1. EECE.2160 ECE Application Programming
Instructors:
Dr. Lin Li & Dr. Michael Geiger
Spring 2019
Lecture 29
Structures (continued)

2. ECE Application Programming: Lecture 30
Lecture outline
Announcements/reminders
Program 7 due Wed, 4/24
Remaining programs
Program 8 to be due Friday, 5/3 (last day of classes)
Program 9 (extra credit) to be due during finals; will not accept late submissions
Today’s lecture
Structures as function arguments—examples
Nested structures
7/9/2019
ECE Application Programming: Lecture 30

3. Review: Structures and functions
Can pass structures to functions
int f(StudentInfo s);
Structures consume significant memory
Usually much more efficient to simply pass pointer
int g(StudentInfo *p);
Access structure through pointer: -> operator
Handles dereferencing and field access
Example: p->GPA = 3.0;
7/9/2019
ECE Application Programming: Lecture 30

4. Example: Structures and functions
Write the following functions that use the StudentInfo structure
Given a pointer to a single StudentInfo variable, print all of the student info to the screen using the following format:
Michael J. Geiger
ID #
GPA: 1.23
Given an array of StudentInfo variables and the size of the array, compute and return the average GPA of all students in the list
Prompt the user to enter 3 lines of input (using the format below), read the appropriate values into StudentInfo elements, and return a value of type StudentInfo
Format (user input underlined)
Enter name: Michael J. Geiger
Enter ID #:
Enter GPA: 1.23
7/9/2019
ECE Application Programming: Lecture 30

5. ECE Application Programming: Lecture 30
Example solution
void printStudent(StudentInfo *s) { printf(“%s %c. %s\n”, s->first, s->middle, s->last); printf(“ID #%u\n”, s->ID); printf(“GPA %.2lf\n”, s->GPA); }
7/9/2019
ECE Application Programming: Lecture 30

6. Example solution (cont.)
double avgGPA(StudentInfo list[], int n) { int i; double sum = 0; for (i = 0; i < n; i++) sum += list[i].GPA; return sum / n; }
7/9/2019
ECE Application Programming: Lecture 30

7. Example solution (cont.)
StudentInfo readStudent() { StudentInfo s; printf(“Enter name: ”); scanf(“%s %c. %s”, s.first, &s.middle, s.last); printf(“Enter ID #: ”); scanf(“%u”, &s.ID); printf(“Enter GPA: ”); scanf(“%lf”, &s.GPA); return s; }
7/9/2019
ECE Application Programming: Lecture 30

8. ECE Application Programming: Lecture 30
Nested structures
Structures can contain other structures:
typedef struct {
char first[50]; // First name
char middle; // Middle initial
char last[50]; // Last name
} Name;
Name sname; // Student name
unsigned int ID; // ID #
double GPA; // Grade point
} SINew;
7/9/2019
ECE Application Programming: Lecture 30

9. Nested structure accesses
Will need multiple dot operators to access field within nested structure
Given SINew s1;
s1.sname  Name structure within s1
s1.sname.middle  middle initial of name within s1
Structure pointer typically only to top-level structure
Given SINew *sp = &s1;
sp->sname  Name structure within s1
sp->sname.middle  middle initial of name within s1
7/9/2019
ECE Application Programming: Lecture 30

10. ECE Application Programming: Lecture 30
PE3 (Structures)
Given header files, main program
Complete specified functions
For the Name structure
void printName(Name *n): Print the name pointed to by n, using format <first> <middle>. <last>
void readName(Name *n): Prompt for and read a first, middle, and last name, and store them in the structure pointed to by n
SINew functions on next slide
7/9/2019
ECE Application Programming: Lecture 30

11. Today’s exercise (continued)
Given header files, main program
Complete specified functions
Name functions on previous slide
For the SINew structure
void printStudent(SINew *s): Print information about the student pointed to by s
void readStudent(SINew *s): Prompt for and read information into the student pointed to by s
void printList(SINew list[], int n): Print the contents of an array list that contains n StudentInfo structures
int findByLName(SINew list[], int n, char lname[]): Search for the student with last name lname in the array list. Return the index of the structure containing that last name, or -1 if not found
int findByID(SINew list[], int n, unsigned int sID): Search for the student with ID # sID in the array list. Return the index of the structure containing that last name, or -1 if not found
7/9/2019
ECE Application Programming: Lecture 30

12. ECE Application Programming: Lecture 30
Final notes
Next time
File I/O (Lecture 32)
Reminders:
Program 7 due Wed, 4/24
Remaining programs
Program 8 to be due Friday, 5/3 (last day of classes)
Program 9 (extra credit) to be due during finals; will not accept late submissions
7/9/2019
ECE Application Programming: Lecture 30