Home TechnologyTools What’s the Difference Between Null and Nullptr in C++? (Detailed)

What’s the Difference Between Null and Nullptr in C++? (Detailed)

by Logan
A man coding on his laptops.

“Nullptr” is considered a keyword that depicts zero as an address, whereas “Null” is the value Zero as an integer.

If you’re a programmer, you might know how important it is to understand computer languages to code better. But sometimes, it can just be a bit confusing, and you might get mixed up between two things.

Similar is the case for Null and Nullptr in C++ Language. Let me tell you what these two terms mean and their functions to help you understand their difference and their usage.

Let’s dive right in!

What are Computer Languages?

Computer languages can be defined as code or syntax used to write programs and specific applications.

Basically, it’s a formal language used to communicate with computers. In the same way, different countries have different languages that help people share thoughts, so do computers.

These are invented to understand the computer’s programming and work on them. In general, computer language can be classified into three main categories:

  • Assembly language
    This is considered a low-level language used for microprocessors and multiple other programmable devices. It’s a second-generation language. It’s known for writing an operating system and writing different desktop applications.
  • Machine language
    This native language is a first-generation language. It’s called machine code or even object code, having a set of binary digits 0 and 1. These digits are understood and read by a computer system that interprets them quickly.
  • High-level language
    This was established due to portability issues in the older languages. The code couldn’t transfer this meant code was written on one machine. This language is easy to understand and is also very user-friendly.

The portion of the language that a computer understands is known as “binary.” On the other hand, the translation of the programming language into binary is known as “compiling.”

In short, programming languages allow people to give instructions to computers so that they can read and execute them. Each computer language has its distinct features, from C language to python.

These languages make it easier and quicker for computers to process large and complex data more efficiently. There are several programming languages in the world today. A few of these include Java, Python, HTML, C, C++, and SQL.

What’s a C++ Language?

C++ language is one of the world’s most popular programming languages. You’ll find this language in operating systems, graphical user interfaces, and embedded systems in today’s world.

It’s a cross-platform language that is used to create high-performance applications. C++ language was established by Bjarne Stroustrup, who’s also responsible for creating the C language. As obvious as its name, this language is an extension of the C language.

It allows programmers to have high control over system resources and memory. You might think it’s already updated. However, the language has been updated three times in 2011, 2014, and 2017. It went from C++11, C++14, to C++17.

Until today, the C++ language is very well appreciated due to its significant portability, allowing creators to develop programs that can efficiently run on different operating systems or platforms.

Why Do Many Uses C++?

This language is prevalent because it’s an object-oriented programming language that provides a clear structure to programs and helps lower development costs by allowing code to be reused.

Due to its high performance, this language is used to develop games, desktop apps, browsers, and operating systems. Another feature of this language is that it’s portable and allows one to create applications that they can adapt to multiple platforms.

Although it’s known to be one of the most challenging languages to learn, it has its advantages. It’s more challenging to understand than others due to its multi-paradigm language and its functions more advanced syntax.

If you’re able to learn the C++ language, it becomes mucher to learn other programming languages after this one, such as Java and Python.

In short, C++ is a general-purpose, is middle-level programming language that makes it possible to code it in a “C style.” In some cases, you can perform coding in either format, making C++ an example of a hybrid language.

Close-up of Coding/Programming language in a monitor.
The C and C++ languages have a Null character, a Null pointer, and a Null statement (represented by a semicolon (;)).

What’s a Null in C++?

Null is considered a built-in constant that holds the value of zero. It’s both a constant and a pointer in computer programming.

While in a database, zero is a value. The value Null indicates that no value exists. When Null is used as a value, it’s not a memory location.

Moreover, without a Null character, a string wouldn’t be able to terminate appropriately, leading to many problems. The Null character has many different usages across different programming languages.

The question is how you would write the Null in C++. Well, if a Null constant has an integer type, it can then be converted to a value of a sort.

For instance, this character, “Null,” is used in the Structured Query Language (SQL) as a particular marker to indicate that a data value doesn’t exist in the database. A relational database is when a value in a specific column is unknown or missing.

