Computer Science and IT
Computer science and IT questions cover programming, data structures, algorithms, databases, operating systems and basic networking. The exam tends to test complexity, correct output and standard definitions; precise reasoning is more valuable than memorised code.
Core rules and concepts
- Complexity: binary search O(log n) on sorted data; linear search O(n); good sorting O(n log n); nested loops often O(n²).
- Structures: arrays give O(1) indexed access; linked lists give O(1) insertion at a known node; stacks are LIFO; queues FIFO; balanced trees O(log n).
- DBMS: keys enforce identity; ACID = atomicity, consistency, isolation, durability; 1NF atomic values, 2NF removes partial dependency, 3NF removes transitive dependency.
- SQL: DDL creates/alters schema; DML changes rows; SELECT is retrieval; joins combine relations by a predicate.
- OS: a thread shares its process address space; a process has separate memory. Deadlock needs mutual exclusion, hold-and-wait, no preemption and circular wait.
- Networks: TCP uses a handshake and retransmission; UDP is datagram-oriented; DNS resolves names; IP delivers packets.
- C: parameters pass by value; arrays decay to pointers; pointer arithmetic scales by the pointed-to type.
Worked example
Binary search on 1024 sorted records: after one comparison the interval is at most 512, then 256, 128, 64, 32, 16, 8, 4, 2, 1. That is log2(1024) = 10 comparisons in the worst case, not 1024. Linear search would need up to 1024 comparisons, so the sorted-order precondition is the key.
Traps that cost marks
Run binary search on unsorted data; quote O(log n) for search while ignoring the O(n log n) sort cost; confuse 1NF with 3NF; assume a thread has its own address space; expect UDP handshakes; forget zero-based array indexing.