Solidity Data Types – An Ultimate Guide


Solidity is the most popular language in the domain of decentralized applications right now. It is the preferred choice for developing smart contracts and has been developed by the Ethereum Network for this purpose. The interest in learning about Solidity data types has increased profoundly in recent times. What could be the possible reasons? Solidity is a high-level, object-oriented programming language for developing smart contracts and decentralized applications.

Most important of all, it offers useful support for libraries, inheritance, and advanced user-defined data types. As a statically typed programming language, Solidity requires a specification for each variable at the time of compilation. Now, the data types in Solidity for variables would be the ones created by the developer, which don’t offer facility for dynamic changes. The following discussion offers a detailed overview of all the data types you can find in Solidity programming language.

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Data Types in Solidity

The design of Solidity programming language draws inspiration from other notable high-level languages such as C++ and JavaScript. Therefore, the answers to “What are the Solidity data types in blockchain?” might not be as difficult as you imagine. You can find many similarities between data types on Solidity and other popular object-oriented programming languages. On the other hand, Solidity also presents subtle differences from the programming languages in terms of data types. 

Even if Solidity classifies data into multiple types, it is quite unique. How? Solidity facilitates the flexibility for combining different elementary data types to develop complex data types. You can find two distinct Solidity types with value types and reference types, which are integral requirements for developing smart contracts. Let us learn more about the data types in each category. 

Value Types

Value types in Solidity are one of the significant examples of how functional Solidity data structures work and their importance. Value type works by storing data directly in the memory under its ownership. Different variables associated with value types provide flexibility for duplication with their appearance in assignments or functions. 

It is also important to note that a value type could maintain an independent copy of duplicated variables. In such cases, you must note that modifications in value of a duplicated variable cannot affect the value of an original variable. The notable examples of value types in Solidity include signed integers, unsigned integers, addresses, bytes, enums, and Boolean. Here is a description of each value type in Solidity programming language. 

The Boolean or “bool” value data type is one of the important Solidity data types for cases where you find binary results. Boolean data type has two fixed values, such as true or false, and the false value is the default. Boolean data types consume only around 1 byte of storage. You can find support for all standard Boolean operators on Solidity. 

Some of the common examples include inequality (!=), equality (==), and logical negation (!). You can also find other logical Boolean operators such as logical disjunction (&&) and logical conjunction (||). It is also important to remember that Solidity does not support translation of Boolean data types into integers. In addition, assignments to other Boolean variables result in creation of a new copy of the variable.

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The examples of Solidity data structures in value types would also draw attention towards Enums or enumeration. Enums are basically the values in Solidity, which include user-defined data types. The Enum data type applies specifically to constant values like the names of integral constants. They can help in improving the ease of reading and maintaining a smart contract. Furthermore, the Enums data type also provides better ease for reducing the occurrence of bugs in your desired code. 

Enums can help in restricting a variable to a few specific predefined values alongside each copy, maintaining its desired value. The options in the case of Enums find representation with integer values starting from zero and the flexibility for specifying a default value for enum. However, the most striking fact about Enum data types in Solidity is that decentralized applications do not recognize it within smart contracts. It is important to provide an integer value corresponding to the enum constant.     

The overview of answers to “What are the Solidity data types in blockchain?” would also shed light on signed integers. Signed integer data types are generally declared by using the “int” keyword. A signed integer is basically a value data type for storing positive or negative values in smart contracts. 

The “int” keyword is actually an abbreviation of the int256, which comes with a range spanning from -2**255 to 2**255 – 1. The signed integer data type can take almost 32 bytes of storage by default. On the other hand, users can also reduce the storage space for signed integer data types through specification of the number of bits in steps of 8, such as int8, int32, int64, and so on. 

The next entry among value types in discussions on Solidity types would refer to unsigned integers. You can declare an unsigned integer by using the ‘uint’ keyword. An unsigned integer is a value type among data types on Solidity, which should always maintain a non-negative value. Therefore, the value of unsigned integer data types is always equal to or greater than zero. The “uint” keyword serves as an abbreviation for uint256, and the unsigned integer data type consumes around 32 bytes as the default value. 

You can reduce the storage space for unsigned integers through specification of the number of bits in multiples of 8, such as uint8, uint32, uint64, and so on. In addition, unsigned integers are limited to a specific range according to their size. For example, uint32 would have a range from 0 to 2 ** 32 -1 while uint64 would have a range from 0 to 2 ** 64 -1.

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The list of value types in Solidity data types also includes the “byte” data type. The data type basically points out to the 8-bit signed integers. It is important to note that almost everything stored in memory is available in the form of binary values such as 1 and 0. As a matter of fact, you can consider the bytes value type as one of the examples of Solidity data structures in the form of a dynamically sized byte array. The Bytes value type can facilitate information storage in binary format with the flexibility for growing or shrinking the length of the dynamic array. 

Solidity serves a wide range of lengths ranging from bytes1 to bytes32, with bytes1 representing one byte and bytes32 representing 32 bytes. It is important to remember the default value for the byte value type, i.e., 0 x 00, which helps in preparing the default value.

The final addition among value types in the data types in Solidity programming language refers to Addresses. The Address value type has been specifically tailored for storage capacity ranging up to 20 bits or 160 bits. You can note that the Addresses value type corresponds to the size of an Ethereum address. 

On top of it, Solidity offers two distinct address value types such as ‘address’ and ‘address payable.’ The only difference between the address value types is the fact that ‘address payable’ can help in sending and transferring Ether. The address data type can help in acquiring details of balance by utilizing the .balance method. You can also use the .transfer method for transferring a balance.

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Reference Type

The second important category of Solidity data types points toward the reference types. Solidity reference types are considerably different from the value types considerably as they don’t facilitate direct storage of values by default. On the other hand, reference types work by storing or referencing the address of the concerned data’s location without sharing the data directly. 

It is important to handle reference data types cautiously, owing to their role in dealing with storage locations. Why? Data location is an important determinant of the amount of gas utilized in a transaction. Therefore, inappropriate data location could impose a negative impact on the performance of smart contract development projects. 

The use of reference types is quite unique among Solidity types as the reference variables direct users toward the location where a value is stored. You should also note that reference types could consume over 32 bits of memory in terms of size. At the same time, two different variables could refer to one storage location with modifications in one variable affecting the other. 

The variables pointing to a particular address can serve productive results in enforcing specific changes for a reference data type. You can find many popular Solidity data structures such as string arrays, fixed-size arrays, mapping, array members, and structs. Let us learn more about the reference types on Solidity in detail.

Arrays are one of the popular examples among answers to “What are the Solidity data types in blockchain?” in the domain of reference types. You can define arrays as a collection of variables associated with similar data types, and each variable maintains a unique index. It is important to note that array size determines whether you have a fixed or dynamic array. 

Most important of all, the array data structures in Solidity programming depend on other data types. Arrays store data of different types and facilitate simplification of different processes. For example, the Arrays Solidity data structures can ensure simpler processes for repetition, storing, and searching variables or subsets of variables in a specific group. The unique index location could help in retrieving a specifically requested variable. 

Fixed-size array reference types are associated with a predefined size upon their declaration. You must remember that the ‘new’ keyword is not applicable for fixed-size arrays as the data variables should be initialized inline. The dynamic-size arrays do not feature a predefined size upon declaration. On the contrary, the size of dynamic-size arrays must be determined at run time. You can use the ‘new’ keyword or initialize the dynamic array inline like a fixed-size array.

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The next entry among Solidity data types in reference types refers to array members. Array members have the most distinct property in terms of their length, which specifies the number of elements in the array. After creation, storage arrays feature a specific length. On the other hand, the arrays could have dynamic storage arrays, which would have their length subjected to influence of runtime parameters. 

You can set the length of the dynamically sized arrays strategically to facilitate size adjustments. The two distinct types of operations with array members reference types point at push and pop tasks. The push operations involve a member of a dynamic storage array adding an element to the last position of the array. On the other hand, pop operations remove elements from the last position on a dynamic array, with an exception for string arrays. 

Byte arrays are another popular example among data types in Solidity in the category of reference types. The byte array is basically a dynamic array that could hold a specific number of bytes. However, it is important to difference between bytes value type and the byte arrays. Byte array grabs all the bytes tightly and serves distinct use cases. 

The byte array can help in declaring a state element with the beginning length size or provide a property for measuring read/write length. You can also use the byte array for direct value assignment and push values into the array. In addition, it also helps in dividing the array into code lines for creating fixed-size and dynamic-size arrays. 

The collection of Solidity types also sheds light on string arrays, which are dynamic arrays with unique restrictions. You would not find an index with string arrays, thereby implying the lack of array members. If you want to perform any functions of array members, then you must convert the string variables to bytes. The string arrays generally feature characters enclosed within single or double quotes. 

Mapping is one of the most notable examples of Solidity data structures, and it works just like a dictionary or hashtable in different programming languages. As a matter of fact, mapping is the most commonly used reference type in the Solidity programming language. Mapping keys serve a unique functionality with data storage in the form of key-value pairs. The mapping function can help in retrieving storage data through the supplied key and is applicable for state elements. 

The final addition among Solidity data types refers to structs, which showcase how Solidity is unique from other programming languages. Struct reference type basically refers to the flexibility for creating your new or custom data type. The ‘struct’ keyword can help you combine multiple variables of value type and reference type in a specifically defined structure. 

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Final Words

The answers to “What are the Solidity data types in blockchain?” deliver a comprehensive impression of data types in two different categories. A solidity programming language supports two distinct types of data types, such as value types and reference types. The popular examples of value data types include Boolean, signed and unsigned integers, and bytes. 

On the other hand, examples of reference types include arrays, mapping, and structs. Each data type has a specific role in the functionality of Solidity for designing, defining, and creating smart contracts. You can capitalize on the best functionalities of Solidity programming with fluent command over data types in the language. Learn more about Solidity and its data types with professional training courses now.

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