524 questions and answers
What do you mean by a Handle? Give example. When a grammar is called ambiguous? Is there any technique to remove ambiguity? Explain with an example. What is the reduce-reduce conflict in LR parser? What are various data structures used for symbol table construction?
A handle of a string is a substring that matches the right side of a production, and whose reduction to the non-terminal on the left side of the production represents one step along the reverse of a rightmost derivation.
Describe various actions of a shift reduce parsers.
Actions of shift-reduce parsers: A shift-reduce parser works by doing some combination of Shift steps and Reduce steps, hence the name.
With suitable examples, show how recovery in a database system can be done using Log Files with
Deferred Update Recovery Also called NO-UNDO/REDO
Consider the relation R={A,B,C,D,E,F,G,H,I,J} and the set of functional dependencies: F={AB → C, A → DE, B → F, F → GH, D → IJ}. Decompose R into 3NF.
A→DE, so AB→BDE (Augmentation) AB→C, so AB→ABC (Reflexivity)
What is the difference between a database and a table? Why are entity integrity and referential integrity important in a database?
Difference between database and a table: A table is an object inside a database. A database has tables of data, views, indexes and programs. A database can have 10 or thousands of tables.
Explain two-phase locking protocol.
In a multiprogramming environment where multiple transactions can be executed simultaneously,
Write short notes on the following:
Armstrong’s Axioms: An inference axiom is a rule that states if a relation satisfies certain Functional Dependencies (FDs) then it must satisfy certain other FDs.
Write short notes on the following:
View Serializability Let S and S0 be two schedules with the same set of transactions. S and S0 are view equivalent if the following three conditions are met:
Describe the wait-die and wound-wait protocols for deadlock prevention. Define three concurrency problems: dirty read, non-repeatable read, phantoms.
We can prevent deadlocks by giving each transaction a priority and ensuring that lower priority transactions are not allowed to wait for higher priority transactions (or vice versa).
What do you mean by input buffering? How is input buffering implemented? What problem can arise implementing input buffering? Give suitable example. What is sentinel? What is its use?
The Lexical Analyzer scans the characters of the source program one at a time to discover tokens.
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