More on Input Output

1
More on Input Output

• Input Stream A sequence of characters from an
  input device (like the keyboard) to the computer
  (the program running).
• Output Stream A sequence of characters from the
  computer (the program running) to an output
  device (like the monitor).
• Standard Input Device a reference to the
  keyboard.
• Standard Output Device A reference to the
  monitor.

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More on Input Output

• The include statements are also called headers
• The header include ltiostreamgt includes the
  standard streams to the standard output and
  standard input devices as long as we have the
  statement
• namespace std or the alternative
• stdcout
• stdcin

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More on Input Output

• The symbol gtgt stands for extraction operator.
• It is a binary operator
• The left operand is a stream and the right
  operand is a memory location.
• i.e
• double payRate
• cingtgtpayRate
• The computer inputs the number typed on keyboard
  and stores it in memory location identified as
  payRate.

4
Selection (if-then-else)

• Programming Has 3 Types of Control
• Sequential (normal) Control of Execution
  Proceeds One after the Other
• Selection (if-then-else) Control Proceeds
  Dependent on Conditions
• Iteration (looping) Control Repeated until
  Condition Met

5
C if Statement Syntax

• Syntax
• if (condition) statement
• If Condition Is True, Statement Is Executed
• If Condition Is False, Statement Is Not Executed
• If Multiple Actions Are Required for Statement, a
  Compound Statement Must Be Used
• if (condition)
• statement
• statement

6
Conditional Operators

• Relational Operators lt , gt , gt , lt
• Equality Operators , !

7
Selection Examples

• if (age lt 30)
• cout ltlt You are very very Young ltlt endl
• if (grade A)
• cout ltlt Congratulations! ltlt endl
• if (grade ! F)
• cout ltlt You passed! ltlt endl

8
else Statement

• Syntax
• if (condition)
• statement(s) //condition true
• else
• statement(s) //condition false

9

if-else Example

• if (myGrade gt 60)
• cout ltlt You passed! ltlt endl
• else
• cout ltlt How about them Cubs? ltlt endl

10
Compound Statements

• Compound Statement One or More Statements within
  a Set of Curly Braces
• Must Use Compound Statement if More than One
  Statement Is Supposed to be under Control of if
  or else Conditional
• Include Curly Braces after if so if other
  Statements Are Added in Future, Curly Braces Are
  Already There

11
Nested if Statements

• if (myGrade gt 80)
• if (myGrade gt 90)
• cout ltlt You have an A! ltlt endl
• else
• cout ltlt You have a B! ltlt endl
• else
• cout ltlt Well give you a C. ltlt endl

12
if/else (Cascaded)

• Sequence of if/else Statements
• Example
• if (myGrade gt 90)
• cout ltlt A! ltlt endl
• else
• if (myGrade gt 80)
• cout ltlt B! ltlt endl
• else
• if (myGrade gt 70)
• cout ltlt C! ltlt endl
• else
• cout ltlt Oh-oh! ltlt endl

13
Boolean Type

• A Boolean Value Is One of Either True or
  False
• In C, Type bool
• Example
• bool done false
• . . .
• if (currentLetter Z)
• done true
• else
• done false
• if (done)
• return(0)
• . . .

14
Boolean Type

• if/else Conditionals Must Evaluate to True or
  False, and Are Therefore Called Boolean
  Expressions
• In C, Any Non-Zero Value Is Considered True
  Any Expression Evaluating to Zero Is Considered
  False

15
Logical Operators

• A Logical Operator Is One Used to Further Specify
  True or False in an Expression
• Connects Two or More Expressions Together
• Is Logical AND
• Is Logical OR
• Both Operands Must Be True for Entire
  Expression to Be True
• Only One (or Both) of the Operands Must Be
  True for Entire Expression to Be True

16
Logical Operators

• if (numStudents gt MIN numStudents lt MAX)
• classRun true
• if (numStudents gt MAX numInstructors 0)
• classRun false

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Operator Precedence

• ()
• ! (not)
• , /,
• , -
• lt, lt, gt, gt (Relational Operators)
• , ! (Equality Operators)
• (Logical AND)
• (Logical OR)
• (ASSIGNMENT)

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Order of Operations

• Precedence Level of Importance of Operations
• Multiplicative Operators Have Higher Precedence
  than Additive Operators
• , /, Higher
• , - Lower
• Associativity Order of Operation for Equal Level
  Precedence
• Most Operators Have Left-to-Right Associativity
• Use Parentheses to Force Differing Precedence of
  Operations

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Multiple Logical Operators

• if ( num1 gt MAX num2 0 num3 0)
• cout ltlt num1 is MAX or something is 0
• cout ltlt I think.. ltlt endl

20
Switch Statements

• Also Called Switch/Case Statement
• Just Case in Other Languages
• Selects Among Several Different Actions
• Can Only Select from Integer or Character
• If an Integer Value Is Matched, Statements under
  Control of that Case Block Are Executed

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Switch/Case Example

• int numPassengers
• cout ltlt Enter Passengers
• cin gtgt numPassengers
• switch(numPassengers)
• case 2
• rate BASERATE 0.80
• break
• case 4
• rate BASERATE 0.75
• break
• case 5
• rate BASERATE 0.55
• break
• default
• rate BASERATE
• break

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Switch Case Example

• char menuItem
• cout ltlt "Enter Menu Selection "
• cin gtgt menuItem
• switch(menuItem)
• case 'O'
• / code to do ordering goes here/
• break
• case 'C'
• / code to do checkout goes here/
• break
• default
• cout ltlt Unknown option ltlt endl
• break

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Announcements

• Exam 1 Tuesday July 14.
• 25 minutes
• 10 of Total Grade
• Covers Everything through Lectures 03 and o4
• All Terms (Underlined Items)
• Variable Declaration, Initialization, and
  Assignment
• Constant Declaration
• Expressions
• Operators
• Input (cin) and Output (cout)
• if/else and else if selections
• Logical Operators
• Switch