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Applying the rules recursively to a source string of symbols will usually terminate in a final output string consisting only of terminal symbols. Consider a grammar defined by two rules. In this grammar, the symbol Б is a terminal symbol and Ψ is both a non-terminal symbol and the start symbol. The production rules for creating strings are as ...
Output is not sent to the terminal, but discarded, until another Control-o is typed. 7 Control-Q has been used to tell a host computer to resume sending output after it was stopped by Control-S. 8 Control-S has been used to tell a host computer to postpone sending output to the terminal. Output is suspended until restarted by the Control-Q key.
where A, B, and C are nonterminal symbols, the letter a is a terminal symbol (a symbol that represents a constant value), S is the start symbol, and ε denotes the empty string. Also, neither B nor C may be the start symbol, and the third production rule can only appear if ε is in L(G), the language produced by the context-free grammar G.
Database administration is the function of managing and maintaining database management systems (DBMS) software. Mainstream DBMS software such as Oracle , IBM Db2 and Microsoft SQL Server need ongoing management.
Some non-standard implementations of SELECT can have persistent effects, such as the SELECT INTO syntax provided in some databases. [ 2 ] Queries allow the user to describe desired data, leaving the database management system (DBMS) to carry out planning , optimizing , and performing the physical operations necessary to produce that result as ...
Have you ever wondered why an interviewer asks certain interview questions? Some of the questions seem so vague and random that it can be hard to figure out the logic behind the interview process.
On video terminals and other electronic output devices, there are often software (or hardware) configuration choices that allow a destructive backspace (e.g., a BS, SP, BS sequence), which erases, or a non-destructive one, which does not. The shift in and shift out characters (SI and SO) selected alternate character sets, fonts, underlining, or ...
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term " schema " refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases ).