CS 375, Compilers: Study Guide for Midterm Exam

Date: Tuesday, October 21, 2025, at class time, on Canvas.

Reading:

Class lecture notes through page 157. Optionally, Aho, Lam, Sethi, and Ullman, Compilers: Principles, Techniques, and Tools, Chapters 1; 3 through 3.5; 4 through p. 220, 4.5, 4.6.3, 4.9; 5.1, 5.3; 6 through 6.5, 2.7.

Material covered in class:

Major phases of a compiler; what the phases do; data flow between phases.
Formal definition of a grammar; chart about grammar classes.
Regular languages: grammar definitions, uses; local ambiguity: examples, ways to handle. Relationship of finite automata and regular grammars; linear nature of a derivation from a regular grammar.
Regular expressions: definition; be able to construct a regular expression for a language, or to describe the language denoted by a regular expression. Regular expressions and finite automata can also describe regular languages. lex constructs a table-driven finite automaton from regular expressions.
Lexical analyzer: what constructs are parsed; lex.
Context-free languages: grammar definition; stack needed for parsing. Notations for defining the syntax of a language: BNF, Yacc, Pascal-style transition diagrams. Ambiguous grammars vs. unambiguous grammars. Augmented transition network; Yacc. Context-free language features include recursion, balanced parentheses, counting.
Derivation from a context-free grammar: relationship to parse tree, notations for a derivation, definition of a language in terms of derivations.
Operator precedence grammar and parser: definitions; precedence numbers, associativity. How operator precedence parser works (be able to work an example).
Top-down parsing: definition; why backup may be required; for what kinds of languages does it work well; recursive descent parser; problems with left recursion; left factoring; implementation of top-down parser by a recursive program: be able to write a procedure for a construct such as an IF statement.
Shift-reduce parser: use of stack; four actions of shift-reduce parser.
Symbol tables: methods of organization; speed, advantages, disadvantages of each; comparisons; be able to select a method for a particular application. Search is more frequent than insertion. Symbol tables for lexical scoping in block-structured languages. What things are put in symbol tables? Kinds of symbols in a compiler. Methods of storing identifier names.
Data area and base-offset addressing; storage allocation algorithm; allocation of data in records; word alignment and padding; variant records.
Address calculations for array references (know the formulas). Address calculations for access to fields of a record; determining types of accesses to parts of a structure. Be able to calculate the size of an array of records; be able to calculate the address offsets for access to an array element and record field.

Vocabulary

abstract syntax tree (AST)	accepting state	address alignment
alphabet	ambiguity	ambiguous grammar
arity	associativity	augmented transition network (ATN)
AVL tree	base address	basic type
BNF	bottom-up parsing	cascading errors
cast	character class	Chomsky hierarchy
CKY chart parser	code generation	collision
compile-time	concatenation	context-free grammar
controllability	data area	declaration
derivation	deterministic finite automaton	disambiguating rules
dynamic	enumerated type	equivalent grammars
error production	finite automaton	fix
fixed-point	float	floating-point
grammar	hash function	hash table
hash with buckets	infix	insertion
intermediate language	Kleene closure	language denoted by a grammar
left-associative	left recursion	left factoring
leftmost derivation	lexeme	lexer
lexical analysis	mnemonic	NaN
nondeterministic finite automaton	nonterminal	object language
observability	offset	operand
operator	optimization	padding
parse tree	parsing	pass
postfix	precedence	prefix
preorder	production	recognizer
record	recursive descent	reduce
reduce-reduce conflict	reduction step	regular expression
regular grammar	regular language	rehash
reserved word	right-associative	scalar type
scope	semantics	shift
shift-reduce parser	shift-reduce conflict	significand
SNaN	sound	sound type system
start symbol S	static	storage allocation
string	subrange	substring
suffix	symbol table	syntax
syntax-directed translation	synthesized translation	table lookup
terminal	token	top-down parsing
top-down filtering	type	type constructor
type lattice	unary	variable
variable declaration	variant record	white space
yacc