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COP 4020 Final Exam Questions and Answers
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COP 4020 Final Exam Questions and Answers
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COP 4020 Final Exam Questions andAnswers
Language design - Answer-computer languages allow humans to communicate
effectively in many domains,
Expressivity - Answer-why different languages are appropriate for different domains
Interpreters - Answer-directly executes instructions
(used for Perl, Python)
Compilers - Answer-converts programs to object code
(used for C, C++)
REPLs - Answer-Read, Evaluate, Print, Loops
(think Python environment)
lexical analysis - Answer-First phase of a compiler
Remove comments and identifying tokens in a sequence of characters
flex or re2c
Syntax analysis - Answer-Second phase of a compiler
Checks if the given input is in the correct syntax for the specific programming language
Semantic activities - Answer-Checks that the code has a meaningful sequence of
tokens
int a = "value";
lexically and syntactically correct, but it is an error because the type of assignment
differs.
Code generation - Answer-Last phase of a compiler,
Converts intermediate code to executable machine code.
Phases of compilation - Answer-1. Scanning (lexical analysis)
2. Parsing (syntax analysis)
3. Semantic analysis and intermediate code generation
4. Maybe some optimization
5. Target code generation
, 6. Code improvement on the final code (peephole
optimization)
Regex mechanisms - Answer-Concatenation (xy)
Alternation (x | y)
Repetition (aka Kleene closure)
Context-free grammar additional mechanism - Answer-Recursion
a(?R)?z to match "aaazzz"
Parser - Answer-a language recognizer.
Two types, LL and LR
LL parsers - Answer-top-down parsers (usually written by hand)
"Left-to-right, Left-most derivation"
recursive-descent parsing
LR parsers - Answer-bottom-up parsers (usually created with a parser generator)
"Left-to-right, Right-most derivation"
recursive-descent parsing - Answer-For each non-terminal, we write one function of the
same name
Each non-terminal is turned into a function call of that non-terminal's function, and each
terminal is made into a call for a match
If a production has alternatives, these alternatives must be distinguished by using the
predict set.
Recursive Descent - Answer-Each non-terminal becomes a function with the same
name
Each terminal is made into a call for a match
top-down parsing - Answer-a predictive form of parsing, such as recursive descent, in
which the parse tree of a statement is constructed starting at the root
bottom-up parsing - Answer-input words are matched against the right-hand sides of
grammar productions in an attempt to build the parse tree from leaves to root
parsing stacks - Answer-a top-down parser's stack contains a list of what the expects to
see in the future
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