Data Types in C++

Definition of Data Types

A data type is the type of data a variable can hold. For example, a Boolean variable can have boolean data, and an integer variable can hold integer data.

While coding, we need to use different variables to store different information. Variables are just storage locations reserved for storing values. Therefore when you create the variable, you reserve some space in memory. You may want to store information for different data types, such as integers, floats, strings, and Boolean values. Memory is allocated based on the variable's data type. The amount of memory required depends on the data type.

For example,

score here is an int datatype variable. The variable score can only store 2-byte or 4-byte integers, depending on the compiler/system.

In C++, data types can be classified as follows:

1. Primitive/Built-in Datatypes
2. Derived Datatypes
3. Abstract/User-defined Datatypes

Primitive Data types in C++

Users can use the primitive data types to declare variables, and these are built-in data types in C++, for instance, float, bool, etc. Primitive data types present in C++ are defined below:

1. Integer

The keyword int can represent integer data types. The range of integers is -2147483648 to 2147483647, and they take up 4 bytes of memory.

For example,

data here is an integer data type variable. The variable data requires 2 or 4 bytes of memory space.

2. Character

The keyword char represent characters. It is 1 byte in size. Single quotes ' ' are used to enclose characters in C++.

For example,

ch here is a character datatype variable. This means that the variable requires 1 byte of memory space.

3. Boolean

The boolean data type's keyword is bool. True or false are the two possible values for the boolean data type. Boolean values are generally used in conditional statements and loops.

For example,

is_true here is a boolean data type variable. This means that the variable requires 1 byte of memory space.

4. Floating Point

float is the keyword used to hold floating-point numbers (decimals and exponentials). The float variable has a size of 4 bytes.

For example,

val here is a floating-point datatype variable. This means that the variable requires 4 bytes of memory space.

5. Double Floating Point

double is the keyword used to hold floating-point numbers (decimals and exponentials) with double precision. The double variable has a size of 8 bytes.

For example,

val here is a double floating-point datatype variable. This means that the variable requires 8 bytes of memory space.

6. Void or Valueless

The term void refers to something that has no worth. The void data type represents a valueless entity. Variables of the void type cannot be declared. It is only used for functions, not returning any data.

7. Wide Character

The wide-character wchar_t data type is similar to the char data type, but its size is 2 or 4 bytes rather than 1 byte. It's used to represent characters that take up more memory than a single char to represent.

For example,

w here is a wide-character datatype variable that has a value of 67 (L'C') and has a size of 4 bytes. This means that the variable requires 2 bytes or 4 bytes of memory space.

Derived Data types in C++

Derived Data Types are data types that are created by combining primitive or built-in datatypes. There are four different types of derived data types. These are :

1. Function

A function is a code segment or a block of code defined to accomplish a specific purpose. A function is often designed to spare the user from repeatedly writing the same lines of code for the same input. All the lines of code are combined into a single function that may be invoked from anywhere. Every C++ application includes a default function called main().The function also has a return type, which is used to specify the type of data the function would return when its execution is complete. The function's return type could be any data type, including the void, which states that there is no need to return anything once the execution of that function is complete.

Syntax:

Example:

Here, the return type of the sum function is an integer, and the function is used to calculate the sum of 2 numbers.

2. Array

An array is a set of elements that are kept in memory in a continuous manner and also have the same type of data present within the array. The purpose of an array is to store a lot of data in a single variable name and sequential order.

Syntax:

Example:

Here, we have defined an integer array of size 4, which can continuously store four integer variables in memory.

3. Pointer

Pointers are symbolic representations of addresses. Pointers store the addresses of the variables having the same datatype as that of the pointer. The size of the pointer is either 4 bytes or 8 bytes, no matter what the data type is. They enable programs to create and change dynamic data structures, as well as to imitate call-by-reference. In C/C++, its generic declaration looks like this:

Syntax:

Example:

point_int holds the address of a variable of an integer datatype.

4. Reference

When we declare a variable as a reference, it becomes an alternate name for an existing variable. By adding '&' to a variable's declaration, it can be declared as a reference.

Example:

Here ref becomes the reference to integer val, and now any changes in one would be automatically reflected in the other as they both represent the same memory location.

Abstract or User-Defined Data types in C++

The Abstract datatype, also known as user-defined data type, is a type of data defined by the user.

Examples of these are:

1. Class

A Class is a C++ building piece that leads to Object-Oriented programming. It's a user-defined data type with its own set of data members and member functions that can be accessed and used by establishing a class instance. A class defines the blueprint for a data type.

Example:

Output :

In the above example, the scaler is the name of the class. We can include the data members, which are the class variables. Similarly, member functions are added to the class; for example, print_name(), here is the member function, and student_name is the data member. Here, the student1 and student2 are the class scaler objects.

2. Structure

A structure datatype is a user-defined data type that combines objects of potentially different data types into a single type.

Example:

Here, different data types, such as an array of characters and integer data types, are combined to make a new data type according to the user's need.

3. Union

Union is similar to Structures as it is also used to combine the different types of data into a single user-defined data type. All members of a union have access to the same memory. In the below-shown example, we can combine the integer data type and the character data type into a single data type called test. In this case, as both the data types, integer, and character have different data sizes, we would take the larger data type as the size of the new user-defined data type test. We can see how changes in num are reflected in var if we adjust num.

Example:

Here, num and var share the same memory. Therefore, if we change any variables, the changes will automatically reflect in another variable.

4. Enumeration

In C++, an enumeration (or enum) is a data type that the user creates. It's primarily used to give integral constant names, making the program easier to comprehend and maintain. In enumeration, if we do not provide the integral values explicitly to the strings, then, in that case, the strings automatically start assigning the integral values starting from value 0, the same as the case of 0-based indexing.

Example:

Here, we have given the integer value 100 to be pass and 0 as fail; therefore, if we write,

Then, the value of res would automatically be 100.

5. Typedef defined DataType

The term typedef in C++ allows you to declare explicit new data type names. Using typedef does not create a new data class; instead, it gives an existing type a name. Because just the typedef statements would need to be updated, a program's portability might be improved by making minimal changes. By permitting descriptive terms for the standard data types, typedef can aid in self-documenting code.

Example:

Now we can use ll to define the long int data type in the code.

For Example,

Datatype Modifiers in C++

DataType modifiers can be used to change some of the core data types further. In C++, there are four modifiers. int, double, and char are the data types that can be modified using these modifiers. They are as follows:

1. Signed

2. Unsigned

3. Short

4. Long

The table below illustrates the variable type, the amount of memory required to hold the value in memory, and the maximum and lowest values stored in such variables. The below values may differ from one compiler to another. GCC 32 bit was used in the following values.

The code below will result in the correct size of various data types on your PC:

Code:

Output:

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• Keywords in C++.