# 2.3 Pointers and arrays  (Page 2/8)

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`iPtr =&iVar; // Let iPtr point to the variable iVar.`

In a pointer declaration, the asterisk (*) is part of an individual declarator. We can thus define and initialize the variables iVar and iPtr in one declaration, as follows:

```int iVar = 77, *iPtr =&iVar; // Define an int variable and a // pointer to it.```

The second of these two declarations initializes the pointer iPtr with the address of the variable iVar, so that iPtr points to iVar. Figure 4.1. illustrates one possible arrangement of the variables iVar and iPtr in memory. The addresses shown are purely fictitious examples. As Figure 4.1. shows, the value stored in the pointer iPtr is the address of the object iVar.

It is often useful to output addresses for verification and debugging purposes. The printf() functions provide a format specifier for pointers: %p. The following statement prints the address and contents of the variable iPtr:

```printf("Value of iPtr (i.e. the address of iVar): %p\n" "Address of iPtr: %p\n", iPtr,&iPtr);```

The size of a pointer in memory given by the expression sizeof(iPtr)

## &And * operators

The unary operator&gives the address of an object, so the statement

`p =&c;`

assigns the address of c to the variable p, and p is said to “point to” c. The&operator only applies to objects in memory: variables and array elements. It cannot be applied to expressions, constants, or register variables.

* is the operator that retrieves the value stored at the address held in the pointer. The indirection operator * yields the location in memory whose address is stored in a pointer. If ptr is a pointer, then *ptr designates the object that ptr points to. Using the indirection operator is sometimes called dereferencing a pointer. The type of the pointer determines the type of object that is assumed to be at that location in memory. For example, when you access a given location using an int pointer, you read or write an object of type int.

The indirection operator * is a unary operator; that is, it has only one operand.ptr points to the variable x. Hence the expression *ptr is equivalent to the variable x itself.

```double x, y, *ptr; // Two double variables and a pointer to double. ptr =&x; // Let ptr point to x. *ptr = 7.8; // Assign the value 7.8 to the variable x.*ptr *= 2.5; // Multiply x by 2.5. y = *ptr + 0.5; // Assign y the result of the addition x + 0.5.```

Do not confuse the asterisk (*) in a pointer declaration with the indirection operator. The syntax of the declaration can be seen as an illustration of how to use the pointer.

`double *ptr;`

As declared here, ptr has the type double * (read: "pointer to double"). Hence the expression *ptr would have the type double.

Of course, the indirection operator * must be used with only a pointer that contains a valid address. This usage requires careful programming! Without the assignment ptr =&x in the listing above, all of the statements containing *ptr would be senseless dereferencing an undefined pointer value and might well cause the program to crash.

find the 15th term of the geometric sequince whose first is 18 and last term of 387
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
can someone help me with some logarithmic and exponential equations.
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
how do you translate this in Algebraic Expressions
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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