Scope and lifetime of a variable

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Scope vs life of variable in C

What exactly is the difference between the scope and lifetime of a variable in c? What is the scope and lifetime of a variable declared within a block inside a function?

-1: Did you try [Googling it](http://goo.gl/pYdpH)? – Eitan T Jul 12 '12 at 08:41 — Eitan T, Jul 12 '12 at 08:41

score 9 · Answer 1 · answered Jul 12 '12 at 08:42

Lets say we have two functions:

void foo()
{
    /* Do some stuff */
}

void bar()
{
    int local_bar;

    foo();

    /* Do some more stuff */
}

In the function bar the scope of the variable local_bar is all inside the function bar. When calling foo the variable temporarily goes out of scope, i.e. it's not available from inside of foo. However, the lifetime of the variable has not ended, it will only end when the function bar ends.

score 1 · Answer 2 · answered Jul 12 '12 at 08:38

1

It depends. Scope represents the blocks of code from which the variable can be accessed, lifetime represents the period from creation to destruction.

What is the scope and lifetime of a variable declared within a block inside a function?

In this case, they coincide:

{
   int x; // begin scope and lifetime
}  // end scope and lifetime

The difference arises in other cases, for example with globals. You declare an extern int x and define it somewhere. Its lifetime extends from the start to the end of the program, but it's scope is only in the files where you actually include the declaration.

answered Jul 12 '12 at 08:38

Luchian Grigore

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Also mention that `static` can have limited scope, but lifetime like a global. – jxh Jul 12 '12 at 08:54
Ya.in the above example,does it mean,a continues to have a lifetime outside } but has no scope? – Sneha S P Jul 12 '12 at 09:39
@SnehaSP no, for `{int x;}` both the scope and lifetime end with the closing `}`. – Luchian Grigore Jul 12 '12 at 09:41
Let me make this clear.if this block was inside a function ?would it still be the same? – Sneha S P Jul 12 '12 at 09:47

Scope and lifetime of a variable

2 Answers2