1. CS 1430: Programming in C++

2. Quiz 5–1: Arrays . . . . // DO_02: Declare an array myArray of
// type float of 50 elements.
float myArray[50]; ?

3. size elements (index: 0 to size -1)
float myArray[50];
int size;
// Read in the value of size.
cin >> size;
// Using a for loop to input values into the array.
// Assuming size is between 1 and 50 (30 in Quiz5-1).
for (int i = 0; i < size; i ++)
cin >> myArray[i];
size elements (index: 0 to size -1) ?
size

4. Using a Function to Read Data to an Array
The size (number of values to input) is known
Function Prototype
Function Name
InputToArray
Function Type
void
How to return an array?
Parameters
s[] : array of float
In, Out, InOut
OUT
size: int, number of values to read into s[] IN
// Parameters: (Out, In)
void InputToArray(float s[], int size);
// No &!

5. Passing Parameters
Basic Data Types (char, int, float, string, bool)
Pass by Value (without &)
Pass by Reference (with &)
Arrays (of any data type)
Always Pass by Reference
(Never &)
Why?
Save Space and Time for copying values

6. //--------------------------------------------------
// The function reads size float values into
// array s[], assuming size is positive
// and in the range.
// Parameters: (out, in)
void InputToArray(float s[], int size) {
for (int i = 0; i < size; i++)
cin >> s[i];
return; }
// What’s the value of size?

7. const int MAX_SIZE = 100;
void InputToArray(float s[], int size);
int main() {
int count;
float scores[MAX_SIZE], average;
cin >> count; // Assuming in the range
// Call function to input data to array scores[]
InputToArray(scores, count);
// No [] for array as actual parameter
// No type for any actual parameters
// Compute the average
return 0; }

8. Using a Function to Compute the Average
Function Prototype
Function name
ArrayAvg
Function type
float
Parameters
s[] : array of float
In, Out, InOut
size: int, number of elements of s[]
// Parameters: (In, In)
float ArrayAvg(const float s[], int size);
// Array is always passed by reference
// Use const for In array parameter
// No const for size

9. Using a Function to Compute the Average
Function Definition //
// The function computes and returns the average of all
// array elements of s[], assuming size is positive
// and in the range.
// Parameters: (In, In)
float ArrayAvg(const float s[], int size) {
float total;
total = 0;
for (int i = 0; i < size; i++)
total += s[i];
return total / size; }
// Compute average after the for loop.
// Not inside the loop!

10. const int MAX_SIZE = 100;
void InputToArray(float s[], int size);
float ArrayAvg(const float s[], int size);
int main() {
int count;
float scores[MAX_SIZE], average;
cin >> count;
InputToArray(scores, count);
// Function call: No type! No []!
average = ArrayAvg(scores, count);
cout << “The average score: ” << average;
return 0; }

11. Function Parameters
Basic Data Types (char, int, float, string, bool)
Pass by Value (without &)
In Parameters
Pass by Reference (with &)
Out and InOut Parameters
Arrays (of any data type)
Always Pass by Reference (Never &)
In Parameters: const

12. Lab5: 3 point by 5 pm Tuesday
Schedule
Quiz5-1
Due 10 PM Today
Quiz5-2
Due 10 PM Wednesday
Thursday: Lab6
Lab5: 3 point by 5 pm Tuesday
Program 3
Due 10 PM Tuesday

13. Quiz5-1
// DO_04: Input a number into the first element of myArray. // DO_05: Input a number into the last element of myArray. // DO_12: Assign the average of the 1st, 2nd and last array // elements of myArray to the second to last array element // of myArray. // DO_13: Complete the following statement to output // the second to last array element of myArray. // DO_14: Use a for loop to compute the largest value of the // first 15 elements of myArray and store the result in Max.
What’s the index? 49
to 48 48
0 to 14

14. Data Type double Any Questions?
Prog3
Data Type double Any Questions?