Moreover, in C#, a programming language, Null stands for “no object.” In this language, it’s not the same as the constant zero.

However in C++ language, the Null character is a unique reserved pointer value that doesn’t point to any valid data object. Also, in C++ language, Null functions are just a way to assign value to pointer variables.

Differentiating Between Null and Zero

As Null holds the value Zero, people often get confused over how one would differentiate between Null and Zero.

Null in C++ is just a macro that defines a Null pointer constant and is generally of the value zero. However, Null gives you a significant value representing that the variable doesn’t hold any weight.

Whereas, Zero is a value itself, and that is how it would stay throughout the flow sequence. In other words, Zero is the number value itself, while Null means empty.

You can think of it as a certain space dedicated for a refrigeretor. If the fridge is there but it doesn’t contain anything then the value is Zero. On the other hand, if the space dedicated for the fridge has no fridge at all, the value is Null.

What’s Does Nullptr Mean in C++?

The “Nullptr” keyword represents a Null pointer value. You would use a Null pointer value to indicate that an object handle, interior pointer, or a native pointer type doesn’t point to an object.

Latop and a phone on the table.
Only pointers can hold memory locations, and values can’t.

Firstly, we need to understand what a pointer is. It’s a variable that holds a memory location.

A Null pointer is a pointer that intentionally signals to nothing. If you don’t have an address that you could assign to a pointer, you can use Null. The Null value avoids memory leaks and crashes in applications that have pointers.

Moreover, to check for Nullptr, you could use a pointer value as a condition to check if a pointer is Null in C++. When used in logical expressions, Null pointers are evaluated as false.

Therefore, one can place a given pointer in the if statement condition to check if it’s Null. In short, Nullptr is a pointer-type keyword that represents Zero as an address.

A common question is why the Nullptr is needed when there’s already a Null character. That is because, in C++11, Nullptr is a Null pointer constant, and it’s required because it improves type safety.

Are Null and Nullptr The Same?

No. They’re not. Check out this table below to know first their differences.

NullptrNull
Keyword representing ZeroValue of Zero
Represents Zero as an addressRepresents value as an integer
Newer and suggested functionOlder and deprecated function
True pointer typeImplemented as an alias for integer
constant zero
Take note of the keywords so that you won’t be confused.

Null is considered a “manifest constant” that’s actually an integer and can be assigned to a pointer due to an implicit conversion.

Whereas a Nullptr is a keyword that represents a value of self-defined type, and it can convert into a pointer but not into integers. Nullptr is generally a Null pointer and will always be one. If you try assigning it to an integer, it’ll cause errors.

If you still don’t get that, watch this video.

This video explains thoroughly what and when you should use Null or nullptr—code along with the streamer.

Can You Use Nullptr Instead of Null?

Yes. While they aren’t the same, there’s a way for you to use Nullptr instead of Null.

Besides, Nullptr is a new keyword in C++ that can be of replacement for Null. Nullptr gives a safe type pointer value that represents an empty pointer.

While some avoid using Null because it’s unsuitable, that’s less common nowadays because many coders are following the suggestion to use Nullptr instead of Null.

In addition, you can use the Nullptr keyword to test whether a pointer or handle reference is Null before the reference is used.

Can You Dereference a Nullptr?

You can deference a nullptr. If you do so, you can access the value at the address the pointer is pointing to.

In computer languages, dereferencing is used to access or manipulate data contained in the memory location pointed to by a pointer.

However, you cannot do this in C language. A Null pointer doesn’t point to a meaningful object, an attempt to dereference, which is accessing data stored. A Null pointer usually leads to a run-time error or immediate program crash. 

In computer programming, a dereference operator is what operates on a pointer variable. It returns the location value in memory pointed to by the variable’s value. In C++ programming language, the deference operated is symbolized with an asterisk (*).

Final Thoughts

One can define a Null as a macro that yields to a zero pointer, which means there’s no address for that variable. Null is an old macro in C language passed down to C++.

Meanwhile, Nullptr is a newer version introduced in C++11 and is meant as a replacement for Null.

Therefore, today, it’s recommended that you start using Nullptr in places where you would use Null instead in the past or even as of this writing.

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