What are the values?

Question

I'm trying to learn C and have been trying a few exercises in a book I have found on the internet.

This question will probably be easy for you experts, What are the values displayed in the watch window when I watch some of the variables. I am referring to its state BEFORE a value is assigned to the variable. They are usually long numbers with about 10 digits and sometimes negative.

I know this may seem a silly question, but I am curious as to what they are. At first I thought they were addresses.

Most likely you are seeing whatever was in memory before the variable was initialized. — NathanOliver, Jul 15 '16 at 16:42
Values of default-intialized variables having scalar types are indeterminate. — MikeCAT, Jul 15 '16 at 16:43
this is related http://stackoverflow.com/questions/1597405/what-happens-to-a-declared-uninitialized-variable-in-c-does-it-have-a-value — nicks, Jul 15 '16 at 16:44

score 2 · Answer 1 · answered Jul 15 '16 at 16:44

Since memory is not reset to a particular value when it is deallocated or reallocated, you will see whichever value was left there by the last code that was using that memory.

This can sometimes be a security issue. For example, if if that memory contained a password or other sensitive information. Hence for certain applications, it is important to zero-out the memory before freeing it.

score 2 · Answer 2 · answered Jul 15 '16 at 16:45

Before you assign a value to a variable, it has whatever happened to be in that memory previously. It's very likely that the memory for a variable in one function was used for a variable of a different type in some other function. If the previous use was for a float or pointer, and now you're using it for an int, the value will look very random.

What are the values?

2 Answers2