Exam 1 Topics
CS141: Introduction to Programming, Fall 2013

General Comments and Recommendations

• The exam will cover Chapters 1-4 of the text (up to and including loops).
• The exam will be 1 hour long. It will be closed book. Electronic devices, of any kind, will not be allowed.
• It is strongly recommended that students:
  • Re-read the text
  • Do the self-check exercises in each chapter (answers are in the text)
  • Review the reading quizzes
  • Review the programming code-completion and programming exercises.
• Practice Problems which could appear on the exam:
  • Variables (pdf)
  • Basic Looping Problems (pdf).
  • Nested Loop Problems (pdf)
  • Practice Boolean Operators
  • Old exams.

Chapter 1: Introduction

Topics

• Java sytax for creating a class, e.g. see HelloPrinter on p. 13
• What is a statement?
• How is a block of code specified (i.e. with braces)?
• Name of java file must be same as the java class.
• Printing output using System.out.println()
• Programming Conventions (Style guide):
  • files names begin with uppercase
  • method (function) names begin with lowercase
  • Blocks of code are indented, i.e. Code within braces is indented.
• What are compile vs run-time errors?

Chapter 2: Fundamental Data Types

Vocabulary

variable type constant magic number literal statement expression mod (remainder) function

declare initialize assignment statement operator operator precedence cast stepwise refinement

Topics

• Sample problems: Variables (pdf)
• Variables: What are they, how do you create, name, and initialize them?
• How many times can one declare a given variable? How many times can one set the value of a given variable?
• Types: What is a data type? Why do we have them? What are examples (int,float, boolean, String, etc.)
• When can we convert from one type to another? What is casting?
• Java Statements: What is a statement, expression, value?
• What is a "literal"?
• Assignment statement: What is its syntax?
• Doing Arithmetic
  • Operators - binary (+, -, /, *, %) , unary (-, ++, --)
  • Operator Precedence and when you must use parentheses
  • The Math class for functions such as sqrt, pow, etc. -
    Learn to use the javadoc api !
  • Conversion between numeric types.
• Magic numbers: What are they? Why are they a problem?
• Constants: What are they? Why do we have them?
• Comments: What are they? Why do we have them? What is their syntax?
• Common Pitfalls:
  • Forgetting to declare and/or initialize a variable.
  • Declaring a variable multiple times.
  • Using integer division when you don't mean to.
• Problem Solving techniques
  • Don't jump into coding too quickly. Understand problem, try example by hand, write pseudocode.
  • Stepwise refinement - break problem into a sequence of steps that lead to the full solution. Implement one step at a time, compiling (compile time errors) and testing your code (run time erros)
• Strings: What is a string? Look at String API (Javadoc).
• String methods (e.g. length, charAt, substring) and sytax for calling them, StringName.methodName(inputs_to_method). See p. 65-66
• String concatentation and escape sequences
• Math methods (e.g. min, max, pow, sqrt)
• Primitive types (int, float, etc) vs Object types (String, Scanner, etc):

Chapter 3: Decisions

Vocabulary

if statement condition and body if-else statement multi-way if-else nested if-else boolean value, expression

relational operator (<, >, <=, >=, ==, !=) boolean operators (&&, ||, !) lexicographic ordering (of Strings) De Morgan's Laws

Topics

• if-statement, if-else-statement
  • Syntax
  • Braces & indentation
  • Boolean values and variables:
    • What is a boolean variable? (boolean, true/false)
    • Relational operators – making number comparisons with <, >, <=. >=, ==, !=
    • Beware: relational operators are binary. For example, (2 < x < 5) is not a legal java expression.
    • What is a conditional expression?
    • Be careful!! Equality of Strings. Do not use ==. Instead, use myString1.equals(myString2)
• Multiway if-else
• Nested if, if-else statements - line up brackets so the structure is clear!
• Beware of where you put semicolons!
• Combining boolean expressions with AND (&&), OR (||), NOT (!) Write out truth tables.
  • Combining with relational operators
  • Practice Boolean Operators
• Strings and lexicographic ordering – compareTo operator
• Rules of Thumb & Common Errors:
  • Avoid duplication in branches
  • Dangling else problem
  • Syntax for condition ( 5 < x < 7 ) is NOT allowed! Need to use boolean operators.
• De Morgan's Law:
  • !(A && B) same as (!A) || (!B)
  • !(A || B) same as (!A) && (!B)
• Random numbers, e.g. rolling dice or dealing cards.

Chapter 4: Loops

Vocabulary

while-loop for-loop unwinding and hand tracing do-while-loop nested loop break Statement

Loop variable, initialization, condition, update; loop body sentinel value pseudorandom number counter, running total accumulator variable

Topics

• Sample problems: Basic Looping Problems (pdf), Nested Loop Problems (pdf)
• Components of any loop:
  • Loop variable - the variable that controls the looping
  • Loop variable initialization - the starting value of the loop variable.
  • Loop condition - this must be true for loop to continue
  • Loop variable update - how does loop variable change after each loop
  • Loop body - sequence of statements that are executed in the loop
• Types of loops:
  • while-loops - used when the number of repetitions can't be predicted ahead of time (indefinite)
  • for-loops - when you know precisely how many times you will loop (definite). Loop variable only defined within loop.
  • do-while-loops - checks condition at end; always executes the body at least once
  • Nested loops.
• Figuring out what is going on - Hand tracing, unraveling the loop
• Common Errors: infinite loops, off-by-one
• Sentinel values - the user controls when to stop
• Common Uses of Loops:
  • Entering a sequence of values.
  • Counting the number of items entered.
  • Accumulating (e.g. summing) values
  • Finding certain values (e.g. max or min)
  • Checking for correct user input