What does the "In-line" in SIMM and DIMM memory mean?

Question

I've been searching for what exactly the "in-line" part means but I don't get it. Is it the way the chips are positioned, as in a line? If it is, is there another possible configuration?

Answer 1

The "in-line" is about all the contacts being in a straight line on the edge of the PCB.

The SIMM has only actually one set of contacts: the contacts on either side of the PCB are connected.

You can see that on a photo of the slot; there is only one contact for both sides.

^{source: wikimedia user Wolfgang "Darkoneko" ten Weges}

On a DIMM, both sides of the PCB carry one line of different contacts:

^{source: wikimedia user Project Keil}