What is Program to Interface?
Write code against a contract, not a specific implementation. Swap implementations without rewriting callers.
same socket · real or fake store
Program to Interface means callers use…
Write it in your own words in the app.
In real work
Program to interface: checkout depends on StorageProtocol, not S3Client, so local dev can use a fake store.
In the illustration
The S3 store unit unplugs and a small fake store with the identical plug slots into the same socket; the checkout machine's lamp never flickers.
Have your coding agent program to interface for the payment layer: define a PaymentProvider protocol, make Stripe and the test double conform, and swap them by injection rather than by import.
Try it now
The fastest way to learn a word is to use it. Open this line in the agent you already work in and watch what it does. Change the tool to the one you use.
Go further
01Practice
Make it stick
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02Verify
Prove you know it
Pass the quiz and keep it in a Skills Wallet you can share with anyone who needs proof.
03Career
Find the work that uses it
See which roles lean on this vocabulary, and what they pay in year one.
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