CS 112 Introduction to Programming

1
CS 112 Introduction to Programming

• Lecture 22
• Review
• Http//zoo.cs.yale.edu/classes/cs112/

2
Admin.

• Midterm one this evening
• Location DL 220 7-9 PM
• Office hours today
• 2-3pm (AKW 202)
• Another time slot before the exam to be posted
  on the class page

3
C Data Types
count
t4

• Value (simple) type
• int, char, double, etcA value type variable
  stores a value of the type of the variableint x
  45double y 45.12
• Reference type
• Class or arrayA reference variable stores a
  reference to an object or arrayA reference is a
  location in computers memory where the object
  or array itself is storedTime3 t1t1 new
  Time3(11, 45, 59)
• Time3 t2 t1Time3 t4 new Time3(1, 2,
  3)t2.SetTime(2, 2, 2)Time3.Count()int a1
  1, 2, 3int a2 a1

x
45
y
45.12
t1
t2
a1
a2
4
Simple Data Types

• range and precision of data types
• know what data type to use, e.g., assignment 1
  problem 1
• input/output of simple data types Parse()
  methods
• arithmetic operations
• Result depend on type
•  4/5 0 while 4.0/5 0.8 and (double)4/5 0.8
  4/(double)5 0.8 int x (int)Math.Round(
  (double)4/ 5 )
• data conversion
• implicit conversion, cast, see examples of
  lecture 5
• boolean operations
• operator precedence
• a summary of all operators can be found at Fig.
  7.2 or slides of lecture 18.

5
Flow of Control

• conditional statements
• if and if/else statements
• C ternary conditional operator
• switch statement
• loop statements
• while, do/while, and for statements
• break/continue statements
• writing, choosing, and understanding loop
  programs, e.g.
• loop-and-a-half idiom

6
Classes and Methods

• Using a class to create objects
• an object has state and behavior
• A class definition includes variable and method
  definitions
• A variable or method can be static or non-static
• A non-static variable also called an instance
  variable
• A non-static method is also called an instance
  method
• See StaticTest and other samples.
• A variable or method can be public or private
  (default is private)
• enforce encapsulation

7
Defining a Method

• Overloading and signature
• Compiler try the best match
• If multiple matches, find the best match
• If no direct match, if implicit conversion is
  allowed to match a method, use it.
• Variables that can be used in a method
• A static method
• class scope static variables
• Local variables (we also consider formal
  arguments as local variables)
• An instance method
• Class scope variables (instance or static)
• Local variables

8
Calling a Method

• Each time a method is called, the actual
  arguments in the invocation are copied into the
  formal arguments
• If a value type, then it is the value that is
  copied
• If a reference type, then it is the reference
  that is copied
• The formal argument and the actual argument are
  different variables, with different memory
  locations
• However, if an argument of a method is ref (or
  out), then the formal argument and the actual
  argument are aliases of each other, i.e. they
  share the same memory cell

9
Arrays

• array declaration and initialization
• Some examples of arrays command line, string
• some typical designs of using arrays, e.g., using
  array elements as counters