1. EECE.2160 ECE Application Programming
Instructor:
Dr. Michael Geiger
Fall 2018
Lecture 30
Structures review

2. ECE Application Programming: Lecture 30
Lecture outline
Announcements/reminders
Program 5 regrades due today
Program 6 late penalties—last day for -1 penalty
Late penalties capped at -1 between Tuesday, 11/20 and Monday, 11/26
Penalties begin increasing again Tuesday, 11/27
Program 7 due Tuesday, 12/4
Today’s lecture: Structures ... again
An attempt to tie together everything we’ve covered about structures into one lecture
7/16/2019
ECE Application Programming: Lecture 30

3. Working with structures
Can rarely work with entire structure
Assignment only—that’s it
Work with individual member(s)
Must eventually deal with built-in types
Different modes of access for
Single structure variable  dot operator
Pointer to structure variable  arrow operator
Let’s discuss how and why …
7/16/2019
ECE Application Programming: Lecture 30

4. ECE Application Programming: Lecture 30
Structures vs. Arrays
Arrays
Pro: simple access (location- or index-based)
Con: doesn’t support multiple data types
Structures
Pro: more flexibility in data types
Con: complex access to members (name-based)
Complexity of access due to memory layout
7/16/2019
ECE Application Programming: Lecture 30

5. ECE Application Programming: Lecture 30
Dot operator
Used with single structure variable
Must specify specific instance of new data type
General form: <var name>.<member name>
Examples (to be handwritten):
7/16/2019
ECE Application Programming: Lecture 30

6. ECE Application Programming: Lecture 30
Pointers
Why are pointers useful?
Primarily as pointer arguments
Allow function to modify data declared outside
Why else are structure pointers useful?
Hint: how are arrays always passed to functions?
Saves time and space to pass structs by address
Use arrow operator—does work of
Pointer dereferencing
Member selection (dot operator)
7/16/2019
ECE Application Programming: Lecture 30

7. 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;
7/16/2019
ECE Application Programming: Lecture 30

8. 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
7/16/2019
ECE Application Programming: Lecture 30

9. ECE Application Programming: Lecture 30
Final notes
Next time
PE3: Structures (no, really)
Reminders:
Program 5 regrades due today
Program 6 late penalties—last day for -1 penalty
Late penalties capped at -1 between Tuesday, 11/20 and Monday, 11/26
Penalties begin increasing again Tuesday, 11/27
Program 7 due Tuesday, 12/4
7/16/2019
ECE Application Programming: Lecture 30