1. EECE.2160 ECE Application Programming
Instructors:
Dr. Michael Geiger & Peilong Li
Spring 2016
Lecture 20
Arrays and functions

2. ECE Application Programming: Lecture 20
Lecture outline
Announcements/reminders
Program 6 due 3/28
Exam 2 in class 3/30
Will be allowed one double-sided 8.5” x 11” note sheet
Review
One-dimensional arrays
Two-dimensional arrays
Today’s lecture
Arrays and functions
4/21/2019
ECE Application Programming: Lecture 20

3. ECE Application Programming: Lecture 20
Review: arrays
Arrays: groups of data with same type
x[10] has 10 elements, x[0] through x[9]
Can also define with initial values
e.g. double list[] = {1.2, 0.75, };
Compiler will determine size of array from list
If initialization list has fewer values than size given, remaining values = 0
i.e. int list[5] = {1, 2, 3} same as
int list[5] = {1, 2, 3, 0, 0}
Must be sure to access inside bounds
You can access x[12] or x[-1], for example
Will access whatever’s at those locations
4/21/2019
ECE Application Programming: Lecture 20

4. ECE Application Programming: Lecture 20
Review: 2D arrays
Declared similarly to 1D arrays
Example (see below): int x[3][4];
Index elements similarly to 1-D arrays
Initialize: int y[3][4] =
{ {1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12} };
Typically used with nested for loops
Col. 0
Col. 1
Col. 2
Col. 3
Row 0
x[0][0]
x[0][1]
x[0][2]
x[0][3]
Row 1
x[1][0]
x[1][1]
x[1][2]
x[1][3]
Row 2
x[2][0]
x[2][1]
x[2][2]
x[2][3]
4/21/2019
ECE Application Programming: Lecture 20

5. Example: Working with 2-D arrays
Complete this program, which counts the # of negative values in each row of a 2-D array (assume the necessary #includes are done): #define NRows 3 // # of rows #define NCols 4 // # of columns int main() { double x[NRows][NCols] = // 2-D array { { 10, 2.5, 0, 1.5}, {-2.3, -1.1, -0.2, 0}, {10.5, -6.1, 23.4, -9.2} }; int negCnt[NRows] = {0}; // Initialize entire row count array to 0 int i, j; // Row and column indices /* INSERT CODE HERE--Visit every element in array x and count the number of negative values in each row */ // Now print the row counts for (i = 0; i < NRows; i++) printf(“Row %d has %d negative values.\n”, i, negCnt[i]); return 0; }
4/21/2019
ECE Application Programming: Lecture 20

6. ECE Application Programming: Lecture 20
Example solution
/* Code to be added to visit every element in array x and count the number of negative values in each row */ for (i = 0; i < NRows; i++) for (j = 0; j < NCols; j++) if (x[i][j] < 0) negCnt[i]++;
4/21/2019
ECE Application Programming: Lecture 20

7. Passing arrays to functions
Do not need to specify array size (for reasons I’ll explain shortly)
Compiler will actually ignore 1-D array size, even if you put it in prototype
Therefore cannot check array size inside function
Prototype typically has array name and brackets to indicate you’re dealing with array
e.g. int findAvg(int arr[ ], int n);
n = # elements in array
4/21/2019
ECE Application Programming: Lecture 20

8. ECE Application Programming: Lecture 20
Final notes
Next time (M 3/21)
Finish discussing arrays and functions
Character arrays and strings
Enjoy your break!
Reminders:
Program 6 due 3/28
Exam 2 in class 3/30
Will be allowed one double-sided 8.5” x 11” note sheet
4/21/2019
ECE Application Programming: Lecture 20