CS326
CS 326 Final Exam 2025
Generate a Grammar that is Syntactically Valid, but show an input string that would not
type check.
(test question from subprograms slide part 2) - Correct Ans-e = expression
f = factor
start -> e ';'
e -> e +/- f | f
f -> f */ / atom
| atom
atom -> string
| int
"Bob" / 26 ; //could be valid string if you want it to be
it is syntactically valid but semantically drugs.
What is "auto-boxing" - Correct Ans-Conversion between primitive types and the
corresponding wrapper classes is automatic.
ie. int a = 10;
Integer b = a; //Auto boxing (int to Integer)
int c = b; // Unboxing (Integer to int)
ie.
Primitive Data Types:
These are the basic data types in Java such as 'int' , 'double', 'char', and 'boolean'. They
are not objects and do not belong to any class. They are stored efficiently and have a
lower memory footprint.
Wrapper Classes: for every primitive data type in Java, there is a corresponding
wrapper class, like 'Integer' for 'int', 'Double' for 'double', 'Character' for 'char', and
'Boolean' for 'boolean'. These classes encapsulate the primitive data type in an object
allowing them to be used in places where only objects can be utilized.
Auto Boxing - is the process where the Java compiler automatically converts the
primitive type into its corresponding wrapper class object. For example, when you type
int, to an Integer object, Java automatically converts the int to an Integer.
Unboxing the reverse process called unboxing, where the object of a wrapper class is
converted back to a primitive type
What is the potential negative about "auto boxing" in relation to Java?
CS326
,CS326
Think int -> Integer
(Lec 10.19.23) Subprograms 3 - Correct Ans-Has to be an object because Java weaves
it into the bytecode that way. Under the hood, when calling a generic, the generic is
called an object type. Thus, it has to be that way or the program does not work -
mathematically required. The problem is objects are generally bigger and slower.
Instead of using ALU - you have to make an object to put in a variable which all takes
time.. size of object + heap + field of actual 32 bits and something to access
(getter/setter/caller) which all takes up some space.
Generic is called
The syntax of a programming language is?'
ref ch 3 - Correct Ans-The form of its expressions, statements, and program units.
The semantics of a programming language is?
ref ch 3 - Correct Ans-The meaning of those expressions, statements, and programming
units.
Why are syntax and semantics closely related?
ref ch 3 - Correct Ans-A well-designed programming language, semantics should follow
directly from syntax; that is, the appearance of a statement should strongly suggest
what the statement is meant to accomplish.
Strings of a language are called? - Correct Ans-sentences or statements.
What are Lexemes?
ref ch 3 - Correct Ans-lowest-level of syntactical units. They include its numeric literals,
operators, and special words, etc.
One can think of programs as strings of lexemes rather than characters
What are Identifiers?
ref Ch 3 - Correct Ans-Identifiers - when partitioned into groups (ie. names of variables,
classes, etc)
What are Tokens?
CS326
, CS326
ref ch 3 - Correct Ans-Each lexeme group that is represented by a name or token. So, a
token of a language is a category of its lexemes.
What is a grammar?
ref ch 3 - Correct Ans-Grammars are formal language-generation mechanisms. They
commonly are used to describe the syntax of a programming language
Who created Context-Free Grammars?
ref ch 3 - Correct Ans-Noam Chomsky
Who created BNF?
ref ch 3 - Correct Ans-John Backus and Peter Naur
What is BNF?
ref ch 3 - Correct Ans-It is a natural notation for describing syntax.
What is a meta-language?
ref ch 3 - Correct Ans-A metalanguage is a language that is used to describe another
language. BNF is a metalanguage for programming languages.
<assign> -> <var> = <expression>
Define the LHS and RHS
ref ch3 - Correct Ans-LHS of arrow (->) is the abstraction being defined
RHS of arrow (->) is the definition of the LHS.
RHS consists of some mixture of tokens, lexemes, and references to other abstractions.
(Tokens are also abstractions)
In reference to the RHS, what is the definition called?
ref ch 3 - Correct Ans-definition is called a rule or production.
ie. a rule is just given, the abstraction <var> and <expression> obviously must be
defined for the <assign> definition to be useful.
This particular rule specified that the abstraction <assign> is defined as an instance of
the abstraction <var>, followed by the lexeme " = ", followed by an instance of the
abstraction <expression>
CS326
CS 326 Final Exam 2025
Generate a Grammar that is Syntactically Valid, but show an input string that would not
type check.
