# What do memory configurations like “256Kx18” mean?

This is a beginner question here. When choosing memory ICs, one of the options is the memory size/configurations. I understand the size part, but what does the "16Kx9" mean? It seems the same memory size is usually available in different configurations. I attached a screenshot from Digikey as an example.

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What hasn't been mentioned in the answers yet: if the configuration is some multiple of 9, it generally means that you're dealing with some combination of 8 bit bytes and 1 bit parity. –  Robert Harvey Mar 7 '14 at 20:36
Usually, although there is no requirement to use it in that manner. –  Ignacio Vazquez-Abrams Mar 7 '14 at 23:02
that's good point. thanks guys for your great answers - good karma :) –  wildwildwilliam Mar 13 '14 at 19:26

When you say it will have a 14-bit address structure, is this a common property of all memory or is it derived from the aforementioned 16k x 9 notation? –  JYelton Mar 7 '14 at 21:29
@JYelton $2^{14}$ = 16,384 and 16k (binary speak) is 16,384 and uses 14 address lines. Not sure I've answered your question? –  Andy aka Mar 7 '14 at 21:38