self doubt

Question

please explain the memory allocation of statement , means how it works

register int a= 10;

Comments

means we are giving value of a=10 to registers   but it doesnt mean that register will store this value . we are just giving this value storing this depends on whether registers are free and many other points

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what all other points will be there? please explain in details.

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When will the memory allocation be - at compile time or at run time?

Answer 1

SO register a=10 means we are giving value of a=10 to registers   but it doesnt mean that register will store this value . we are just giving this value storing this depends on whether registers are free and many other factors 

OTHER FACTORS HERE ARE 

1) if we use & with register variable  means we are going to access address here . then some compiler show error or some warning.

as we dont access register address. It is invalid.

register int i = 10;

  int *a = &i; it is invalid

2)REGISTER is a storage class . in c we cant use multiple storage classs at a time.

means we cant use static register int a : it is invalid

 

3) we cant put *with register variable

 register int *a = &i; it is valid

we can use give ass no. of registers commands but only access to few

CREDIT ;  

Somoshree Datta 5  The register declaration can be applied only to automatic variables and formal parameters of a function.

 

 

Comments

Thanks for the explanation

Please tell me memory allocation time also

Whether at compile time or run time?

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from my prespective it is run time. as in compile time we will allocate things which are definitely assigned we dont know whether it is going to assign or not as sometimes if registers free at run time then assign it otherwise not. so .............. they are definitely run time

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@Deepanshu  a point which isnt mentioned in your answer

The register declaration can be applied only to automatic variables and formal parameters of a function.

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hmm also add that thanku Somoshree Datta 5