C Variables and Constants

Name: C Variables and Constants
Author: Mike McMillan

Learn how to implement the different C data types into your code

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Course: On-Demand

Hi, this is Mike McMillan and welcome back to this beginning course in C programming. In this lesson I'm going to show you how to declare variables and assign values to variables in C programs. So the way variables are declared is following this basic syntax template You have a data type followed by a variable name. Well, and actually also a semicolon. With that in mind, let's look at a couple of examples. So, here I'm declaring a variable name "salary" and I'm declaring it as an "int type" which means it's going to hold a whole number. Here, I'm declaring a variable ratio that will be double. Which means it's going to hold a double precision floating point number. And in this last example, I've created a variable or I've declared a variable named "letter" and it's going to hold a "char" or a single character. The way we assign data to a variable is via an assignment statement. And assignment statements have the following syntax where we had the variable name followed by the equal sign which is the assignment operator followed by an expression which can be either a literal value or it could be like an arithmetic expression and I'll show you some examples of that. Oops-we've already declared salary so I don't have to re-declare it. Write it out like so, so here I'm saying the variable salary gets the value thirty-thousand and you have to remember that the equal sign in this example is not expressing a quality, it's representing a assignment In other words, I'll say, gets or receives so that you don't get the idea that I'm saying that salary equals thirty-thousand, because actually at the time that the compiler looks at the variable salary it doesn't have anything in it yet. It's only after the statement is completed that the thirty-thousand is placed into the variable. Another example might be this one and here's an example of an expression. So 2.2 times 0.01 is an arithmetic expression, obviously and the compiler will evaluate that expression first to get a value and then assign that value to ratio. I misspelled it there. But, to back up just for a second In lots of ways, a literal thirty-thousand is an expression also because expressions evaluate to something. And in this case, a literal evaluates to itself whereas, this expression below evaluates to whatever 2.2 times 0.01 is. For a char example, here we assign the letter "C" to the variable letter. And again, char values are represented with single quotes. So we're saying that take the letter "C" actually, the ASCII value for the letter "C" and assign that to the variable letter. So to review, we have two different types of statements here. We have a-a variable declaration statement which consists of a data type, followed by a variable name. So we have int salary, double ratio char letter. So those are all variable declarations. And then in the second set, we have assignment statements where we have a variable, the assignment operator, and an expression. Which can either be a value, or a piece of data, or an arithmetic expression. All of these statements are all ended with semicolons. That's very important to remember, and keep in mind that leaving a semicolon out, will lead to an error in your program. So, that wraps up this lesson on declaring variables and assigning them values. And in the next lesson, we're going to talk about how you can perform this in one statement, to save a little bit of time.

Beginner Provider : Mike McMillan 4 Lessons · 17m in Arabic, German, English, Spanish, French, Portuguese, Chinese

Course Description

In this Variables and Constants course, we’ll cover the different data types C uses to work with numbers and text. These lessons will cover the fundamental data types for storing numbers, characters, and strings, including Int for whole numbers, Float for single-precision floating-point numbers, and Double for double-precision floating-point numbers. We’ll also explain Char, the data type C uses for individual alphabetic characters, which is stored as an integer value to make the language more efficient—C does not have a string type, but instead stores strings as arrays of characters.

These lessons also discuss why C doesn’t have a special constant for true or false values. C was designed to be an efficient programming language, and not having a dedicated Boolean type allows programs to run much more efficiently. This often causes confusion for programmers experienced with more modern languages, as these languages usually have a Boolean type for true and false values.

What You'll Learn

Create code using the three C numeric data types: Int for whole numbers, Float for single-precision floating-point numbers, and Double for double-precision floating-point numbers
Explain how C uses the Char data type to store individual character values as integer values
Understand how Boolean data is represented in C and why C has no dedicated true/false constant
Declare and assign values to variables, and initialize new variables
Declare and use constants in C
Write arithmetic statements in C

Key Takeaways

C uses Int for whole numbers, Float for single-precision floating-point numbers, and Double for double-precision floating-point numbers.
C stores the Char data type as an integer value to make the language more efficient, and it does not have a string type, instead storing strings as arrays of characters.
C does not include a dedicated Boolean type for true and false values, which allows programs to run more efficiently.
The absence of a Boolean type often confuses programmers experienced with more modern languages that usually have one.
The course covers declaring and assigning values to variables, initializing new variables, declaring and using constants, and writing arithmetic statements.

Frequently Asked Questions

What does this course cover?

It covers the different data types C uses to work with numbers and text, including the fundamental data types for storing numbers, characters, and strings: Int, Float, Double, and Char. It also explains why C does not have a special constant for true or false values.

Which numeric data types are taught in this course?

The course covers the three C numeric data types: Int for whole numbers, Float for single-precision floating-point numbers, and Double for double-precision floating-point numbers.

How does C handle characters and strings according to this course?

C uses the Char data type for individual alphabetic characters, stored as an integer value to make the language more efficient. C does not have a string type and instead stores strings as arrays of characters.

Why does C not have a Boolean type?

C was designed to be an efficient programming language, and not having a dedicated Boolean type for true and false values allows programs to run much more efficiently.

What lessons are included in this course?

The lessons are: Declaring and Assigning Values to Variables; Initializing New Variables; Declaring and Using Constants; and Arithmetic Statements.