[1] Pin compatibility is a property desired by systems integrators as it allows a product to be updated without redesigning printed circuit boards, which can reduce costs and decrease time to market.
Although devices which are pin-compatible share a common footprint, they are not necessarily electrically or thermally compatible.
The 7400 series devices have been produced on a number of different manufacturing processes, but have retained the same pinouts throughout.
In other cases, particularly with computers, devices may be pin-to-pin compatible but made otherwise incompatible as a result of market segmentation.
Examples of these include, CMSIS for ARM Cortex-M processors and the now-deprecated HAL subsystem for UNIX-like operating systems.