3i Infotech Papers: Sample Questions 174  175 of 1245
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Question number: 174
Describe in Detail
What is an Oracle Instance?
Explanation

All running Oracle database is related with an Oracle instance.

Oracle allocates a memory area called the System Global when a database is started on a database server Area and starts one or more Oracle processes.

Oracle instance is the combination of the SGA and the Oracle processes.

An Oracle instance can access only one database at a time, while an Oracle database can be accessed by multiple instances.

Oracle databasewide system memory is known as the SGA, the system global area or shared global area.

The data and control structures in the SGA are shareable, and all the Oracle background processes and user processes can use them.
Question number: 175
Describe in Detail
What are the notations used in Evaluation of Arithmetic Expression using prefix and postfix forms?
Explanation

Polish and reverse polish are the notations used in evaluation of arithmetic expression using prefix and postfix forms.
Polish notation:

Polish notation is also called as prefix notation.

A form of notation for logic, arithmetic, and algebra.

Its distinguishing feature is that it places operators to the left of their operands.

While prefixing the operator to the number, it is called polish notation.
For example, ( (a + B) *C (D E) ^ (F + G) )
Prefix notation: ^*+ABCDE + FG
Reverse Polish notation:

A mathematical notation where every operator follows all of its operands, in contrast to Polish notation, which puts the operator in the prefix position.

It suffixes the operator to the number called reverse polish notation.
Ex. . ( (a + B) *C (D E) ^ (F + G) )
Postfix notation: AB + C*DE—FG+^