SystemVerilog Data Types — 2-State, 4-State & Nets

The type you declare decides three things at once: what values the object can hold, whether the tool will let you drive it from more than one place, and whether an uninitialised read is visible. Choosing `int` over `integer` in a counter is not style — a 4-state counter starts at X and stays X, and `%0d` prints that as zero, so the bug looks like a counter that never counted. Most type decisions in this cluster are of that shape: the wrong choice is legal, compiles clean, and hides its own symptom.