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call by value call by reference difference

masiht (222)
Can anyone please explain the difference between call by value and call by reference in simple words , I read the explaination here but didn't get it.
please tell me in simple words.
helios (17574)
When passing data by value, the data is copied to a local variable/object in the function. Changes to this data are not reflected in the data of the calling function. For larger objects, passing data by value can be very expensive.
When passing data by reference, a pointer to the data is copied instead. Changes to the data pointed to by the pointer are reflected in the data of the calling function. Regardless of the size of the object, passing data by reference always has the same cost.

Example:
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void by_value(int a){
	a+=10;
}

void by_ref(int *a){
	(*a)+=10;
}

void by_ref2(int &a){
	a+=10;
}

int main(){
	int x=40;
	by_value(x);
	//x==40
	by_ref(&x);
	//x==50
	by_ref2(x);
	//x==60
	return 0;
}

by_ref() demonstrates the syntax used to pass data by reference using pointers. by_ref2() demonstrates the syntax used to pass data by reference using references.
Do not confuse passing by reference with passing with references. It's possible to pass by reference without passing with references, but passing with references always passes by reference.
Last edited on
masiht (222)
Can I say that whenever the function has & sign it is call by reference and whenever a function doesn't have any & sign , the function is call by value always and for sure.
Last edited on
jsmith (5804)
Parameters are passed by value, reference, or pointer. A reference parameter looks like line 9 above.

You can have a function that takes multiple parameters - some by reference, some by value, some by pointer.

masiht (222)
Can I say if the parameters within the function has * or & in it ,it is call by reference otherwise call by value ?
masiht (222)
Please !! Answer in yes or no .

Can I say if the parameters within the function has * or & in it ,it is call by reference otherwise call by value ?
Last edited on
helios (17574)
Yes.
masiht (222)
does it mean that if the function has pointer in it , it is always call by reference ?
helios (17574)
Could you give an example?
masiht (222)
like when the function is call by reference if the parameters have * and & signs similarly, pointers have * and & signs ,
so what is the relation between pointers and call by reference ?
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