## C Programming For Beginners - Data Types

written by: Noel Kalicharanโขedited by: J. F. Amprimozโขupdated: 12/19/2008

In this article, we discuss the concept of data typesโa fundamental building block of almost all programming languages. The most common data types are numbers and strings. Each data type defines constants of that type.

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### Data Types

Every day we meet names and numbersโat home, at work, at school or at play. A personโs name is a type of data; so is a number. We can thus speak of the two data types called โnameโ and โnumber.โ In the statement:

Mimi bought 3 dresses for \$199.95

we can find:

• an example of a name: Mimi;
• two examples of numbers: 3 and 199.95

Usually, we find it convenient to divide numbers into two kinds:

(1) whole numbers, or integers;

(2) numbers with a decimal point, so-called real or floating-point numbers.

In the example, 3 is an integer and 199.95 is a real number.

Exercise: Identify the data typesโnames, integers and real numbersโin the following:

(a) Michaelโs scoring average was 25.25 with a highest score of 45.

(b) Abigail, who lives at 41 Third Ave, worked 36 hours at \$11.50 per hour.

(c) In his 8 subjects, Richardโs average mark was 68.5.

Generally speaking, programs are written to manipulate data of various types. We use the term numeric to refer to numbers (integer or floating-point). We use the term string to refer to non-numeric data such as a name, address, job description, title of a song or vehicle number (which is not really a number as far as the computer is concernedโit usually contains letters, e.g. PBN8652).

Programming languages in general, and C in particular, precisely define the various types of data which can be manipulated by programs written in those languages. Integer, real (or floating-point), character (data consisting of a single character such as 'K' or '%') and string data types are the most common.

Each data type defines constants of that type. For example:

• some integer constants are 3, -52, 0 and 9813;
• some real (or floating-point) constants are 3.142, -5.0, 345.21 and 1.16;
• some character constants are 't', '+', '8' and 'R';
• some string constants are "Hi there", "The Art of Computer Programming" and "C World".

Note that, in C, a character constant is delimited by single quotes and a string constant is delimited by double quotes.

When we use a variable in a program, we have to say what type of data (the kind of constants) we intend to store in that variableโwe say we must declare the variable. It is usually an error if we declare a variable to be of one type and then attempt to store a different type of value in it. For example, it would be an error to attempt to store a string constant in an integer variable.

Upcoming articles will show you how declare and use data types to create programs which solve problems.

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### References

Reference text: C Programming - A Beginner's Course