Slides: Structs, Unions, and Enums

class: title
# Structs, Unions, and Enums
## CSC 161 – February 17, 2026

---
# Agenda for Today
1. Department Events
2. Upcoming Work
3. Code Cleanup
4. Discussion
5. Lab
6. Wrap Up

---
# Department Events

## CS Table: Open Source and LLMs
.indent[
  Tuesday, February 17th at noon in JRC 224C  
]

## CS Extra: Tarski Lower Bounds from Multi-Dimensional Herringbones
.indent[
  Speaker: Reed Phillips, Purdue University  
  Thursday, February 19th at 4:15pm in Noyce 3821  
  Snacks available in the CS Commons at 4pm
]

You can find a complete list of token events and submit more at <https://tinyurl.com/csc161-tokens>.

---
class: section blue
# Upcoming Work

---
# Week 4 Lab Report
**Due:** Tonight by 10:00pm

See last week's class slides for the list of exercises you should submit to gradescope.

Make sure you follow the most recent code style requirements we've discussed in class.

---
# Week 5 Quiz
As usual, we'll have a quiz on Thursday.
The quiz will last 10 minutes, and will focus on:

1. Structures
2. Enums
3. Binary Integer Representation (unsigned only)

Signed integer and floating point representations **will not** appear on Thursday's quiz.

---
# Homework: Connect Four
**Due:** Thursday, February 26th

## Questions
_None so far_

If you need to work on the assignment from off campus you can access a MathLAN session by going to <https://remote.cs.grinnell.edu>.

---
class: section blue
# Code Cleanup

---
# Code Cleanup
How can we make this code better?

```c
char x[128];
fgets(x, 128, stdin);
printf("You typed %s\n", x);
```

---
class: section blue
# Discussion

---
# Discussion: Structs
**Items for think, pair, share:**

1. What is a `struct`, and what is one scenario where you might want to use one?

2. What makes structs and arrays different in C? Do they have any similarities?

3. Write down a definition for the type `struct rectangle`, which will represent a rectangle.
   For any given rectangle, we will need to know its width and height so we can compute its area.

---
# Discussion: Unions and Enums
**Items for think, pair, share:**

1. What is an `enum` and what might you use it for?

2. What is a `union` and how is it different from a `struct`?

3. What is one situation where you might use a `union`?

---
class: section blue
# Lab

---
class: section blue
# Wrap Up

---
# Wrap Up

## Lab Work
Submit the completed `connect-four-stats.c` and `unions.c` source files (parts A through C) with this week's lab report.

## Mentor Session
This week, our Wednesday mentor session will run from 8–9pm instead of the usual two hour block.

## Reading

- **Binary Representation of Integers in C** 
              
            
              
- **Floating Point Representation**