Very Basic Questions

[zealiff]

Hi all. I have a VERY basic question regarding parenthesis.

1. What does the parenthesis mean after variables? For Example:

Code: Select all

int Main()

or

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void Something (void)

I don't understand when and why you need these. Also, for the above line of code, why do you need void inside the ().

[Alvaro]

I'm assuming you are trying to learn C++.

Hi all. I have a VERY basic question regarding parenthesis.

1. What does the parenthesis mean after variables? For Example:

Code: Select all

int Main()

or

Code: Select all

void Something (void)

I don't understand when and why you need these.

http://www.cplusplus.com/doc/tutorial/functions/

Also, for the above line of code, why do you need void inside the ().

In C++ you don't.

[zealiff]

Ok next question. This is about Pointers.

If you have this:

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andy = 25;        // andy == 25
ted = &andy;    // ted == memory address
beth = *ted;     // beth == 25


Why would you need to get the memory address? Please don't point me to a website, give me the kindergarden answer.

Thanks

[Alvaro]

The code would be easier to understand if you declare the types of the variables you use. And I don't understand the question.

[zealiff]

It's just an example.

Again, why would you need to get the address of a variable stored in memory?

If you scratching your head, please re-read the title of this thread...

[Alvaro]

For instance, you may want to have a function that changes the value of your variable.

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#include <iostream>

void add_five(int *x) {
  *x += 5;
}

int main() {
  int i=0;
  add_five(&i);
  std::cout << i << '\n';
}


You'll see that this is how scanf() is used, for instance.

In C++ you can achieve the same thing using references, but in C you couldn't. It can be argued that passing a pointer is more clear.

[dennism12a]

In C brackets [] have a higher precedence than the asterisk *

[Sunny]

It's just an example.
Again, why would you need to get the address of a variable stored in memory?If you scratching your head, please re-read the title of this thread..

How Alvaro said: „to change the value of a variable with a function“

Maybe it isn't clear for you yet, but after a while you will understand the point of pointers!

try this:

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#include <iostream>

void addFive_byvalue(int x) { // here is 'x' just a copy of the 'x' that we pass. programmer would say: „call by value“
    x = 4;
}
void addFive_byreference(int* x) { // here is 'x' a ptr which will contain the address of our 'x' variable. programmer would say: „call by reference“
    x = 4;
}

int main() {
    int x = 0;
    addFive_byvalue(x);
    std::cout << "by value: " << x << std::endl; // 0
    addFive_byreference(&x); // here would the function change the variable 'x'
    std::cout << "by reference: " << x << std::endl; // 4
}

[JamsPeter]

Hi all. I have a VERY basic question regarding parenthesis.

1. What does the parenthesis mean after variables? For Example:

Code: Select all

int Main()

or

Code: Select all

void Something (void)

I don't understand when and why you need these. Also, for the above line of code, why do you need void inside the ().

Parenthesis defines that this is function or method. Only function consumes parenthesis.
Additional, Void in side the parenthesis describe function can accepts Parameter value. You can also write without void.

[evelyn512]

You posted a very helpful information. I could finally fix my challenge. Great work guys:)