For all logic families, a totem pole output can source current when it is pulling a load high, or sink current when it is pulling a load low. An open collector output can sink only; it does not have the upper transistor in the output stage to pull a load high. Some logic devices have tri-state outputs, where both the pull up and pull down transistors are disabled; the output is in a high impedance state and does not sink or source current.
CMOS input stages have such a high input impedance that for all practical purposes they do not source or sink anything. Bipolar logic devices (original TTL, LS, F, etc.) have a common base amplifier for the input stage so whatever is driving them must be able to *sink* current out of the TTL input stage to pull it low. This is why unused input pins of these older logic types float high, whereas unused CMOS inputs float to an unknown state.
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