# 2.3 Pointers and arrays  (Page 3/8)

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## Pointer assignment

Since pointers are variables, they can be used without dereferencing. Pointer assignment between two pointers makes them point to the same pointee. So the assignment `iq = ip;` copies the contents of ip into iq, thus making iq point to whatever ip pointed to. It makes iq point to the same pointee as ip. Pointer assignment does not touch the pointees. It just changes one pointer to have the same reference as another pointer. After pointer assignment, the two pointers are said to be "sharing" the pointee.

Example Consider the following programs:

```main() {int i = 3, j = 6; int *p1, *p2;p1 =&i; p2 =&j; *p1 = *p2;} andmain() {int i = 3, j = 6; int *p1, *p2;p1 =&i; p2 =&j; p1 = p2;}```

Suppose the values of variables before executing the last assignment are

i FFEC 3
j FFEE 6
p1 FFDA FFEC
p2 FFDC FFEE

After the assignment *p1 = *p2; for the first program:

i FFEC 6
j FFEE 6
p1 FFDA FFEC
p2 FFDC FFEE

While the assignment p1 = p2 for the second program results

i FFEC 3
j FFEE 6
p1 FFDA FFEE
p2 FFDC FFEE

## Initializing pointers

Pointer variables with automatic storage duration start with an undefined value, unless their declaration contains an explicit initializer. You can initialize a pointer with the following kinds of initializers:

• A null pointer constant.
• A pointer to the same type, or to a less qualified version of the same type.
• A void pointer, if the pointer being initialized is not a function pointer. Here again, the pointer being initialized can be a pointer to a more qualified type.

## Operators on pointers

Besides using assignments to make a pointer refer to a given object or function, you can also modify an object pointer using arithmetic operations. When you perform pointer arithmetic , the compiler automatically adapts the operation to the size of the objects referred to by the pointer type.

You can perform the following operations on pointers to objects:

• Adding an integer to, or subtracting an integer from, a pointer.
• Subtracting one pointer from another.
• Comparing two pointers.

If ip points to the integer x, then *ip can occur in any context where x could, so

`*ip = *ip + 10;`

The unary operators * and&bind more tightly than arithmetic operators, so the assignment

`y = *ip + 1`

takes whatever ip points at, adds 1, and assigns the result to y, while

`*ip += 1`

increments what ip points to, as do

`++*ip`

and

`(*ip)++`

The parentheses are necessary in this last example; without them, the expression would increment ip instead of what it points to, because unary operators like * and ++ associate right to left.

When you subtract one pointer from another, the two pointers must have the same basic type, although you can disregard any type. Furthermore, you may compare any pointer with a null pointer constant using the equality operators (== and !=), and you may compare any object pointer with a pointer to void.

## Pointer to pointer

A pointer variable is itself an object in memory, which means that a pointer can point to it. To declare a pointer to a pointer , you must use two asterisks, as in the following Example

find the 15th term of the geometric sequince whose first is 18 and last term of 387
I know this work
salma
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
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
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Sherica
im all ears I need to learn
Sherica
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Uday
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salma
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or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
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China
Cied
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
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what is system testing
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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
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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
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