Programming with C: Structs, Unions, and Constants

Name: Programming with C: Structs, Unions, and Constants
Author: Mike McMillan

Understand the functions of the common C data structures structs, unions, and constants

Preview the first lesson free — get full access to all 5 lessons.

Course: On-Demand

Hi, this is Mike McMillan and welcome back to this course on intermediate C programming. In this video, I'm going to introduce the concept of the struct or structure. So let's get started. A struct is a composite data type that allows you to store more than one value inside a single variable name. That's why we call it composite. So for example, without structs if I wanted to store information about a student, say their ID and their course grade, I'd have to have two separate variables. But with a struct, I can have one variable that has a field for the ID and a field for the grade. So let me demonstrate how that works. Struct definitions go up in the global section above or below int main, I always do mine above int main and any struct that you create is gonna start off with the keyword struct, followed by the name of the struct. In this case, I want to create a student so I'm gonna call my struct student, and then an open curly brace. And of course, code blocks puts a closing curly brace in. And then notice that it also includes a semicolon at the end. That's a little syntax for the compiler to recognize that this is a composite data type or a struct. So inside the struct are going to go what are called field declarations. So for example, I'm gonna write a simple student struct that has two fields, a field for the student ID and a field for the course grade. So a field declaration is simply declaring a variable. So there's my field declaration for the id, int id. Now I'm gonna come back and create another one for the grade. Just like that. You can use any legitimate data type as a field data type. So ints, doubles, chars, any of those data types can be used. You can also do something like this. If I wanted to store a set of grades rather than one grade I could also have an array inside there. Let me show you one more example. Here's an example of a name struct where we're going to have two char arrays, which are how you define strings in C, one for the first name and one for the last name. Again, the idea with the struct is that you could have more than one data type stored in a single variable name and in a separate video, I'm gonna show you how to create struct variables. But for now, we're just talking about how to create them. And the way create them is by using the keyword struct followed by the name of the struct. And then inside the body will be the declarations of the varying fields. You'll notice by convention that we capitalize the first letter of a struct. That way we can keep struct types separate from the other built-in data types, which are not capitalized. So that's how you create structs. And I want to thank you very much for watching this video.

Intermediate Provider : Mike McMillan 5 Lessons · 20m in Arabic, German, English, Spanish, French, Portuguese, Chinese

Course Description

Unlike many more modern programming languages, C does not have a wide variety of libraries for supplying advanced data structures. In these lessons, we’ll go over two other data structures you can use in C, the struct and the union.

We’ll go over how to define structs—special data structures that allow a programmer to create composite data types—how to create struct objects, how to add data to them, and how to use them in programs. You’ll also learn about unions, which allow one variable to hold more than one data type as a value. We’ll demonstrate how to create unions, how to assign data to them, how to access the data stored in a union, and what happens when you try to access a union's field when it’s not currently storing a value.

What You'll Learn

Define a new struct and create composite data types in C
Initialize struct objects and add data to them
Use structs to solve computing problems, including passing structs as function arguments
Create unions and assign data to them so one variable can hold more than one data type
Access data stored in a union, including what happens when accessing a field that is not currently storing a value
Create and use constants in C

Key Takeaways

Unlike many more modern programming languages, C does not have a wide variety of libraries for supplying advanced data structures.
A struct is a special data structure that allows a programmer to create composite data types.
A union allows one variable to hold more than one data type as a value.
The course covers what happens when you try to access a union's field when it is not currently storing a value.
Structs can be passed as function arguments within C programs.

Frequently Asked Questions

What does this C programming course cover?

It covers two data structures you can use in C: the struct and the union. You learn how to define structs, create struct objects, add data to them, use them in programs (including as function arguments), and how to create unions, assign data to them, and access the data stored in a union. It also covers creating and using constants.

What is the difference between a struct and a union as taught here?

A struct is a special data structure that lets a programmer create composite data types, while a union allows one variable to hold more than one data type as a value.

What skills does this course help build?

It builds skills in C (Programming Language), C Compilers, C Data Types, C-Based Programming Languages, Data Structures, and Modular Programming in C.

What lessons are included in this course?

The lessons are Creating Structs, Using Structs, Structs as Function Arguments, Creating and Using Unions, and Creating and Using Constants.

Why does C use structs and unions for data structures?

Unlike many more modern programming languages, C does not have a wide variety of libraries for supplying advanced data structures, so structs and unions are two data structures you can use in C.