What is a function — CCA-F Exam Prep

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REAL STORY Split screen. Left: a toaster with bread going in and toast coming out. Right: a chef in a kitchen surrounded by dozens of tools, ingredients, and half-finished dishes. Clean illustration.

Split screen. Left: a toaster with bread going in and toast coming out. Right: a chef in a kitchen surrounded by dozens of tools, ingredients, and half-finished dishes. Clean illustration.

A developer at a fintech startup wrote the credit card validation logic 47 times. In 47 different places across the codebase.

Then they discovered a bug in the validation. It was accepting expired cards. Fixing it meant finding and updating all 47 copies. They found 43. The other 4 stayed broken for six months -- silently accepting expired cards and processing $220,000 in charges that should have been rejected.