Justification

Without declaration there is no prototype checking and that is error-prone.

Example

static int ccbb_f(); /* WRONG: old style declaration */
static int ccbb_f(float); /* WRONG: incomplete declaration */

static int ccbb_f(float angle); /* RIGHT: type & name of parameter mentioned */

static int ccbb_f(angle) /* WRONG: old style definition */
float  angle;
{
}

static int ccbb_f(float angle) /* RIGHT: ANSI style definition */
{
}