Automatic variables default intial value

[chibi.coder]

Why the default initial value of automatic variables are garbage values? Why not 0 like static and global variables initial value?

[CommonTater]

C has no "automatic" variables...

Global variables are declared at compile time and set to 0
Function-local variables are declared on the stack and are not initialized to any set value... so you get to do it yourself.

This should present no problem to a careful programmer.

[chibi.coder]

I actually meant auto type variables (variables store values automatically) .Thanks for explanation though.

[dmh2000]

K&R second edition page 31 : 'Each local variable ... such variables are usually known as automatic variables, following terminology in other languages'

[cas]

Why the default initial value of automatic variables are garbage values?

Probably because that could impose a penalty each time a function is entered. Zeroing values at startup is not difficult (even if it takes time it only happens once), but automatic variables are created each time a function starts, so you'd be creating overhead every time you zero them out. C generally takes the approach of making the implementor's life easy (and possible) rather than the programmer's life, so C can run everywhere.

It's also in part, I suspect, because that's just how it was done on Unix and the original C standard tended toward codifying existing behavior.

[iMalc]

Why the default initial value of automatic variables are garbage values? Why not 0 like static and global variables initial value?

Quite simply because C & C++ have the motto that you don't pay for what you don't use.

If you don't need an initial value of zero, then you don't pay the performance penalty of having the language do so unnecessarily.