Customer service system (C)

A customer service system built in plain C: registering and updating customers, and a request-accept-reject workflow for the services they asked for, using structs, pointers, linked lists, queues, and stacks, and manual memory management throughout, no garbage collector doing the work quietly in the background.

Every allocation had to be tracked and freed explicitly, and getting the data-structure choices right, a linked list for one part of the model, a queue for pending requests, mattered more here than in almost any other module in the degree, since a wrong choice showed up immediately as a memory leak or a crash rather than a slow abstraction.

It's the lowest-level project in the whole degree, and deliberately placed early: understanding what a linked list or a queue actually costs in raw memory before ever getting to use a language that hides that cost.