question about variable initializations

jackhasf · 11-07-2009, 10:48 AM

let's say we have this code

Code:

main()
{
int k;
while (k!=0)
{
scanf("%d",&k);
printf("%f\n",100/k);
}
}

our teacher said that this will stop because k would have value of 0

but, this is not true cause when i run it, it works for me.

so i would like to ask, what are the variable initializations in C? If we give a variable no value, will it have value of 0?

thanks

Dino · 11-07-2009, 10:52 AM

A global variable will be initialized to zero if you don't explicitly initialize it with something else.

A local variable, such as you have, will be indeterminate.

MK27 · 11-07-2009, 10:55 AM

Quote:

Originally Posted by jackhasf

so i would like to ask, what are the variable initializations in C? If we give a variable no value, will it have value of 0?

I believe the C standard does guarantee uninitialized GLOBAL variables are set to 0/NULL -- but I'm not positive, since I always set it myself if that's what I want.

Otherwise (eg, in the case of a stack variable local to main(), as you have above) the memory address is not cleared and could contain any value.

King Mir · 11-07-2009, 11:19 AM

Technically, Only integer values are guaranteed to be 0 in the global scope. Other types will be equal to whatever all zeros represents for that type. This means that technically pointers and floating point numbers are not guaranteed to be set to NULL/0.0, as the C standard does not specify how these are encoded. They are not garunteed unless you assume IEEE floating point, and that a NULL points to the 0th address. Both of these are solid assumptions for any system.

11-07-2009, 10:48 AM	#1
jackhasf Registered User Join Date: Feb 2009 Posts: 10	question about variable initializations let's say we have this code Code: main() { int k; while (k!=0) { scanf("%d",&k); printf("%f\n",100/k); } } our teacher said that this will stop because k would have value of 0 but, this is not true cause when i run it, it works for me. so i would like to ask, what are the variable initializations in C? If we give a variable no value, will it have value of 0? thanks
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11-07-2009, 10:52 AM	#2
Dino Jack of many languages Join Date: Nov 2007 Location: Katy, Texas Posts: 1,929	A global variable will be initialized to zero if you don't explicitly initialize it with something else. A local variable, such as you have, will be indeterminate. __________________ Mac and Windows cross platform programmer. Ruby lover. Memorable Quotes From Recent Posts: I can't remember.
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11-07-2009, 11:19 AM	#4
King Mir Registered User Join Date: Apr 2006 Posts: 1,193	Technically, Only integer values are guaranteed to be 0 in the global scope. Other types will be equal to whatever all zeros represents for that type. This means that technically pointers and floating point numbers are not guaranteed to be set to NULL/0.0, as the C standard does not specify how these are encoded. They are not garunteed unless you assume IEEE floating point, and that a NULL points to the 0th address. Both of these are solid assumptions for any system. __________________ It is too clear and so it is hard to see. A dunce once searched for fire with a lighted lantern. Had he known what fire was, He could have cooked his rice much sooner.
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