For "A is a drop-in replacement for a B" what is 'drop-in'?
How are you guys?

I have a question of 'drop-in'.

I found this sentences from a book.

The sentence is "A is a drop-in replacement for a B, the only difference is that As are ....".

From those sentences, I infered that 'drop-in' might be meant small or just some part of.

Am I right? Or it means just drop by?

Thanks for your time.

Question

For "A is a drop-in replacement for a B" what is 'drop-in'?
How are you guys?

I have a question of 'drop-in'.

I found this sentences from a book.

The sentence is "A is a drop-in replacement for a B, the only difference is that As are ....".

From those sentences, I infered that 'drop-in' might be meant small or just some part of.

Am I right? Or it means just drop by?

Thanks for your time.

Answer

Maybe this discussion will help:

https://ell.stackexchange.com/questions/19853/what-does-a-drop-in-replacement-mean/38823

Answer

A 'drop-in replacement' is any part that is a direct replacement for the original part. It means something that does the same, or a better job as the original part, without any modifications to the larger thing.
It can certainly be used in a software sense, but that is only a subsection of the possible areas you could use it.
"You can buy circuit breakers that are drop-in replacements for your old ceramic fuses".
"You could get one of those drop-in replacement ignition systems to replace those old unreliable points on your old car".
"Replace that lamp with one of those drop-in replacement LED lamps. Then you won't have to keep replacing it".