# Constants – C Programming language

|In order to construct a statement in C programming we need to combine certain keywords, variables and constants which is understandable for the C Compiler. In this tutorial, we will have a look at the C Constants. **Constants** are values or entities that do not change their value in the course of the program, unlike variables that are susceptible to changes according to the programmers need.

### Classification of Constants

The Constants in C can be classified as follows:

- Primary Constants
- Secondary Constants

These sections can further be divided into sub sections as shown in the figure below:

Here are the constants that we use in our codes. Let us see how we construct and use these constants.

For now we will have a look at the Primary Constants.

### Integer Constants

** Integer Constants** are the numbers that come under these categories

- Decimal (Base 10).
- Octal (Base 8)
- Hexadecimal (Base 16)

Have a look at the rules that guide the construction of Integer Constants:

- It should not have any floating point.
- Integer constants should have at least one digit.
- It can have a positive or negative sign. In case it doesn’t have any sign it is taken as a positive integer.
- No blank spaces or commas are allowed in an integer constant.

Another important note for integer constant is it’s range. For *Visual Studio* or *gcc* compilers, the range is **-2147483648** to **+2147483647**. For *Turbo C* or *Turbo C++* the range is **-32768** to –**32767**. This range basically depends on the type of compiler i.e. whether it is a 32 bit compiler or a 64 bit.

**Eg:** 257, +563,-3245,-56

### Real Constants

**Real Constants** also known as **Floating point Constants** are numbers that have a whole number followed by a decimal point followed by the fractional number. The real constants can be expressed in two forms:

- Fractional Form
- Exponential Form

Have a look at the rules that guide the construction of Real Constants in Fractional Form:

- It should have a floating point.
- It should have at least have one digit.
- It can have a positive or negative sign. In case it doesn’t have any sign it is taken as positive.
- No blank spaces or commas are allowed.

**Eg:** 546.236, +453.89, -22.564

In case the value we are dealing with is too small like **0.00003** or too big like **300000**, we can use the * exponential form* to express these constants as

**3.0e-5**and

**3.0e5**. The part before the

**‘e’**is known as

*mantissa*and the part after the

**‘e’**is known as

*exponent*. Have a look at the rules that guide the construction of Real Constants in Exponential Form:

- The mantissa and the exponential part should have a letter
**‘e’**between them. - The exponent should have at least one digit.
- It can have a positive or negative sign. In case it doesn’t have any sign it is taken as positive.

The range of Real constants in Exponential form is **-3.4e38** to **3.4e38**.

**Eg:** 5.6e9, +2.0e-7, -5.6e+8, -7.8e-5.

### Character Constants and String Constants

A** Character Constant** is a single alphabet, digit or special character enclosed within *‘single quotes’*.

Have a look at the rules that guide the construction of Character Constants :

- Should be enclosed within single quotes.
- The inverted commas should point to the left.
- It can have only one character, digit or special character.

**Eg:** ‘A’, ‘f’, ‘4’

A **string constant** is a combination of alphabets, digits and special characters enclosed within *“double quotes”*. Have a look at the rules that guide the construction of String Constants:

- Should be enclosed within double quotes.
- It can be of any length.
- It ends with a null character assigned to it by the compiler.

**Eg:** “Welcome to Codingeek”, “Good to see you”, “8 apples”, “learning is fun”.

*Thats all for now in constants. Hope you like the tutorial. Do come back for more because learning paves way for a better understanding.*

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*Happy coding!! *