Unit 4 - Chapter 11

Question 1

The program that performs lexical analysis is called a

Answer 1

lexical analyzer or more commonly, a scanner

Question 2

tokens

Answer 2

are syntactical units that are treated as single, indivisible entities for the purposes of translations.

Question 3

every scanner performs virtually the same set of operations:

Answer 3

(1) it discards blanks and other nonessential characters and looks for the beginning of a token; (2) when it finds the beginning, it puts characters together until (3) it detects the end of the token, at which point it classifies the token and begins looking for the next one. This algorithm works properly regardless of what tokens look like.

Question 4

parsing phase

Answer 4

a compiler determines whether the tokens are syntactically legal statement of the programming language.

Question 5

parse tree

Answer 5

It starts from the individual tokens in the statement, a,=,b,+,and c, and show how these tokens can be grouped into predefined grammatical categories such as , , and until the desired goal is reaches - in this case, . The successful constructions of a parse tree is proof that this statement is correctly formed according to the rules of the language. If a parser cannot produce such a parse tree, then the statement is not correctly formed.

Question 6

In the field of compiler design, the process of diagramming a high-level language statement is called

Answer 6

parsing. and it is done by a program called a parser.

Question 7

The parser must be given a formal description of the syntax - the grammatical structure - of the language that it is going to analyze. The most widely used notations for representing the syntax of a programming language is called

Answer 7

BNF, and acronym for Backus-Naur Form

Question 8

In BNF

Answer 8

the syntax of a language is specified as a set of rules, also called productions. The entire collections of rules is called a grammar.

Question 9

Terminals

Answer 9

are the actual tokens of the language recognized and returned by a scanner

Question 10

nonterminal

Answer 10

A nonterminal is not an actual element of the language but an intermediate grammatical category used to help explain and organize the language.

Question 11

Goal symbol

Answer 11

This is the final nonterminal, and it is the nonterminal object that the parser is trying to produce as it builds the parse tree.

Question 12

lambda λ represents

Answer 12

the null string - nothing at all. It is possible that a nonterminal can be “empty”, and the symbol λ is used to indicate this.

Question 13

look-ahead parsing algorithms

Answer 13

These algorithms “ look down the road” a few tokens to see what would happen if a certain choice is made.

Question 14

Recursive definition

Answer 14

defines the nonterminal symbol in terms of itself.

Question 15

Grammar that allows the construction of two or more distinct parse trees for the same statement is said to be

Answer 15

ambiguous.

Question 16

A semantic record is

Answer 16

a data structure that stores information about a nonterminal, such as the actual name of the object and its data type.

Question 17

Code generation

Answer 17

The compiler must determine how that transformation can be accomplished in machine language.

Question 18

Optimization

Answer 18

where the compiler polishes and fine-tunes the translation so that it runs a little faster or occupies a little less memory.

Question 19

Visual development environments

Answer 19

use graphics and video to let the programmer see what is happening

Question 20

Online debuggers

Answer 20

help programmers locate and correct errors.

Question 21

Reusable code libraries

Answer 21

contain a large collection of prewritten program units.

Question 22

When a compiler is embedded within a collection of supporting software development routines such as debuggers, editors, toolkits, and libraries, it is called

Answer 22

an integrated development environment (IDE).

Question 23

Local optimization

Answer 23

the compiler looks at a very small block of instructions, typically from one to five. It tries to determine how it can improve the efficiency of this local code block without regard for what instructions come before or after.

Question 24

Global optimization

Answer 24

the compiler looks at large segments of the program, not just small pieces, to determine how to improve performance.