Are explicit declarations necessary?

[Hans Albertsson]

[]
Having looked through K&R carefully, and at lots of
C source too boot, I'm a bit bewildered; is code like

a;
funcname()
{
	a = 1;
	printf("%d",a);
}

at all permissible? Isn't it nessecary to declare a as int, even 
if my pcc-based compiler seems to think int is a kind of default?

As an aside, one of the contributions to the obfuscated code contest
did things like this.

K&R seems to permit dropping int only in connection with so called
"adjectives", that is:
unsigned a;
is ok, but only because unsigned is there.
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