(test question from subprograms slide part 2) - Correct Ans-e = expression
f = factor
start -> e ';'
e -> e +/- f | f
f -> f */ / atom
| atom
atom -> string
| int
"Bob" / 26 ; //could be valid string if you want it to be
it is syntactically valid but semantically drugs.
What is "auto-boxing" - Correct Ans-Conversion between primitive types and the
corresponding wrapper classes is automatic.
ie. int a = 10;
Integer b = a; //Auto boxing (int to Integer)
int c = b; // Unboxing (Integer to int)
ie.
Primitive Data Types:
These are the basic data types in Java such as 'int' , 'double', 'char', and 'boolean'. They
are not objects and do not belong to any class. They are stored efficiently and have a
lower memory footprint.
Wrapper Classes: for every primitive data type in Java, there is a corresponding
wrapper class, like 'Integer' for 'int', 'Double' for 'double', 'Character' for 'char', and
'Boolean' for 'boolean'. These classes encapsulate the primitive data type in an object
allowing them to be used in places where only objects can be utilized.
Auto Boxing - is the process where the Java compiler automatically converts the
primitive type into its corresponding wrapper class object. For example, when you type
int, to an Integer object, Java automatically converts the int to an Integer.
Unboxing the reverse process called unboxing, where the object of a wrapper class is
converted back to a primitive type
What is the potential negative about "auto boxing" in relation to Java?
CS326
,CS326
Think int -> Integer
(Lec 10.19.23) Subprograms 3 - Correct Ans-Has to be an object because Java weaves
it into the bytecode that way. Under the hood, when calling a generic, the generic is
called an object type. Thus, it has to be that way or the program does not work -
mathematically required. The problem is objects are generally bigger and slower.
Instead of using ALU - you have to make an object to put in a variable which all takes
time.. size of object + heap + field of actual 32 bits and something to access
(getter/setter/caller) which all takes up some space.
Generic is called
The syntax of a programming language is?'
ref ch 3 - Correct Ans-The form of its expressions, statements, and program units.
The semantics of a programming language is?
ref ch 3 - Correct Ans-The meaning of those expressions, statements, and programming
units.
Why are syntax and semantics closely related?
ref ch 3 - Correct Ans-A well-designed programming language, semantics should follow
directly from syntax; that is, the appearance of a statement should strongly suggest
what the statement is meant to accomplish.
Strings of a language are called? - Correct Ans-sentences or statements.
What are Lexemes?
ref ch 3 - Correct Ans-lowest-level of syntactical units. They include its numeric literals,
operators, and special words, etc.
One can think of programs as strings of lexemes rather than characters
What are Identifiers?
ref Ch 3 - Correct Ans-Identifiers - when partitioned into groups (ie. names of variables,
classes, etc)
What are Tokens?
CS326
, CS326
ref ch 3 - Correct Ans-Each lexeme group that is represented by a name or token. So, a
token of a language is a category of its lexemes.
What is a grammar?
ref ch 3 - Correct Ans-Grammars are formal language-generation mechanisms. They
commonly are used to describe the syntax of a programming language
Who created Context-Free Grammars?
ref ch 3 - Correct Ans-Noam Chomsky
Who created BNF?
ref ch 3 - Correct Ans-John Backus and Peter Naur
What is BNF?
ref ch 3 - Correct Ans-It is a natural notation for describing syntax.
What is a meta-language?
ref ch 3 - Correct Ans-A metalanguage is a language that is used to describe another
language. BNF is a metalanguage for programming languages.
<assign> -> <var> = <expression>
Define the LHS and RHS
ref ch3 - Correct Ans-LHS of arrow (->) is the abstraction being defined
RHS of arrow (->) is the definition of the LHS.
RHS consists of some mixture of tokens, lexemes, and references to other abstractions.
(Tokens are also abstractions)
In reference to the RHS, what is the definition called?
ref ch 3 - Correct Ans-definition is called a rule or production.
ie. a rule is just given, the abstraction <var> and <expression> obviously must be
defined for the <assign> definition to be useful.
This particular rule specified that the abstraction <assign> is defined as an instance of
the abstraction <var>, followed by the lexeme " = ", followed by an instance of the
abstraction <expression>
CS326
