C....

Question

Which of the following statements is correct:

a)Void pointers can be used for dereferencing.

b)Arithmetic operations can be applied on void pointers.

c)The default value of extern storage class is garbage value.

d)A particular extern variable can be declared many times, but canbe initialized at only 1 time.

 

[plz. give examples]

Comments

a)void pointers cant be used for derefrencing directly..only after typpecasting to pointed datatype.

b)arithmetic is not allowed on void pointers cuz it can point to anydatatype

c)i think the default value of extern storage class is 0 like global variables

d)yes,extern variables can be declared many times but can be defined only once..this is true with any variable

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@Akriti

Any example of a)?

and also see my command below

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int a=10;

void *p =&a;

printf("%d",*p)//not allowed

printf("%d",*(int *)p) //alowed

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When a variable is preceded wit extern keyword then it means memory is not allocated so you can declare it multiple number of times 

int var // memory 4b is allocated 

extern int var // memory not allocated

extern int var; int main(void) {  var = 10;  return 0; }

compilation error

http://www.geeksforgeeks.org/understanding-extern-keyword-in-c/