focus on core concepts such as data structures (arrays, linked lists, stacks, queues, trees, graphs, hash tables), and fundamental algorithms like sorting, searching, and dynamic programming, with a clear understanding of time and space complexity. Brush up on operating system concepts like processes, threads, memory management, and deadlocks. Master networking basics such as TCP/IP, HTTP, and DNS, along with database topics like SQL, joins, and normalization. Be well-versed in object-oriented programming (OOP) principles such as encapsulation, inheritance, and polymorphism.