Which Data Type Should Be Used to Store a Telephone Number?


Heather Bennett

When it comes to storing telephone numbers in a database or programming language, choosing the right data type is crucial. The data type determines how the telephone number will be stored and what operations can be performed on it. In this article, we will explore the different data types commonly used to store telephone numbers and discuss their advantages and disadvantages.

String Data Type

String is a common data type used to store telephone numbers. Since telephone numbers consist of digits, dashes, and sometimes parentheses, they can be conveniently represented as a sequence of characters within a string.

Using a string data type allows for flexibility in storing various formats of telephone numbers, such as “(123) 456-7890” or “123-456-7890”. Additionally, string manipulation functions can be easily applied to format or validate the phone number.

However, there are some drawbacks to using strings. Firstly, it consumes more memory compared to other data types since each character requires storage space. Secondly, performing mathematical operations on a phone number stored as a string is not straightforward and may require additional parsing or conversion.


// Storing a phone number as a string
string phoneNumber = "(123) 456-7890";

Numeric Data Types

Numeric data types are another option for storing telephone numbers. They include integer and floating-point types such as int, long, or double. While these data types are typically used for mathematical calculations, they can also be suitable for storing phone numbers if certain conditions are met.

If the telephone number does not contain any non-numeric characters like dashes or parentheses and there is no need for formatting or validation operations, a numeric data type can be used. Numeric types are more memory-efficient than strings and allow for mathematical operations like addition or subtraction.

However, using numeric data types may limit the ability to store phone numbers in different formats or apply formatting functions directly to the data type.


// Storing a phone number as an integer
int phoneNumber = 1234567890;

Custom Data Types

In some cases, it might be beneficial to create a custom data type specifically designed for storing telephone numbers. This approach allows for encapsulating the phone number logic and providing additional functionality through methods or properties.

A custom data type can handle formatting, validation, and parsing operations internally, making it easier to work with telephone numbers throughout the codebase. It can also enforce specific rules and constraints related to phone number storage.

Creating a custom data type requires more effort upfront but can lead to cleaner and more maintainable code in the long run.


// Custom Phone Number class with formatting and validation
class PhoneNumber {
  private string number;
  public PhoneNumber(string phoneNumber) {
    // validate and format the phone number
    this.number = FormatPhoneNumber(phoneNumber);

  private string FormatPhoneNumber(string phoneNumber) {
    // implementation logic for formatting

  public void Call() {
    // implementation logic for making a call

// Storing a phone number using custom data type
PhoneNumber phoneNumber = new PhoneNumber("(123) 456-7890");


Choosing the appropriate data type for storing telephone numbers depends on various factors such as required functionality, memory efficiency, and code maintainability. Strings provide flexibility but consume more memory, while numeric types are efficient but limit formatting capabilities. Custom data types offer the most control and encapsulation but require additional development effort.

Consider the specific requirements of your application and choose the data type that best suits your needs for storing telephone numbers.

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