Announcements

1
Announcements

• Starting next week class 6-8 on Thursday
• Homework 1 on the web
• Due January 29 next class meeting
• Homework policy
• No late assignments
• Graded out of 10 points
• Receive 5 points for turning it in

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Lecture 2
3
Topics of this lecture

• Introduce first program
• Explore inputs and outputs of a program
• Arithmetic using C
• Introduce the conditional statement

4
General Notes About Cand This Book

• Book geared toward novice programmers
• Stress programming clarity
• C and C are portable languages
• Portability
• C and C programs can run on many different
  computers
• Compatibility
• Many features of current versions of C not
  compatible with older implementations

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Introduction to C Programming

• C language
• Facilitates structured and disciplined approach
  to computer program design
• Following several examples
• Illustrate many important features of C
• Each analyzed one statement at a time
• Structured programming
• Object-oriented programming

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A Simple ProgramPrinting a Line of Text

• Comments
• Document programs
• Improve program readability
• Ignored by compiler
• Single-line comment
• Begin with //
• Preprocessor directives
• Processed by preprocessor before compiling
• Begin with

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Basics of a Typical C Environment

• Input/output
• cin
• Standard input stream
• Normally keyboard
• cout
• Standard output stream
• Normally computer screen
• cerr
• Standard error stream
• Display error messages

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fig01_02.cpp(1 of 1)fig01_02.cppoutput (1 of
1)

• 1 // Fig. 1.2 fig01_02.cpp
• 2 // A first program in C.
• 3 include ltiostreamgt
• 4
• 5 // function main begins program execution
• 6 int main()
• 7
• 8 stdcout ltlt "Welcome to C!\n"
• 9
• 10 return 0 // indicate that program
  ended successfully
• 11
• 12 // end function main

Welcome to C!
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A Simple ProgramPrinting a Line of Text

• Standard output stream object
• stdcout
• Connected to screen
• ltlt
• Stream insertion operator
• Value to right (right operand) inserted into
  output stream
• Namespace
• std specifies using name that belongs to
  namespace std
• std removed through use of using statements
• Escape characters
• \
• Indicates special character output

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A Simple ProgramPrinting a Line of Text
Make some modifications to First Program
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Another Simple ProgramAdding Two Integers

• Variables
• Location in memory where value can be stored
• Common data types
• int - integer numbers
• char - characters
• double - floating point numbers
• Declare variables with name and data type before
  use
• int integer1
• int integer2
• int sum
• Can declare several variables of same type in one
  declaration
• Comma-separated list
• int integer1, integer2, sum

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Another Simple ProgramAdding Two Integers

• Variables
• Variable names
• Valid identifier
• Series of characters (letters, digits,
  underscores)
• Cannot begin with digit
• Case sensitive

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Another Simple ProgramAdding Two Integers

• Input stream object
• gtgt (stream extraction operator)
• Used with stdcin
• Waits for user to input value, then press Enter
  (Return) key
• Stores value in variable to right of operator
• Converts value to variable data type
• (assignment operator)
• Assigns value to variable
• Binary operator (two operands)
• Example
• sum variable1 variable2

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fig01_06.cpp(1 of 1)

• 1 // Fig. 1.6 fig01_06.cpp
• 2 // Addition program.
• 3 include ltiostreamgt
• 4 // function main begins program execution
• 5 int main()
• 6 int integer1 // first number to be
  input by user
• 7 int integer2 // second number to be
  input by user
• 8 int sum // variable in which sum
  will be stored
• 9
• 10 stdcout ltlt "Enter first integer\n"
  // prompt
• 11 stdcin gtgt integer1
  // read an integer
• 12
• 13 stdcout ltlt "Enter second integer\n"
  // prompt
• 14 stdcin gtgt integer2
  // read an integer
• 15
• 16 sum integer1 integer2 // assign
  result to sum
• 17 stdcout ltlt "Sum is " ltlt sum ltlt
  stdendl // print sum
• 18
• 19 return 0 // indicate that program
  ended successfully

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Microsoft Visual C numeric data types
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Microsoft Visual C numeric data types
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Memory Concepts

• Variable names
• Correspond to actual locations in computer's
  memory
• Every variable has name, type, size and value
• When new value placed into variable, overwrites
  previous value
• Reading variables from memory nondestructive

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Memory Concepts

• stdcin gtgt integer1
• Assume user entered 45
• stdcin gtgt integer2
• Assume user entered 72
• sum integer1 integer2

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Effect of Several Assignments

• What are the values of a and b after all
  statements are executed?
• int a 1
• int b
• b a
• a 2
• a 2, b 1

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Arithmetic

• Arithmetic calculations
• Multiplication
• /
• Division
• Integer division truncates remainder
• 7 / 5 evaluates to 1
• Modulus operator returns remainder
• 7 5 evaluates to 2

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Arithmetic

• Rules of operator precedence
• Operators in parentheses evaluated first
• Nested/embedded parentheses
• Operators in innermost pair first
• Multiplication, division, modulus applied next
• Operators applied from left to right
• Addition, subtraction applied last
• Operators applied from left to right

X 7 4 / 2 (3 ( 4 3) 5) 2 3
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Decision Making Equality and Relational Operators

• if structure
• Make decision based on truth or falsity of
  condition
• If condition met, body executed
• Else, body not executed
• Equality and relational operators
• Lower precedence than arithmetic operators
• Equality operators
• Same level of precedence
• Relational operators
• Same level of precedence
• Associate left to right

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Decision Making Equality and Relational Operators
Notice (not )
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Decision Making Equality and Relational Operators

• using statements
• Eliminate the need to use the std prefix
• Allow us to write cout instead of stdcout
• To use the following functions without the std
  prefix, write the following at the top of the
  program
• using stdcout
• using stdcin
• using stdendl

Look at example program
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Thinking About Objects Introduction to Object
Technology and the Unified Modeling Language

• Object orientation
• Natural way to think about the world and to write
  computer programs
• Attributes - properties of objects
• Size, shape, color, weight, etc.
• Behaviors - actions
• A ball rolls, bounces, inflates and deflates
• Objects can perform actions as well
• Inheritance
• New classes of objects absorb characteristics
  from existing classes
• Information hiding
• Objects usually do not know how other objects are
  implemented

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Thinking About Objects Introduction to Object
Technology and the Unified Modeling Language

• Abstraction - view the big picture
• See a photograph rather than a group of colored
  dots
• Think in terms of houses, not bricks
• Class - unit of programming
• Classes serve as a Blueprint" of objects
• Objects are created from a class
• Classes contain functions
• Used to implement behaviors
• Classes contain data
• Used to implement attributes
• Classes are reusable

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Thinking About Objects Introduction to Object
Technology and the Unified Modeling Language

• Unified Modeling Language (UML)
• Used to model object-oriented systems and aid
  with their design
• Complex, feature-rich graphical language