Exam 2

1
Exam 2

• EXAM 2 Tuesday July 28th!!!
• 25 of Final Grade
• Know
• loops, switch/case
• Files (.open(), gtgt and ltlt, .close() )
• Input Failure (cin, cin.clear(), cin.ignore())

2
To Read or Write from a File

• Declare the File Stream Object Name
• Associate a File Name with the File Stream Object
  by Opening the File
• Read or Write to the File using ltlt or gtgt
  Operators
• Close the File

3

• include ltiostreamgt
• include ltfstreamgt
• include ltstringgt
• using namespace std
• int
• main()
• ifstream input
• int loops, integer, i
• float decimal
• string name
• input.open("mydata.txt")
• input gtgt loops
• for(i 0 i lt loops i)
• input gtgt integer
• input gtgt decimal

mydata.txt file 5 8 9.3 Jon 6 14.335 Bill 0
35.67e9 Mary -23 -4.55 Smith -3 -4e3 xyz
Output
8 9.3 Jon 6 14.335 Bill 0 3.567e010 Mary -23
-4.55 Smith -3 -4000 xyz
4
Functions
displayVals() cout ltlt cout ltlt
cout ltlt return /back to where
we left off /
int main() displayVals()
displayVals() displayVals()
return(0)
5
Functions

• Function A Discrete Piece of Code that Performs
  a Specific Operation or Task
• Named with a Descriptive Identifier
• Called from main() or Another Function
• When Called, Program Control (Execution) Is
  Transferred to the Function
• Function Performs Required Tasks, and then
  Possibly Returns a Value
• After Return from Function, Control Returns to
  the Statement Following the Function Call

6
Function Attributes

• Function Name Identifier Used to Call Function
• Function Parameter(s) or Argument(s) Value(s)
  Passed into Function for Use by Function Code
• Function Return Value Value Returned by Function
  Back to Calling Function

7
Function Parameters (Arguments)

• May Pass as Many Parameters as Necessary to
  Function
• A Copy of the Value of the Parameter Is Passed to
  the Function
• Changing the Value of the Parameter in the
  Function Does Not Affect the Value of the
  Original Variable
• This Is Called Pass-by-Value

8
Declaring a Function

• Function Prototype Declaring a Function and How
  It Is Called Syntactically
• Used by the Compiler to Signal Syntax Errors
• Pseudocode Example
• return_type function_name(parameter_type
  parameter_name)
• Example
• double calculate_avg(int totOfItems, int
  numItems)

9
Functions Return Values

• Functions Are Typed According to Their Return
  Values void, int, double, etc.
• Functions Are Declared by Function Prototypes
  (Declarations) Found Above main()
• Function Returns a Value to Calling Function via
  return Statement
• Standard Functions (e.g., Those in STL) Have
  Function Prototypes in Header Files

10
Function Attributes

• include ltiostreamgt
• using namespace std
• void printNum(int) // function prototype
• main()
• int myNumber 7
• printNum(myNumber) // function call
• printNum(9)
• // begin function definition
• void
• printNum(int numToPrint)
• cout ltlt numToPrint

11
Another Function Example

• include ltiostreamgt
• using namespace std
• double calcAverage(int total, int numItems)
• main()
• int allGrades 974, numStudents 10
• double avgGrade 0.0
• avgGrade calcAverage(allGrades,numStudents)
• cout ltlt avgGrade ltlt endl
• double
• calcAverage(int total, int numItems)
• return (double) total / numItems

12
What If?

• Write a program that prompts for the names and
  locations of 1000 employees. Store the
  information in the program for later use.

13
Program for Previous

• string empName1, empName2, empName3,
• string empLocation1, empLocation2,
• cout ltlt Enter employee name 1
• cin gtgt empName1
• cout ltlt Enter Employee name 2
• cin gtgt empName2
• //Can we use a loop?

14
Arrays

• Syntax
• type variableNamesize
• Memory Is Set Aside for size Items of type
• Each Variable Location in Array Is Accessed by
  Offsetting into the Array with an Integer
  Expression
• Legitimate Offsets Are 0 to size-1
• Example lastname0 H

15
Array Example

• char lastname100
• lastname0 H
• lastname1 a
• lastname2 \0
• cout ltlt lastname0
• cout ltlt lastname

16
Array Example

• int values15
• values0 150
• values1 78
• values2 16
• cout ltlt values0
• values3 values0 6

17
Array Example

• const int ARRAY_SIZE 100
• int offset
• int numArrayARRAY_SIZE
• for(offset 0 offset lt ARRAY_SIZE offset)
• numArrayoffset 0

18
Array Example
const int ARRAY_SIZE 10 int offset, sum 0,
average int numArrayARRAY_SIZE for(offset
0 offset lt ARRAY_SIZE offset) cout ltlt
Enter Score ltlt offset ltlt cin gtgt
numArrayoffset for(offset 0 offset lt
ARRAY_SIZE offset) sum sum
numArrayoffset average sum / ARRAY_SIZE
19
Initializing Arrays

• int
• main()
• char cArray35 'a', 'b', 'c'
• int iArray 1, 2, 3, 4
• int iArray210 10, 13, 15, 17
• double dArray 3.4, 5.67e4
• double dArray15 6.7, 7.8, 9.5

20
Initializing string Arrays

• include ltstringgt
• using namespace std
• int
• main()
• string sArray "one", "two", "three"
• cout ltlt sArray0

21
Two Dimensional Arrays

• char cArray1020
• int iArray10050
• cArray00 a
• cArray01 b
• cArray919 x
• iArray00 99
• iArray15 135
• iArray9949 0

22
Exam 2

• EXAM 2 Tuesday July 28th!!!
• 25 of Final Grade
• Know
• loops, switch/case
• Files (.open(), gtgt and ltlt, .close() )
• Input Failure (cin, cin.clear(), cin.ignore())