Howto interpret smartctl return values

When using smartctl the return value can provide some useful information but it requires looking up what the individual set bits mean. After running smartctl on a large number of drives here are the codes I found and looked up:

• 32 = SMART status check returned “DISK OK” but we found that some (usage or pre-fail) Attributes have been <= threshold at some time in the past
• 64 = The device error log contains records of errors
• 96 = Both of the above