractions

To convert percentages to fractions or decimals, divide the percentage by 100.

Some of mathmetical folmulae are unable to mention here. so kindly visit here

Shortcuts in solving aptitude-2

AVERAGE

Formulae:

1.Average=Sum of quantities/Number of quantities.

2.Suppose a man covers a certain distance at x kmph and an equal distance at y kmph, then the average speed during the whole journey is (2xy/x+y) kmph.

To solve problems regarding average....click here

RATIO AND PROPORTION

Ratio

Ratio is a comparison of two quantities of the same kind.

It shows the number of times one quantity contains another quantity.

The ratio of two quantities is equivalent to the fraction that one quantity is of the other.

The ratio of "a" to "b" is written as a: b, read as "a is to b\ and is equal to a/b.

In the ratio a: b, 'a' and 'b" are called the terms of the ratio.

‘a’ is called the first term (antecedent) and ^Lb" is called the second term (consequent).

Note: –

o    The ratio is an abstract number.

To solve problems regarding ratio and proportion....click here

Shortcut methods in aptitude solving-1

Time and Distance problems

1. Average Speed=Total distance/Total time

• When they are more than one average speed then in order to find the average speeds of all here are some conditions

1. When time is constant Average speed is Average of all speeds.
2. When distance is constant then average speed is Harmonic mean of all average speeds.

For e.g: Two speeds s₁,s₂ Average speed=2/((1/s1)+(1/s2))

Train Problems:

A train of length ‘l’ speed ‘s’ crossing a pole(man) of negligible length then time taken by train to train is

T=l/s

2    A train of length ‘l’ and speed ‘s’ crossing a platform of length ‘l_p’, then time taken by train to cross platform is
                                                                  T=(l+lp)/s

Relative speed Problems:

            In solving Relative speed problems there arises two cases

Case 1: When two objects of speeds s1, s2 are moving in the same direction then relative speed is difference of their speeds (i.e., s1~s2)

Case 2: When two objects of speeds s1, s2 are moving in the opposite direction then relative speed is sum of their speeds (i.e., s1+s2) 

To remember more things constant repetition is a way. The mind only remembers a quarter of what you hear.