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In the D programming language, data types refer to an extensive system used for declaring variables or functions of different types. The type of a variable determines how much space it occupies in storage and how the stored bit pattern is interpreted.
The types in D can be classified as follows −
| Sr.No. | Types & Description |
|---|---|
| 1 |
Basic Types They are arithmetic types and consist of the three types: (a) integer, (b) floating-point, and (c) character. |
| 2 |
Enumerated types They are again arithmetic types. They are used to define variables that can only be assigned certain discrete integer values throughout the program. |
| 3 |
The type void The type specifier void indicates that no value is available. |
| 4 |
Derived types They include (a) Pointer types, (b) Array types, (c) Structure types, (d) Union types, and (e) Function types. |
The array types and structure types are referred to collectively as the aggregate types. The type of a function specifies the type of the function”s return value. We will see basic types in the following section whereas other types will be covered in the upcoming chapters.
Integer Types
The following table gives lists standard integer types with their storage sizes and value ranges −
| Type | Storage size | Value range |
|---|---|---|
| bool | 1 byte | false or true |
| byte | 1 byte | -128 to 127 |
| ubyte | 1 byte | 0 to 255 |
| int | 4 bytes | -2,147,483,648 to 2,147,483,647 |
| uint | 4 bytes | 0 to 4,294,967,295 |
| short | 2 bytes | -32,768 to 32,767 |
| ushort | 2 bytes | 0 to 65,535 |
| long | 8 bytes | -9223372036854775808 to 9223372036854775807 |
| ulong | 8 bytes | 0 to 18446744073709551615 |
To get the exact size of a type or a variable, you can use the sizeof operator. The expression type.(sizeof) yields the storage size of the object or type in bytes. The following example gets the size of int type on any machine −
import std.stdio;
int main() {
writeln("Length in bytes: ", ulong.sizeof);
return 0;
}
When you compile and execute the above program, it produces the following result −
Length in bytes: 8
Floating-Point Types
The following table mentions standard float-point types with storage sizes, value ranges, and their purpose −
| Type | Storage size | Value range | Purpose |
|---|---|---|---|
| float | 4 bytes | 1.17549e-38 to 3.40282e+38 | 6 decimal places |
| double | 8 bytes | 2.22507e-308 to 1.79769e+308 | 15 decimal places |
| real | 10 bytes | 3.3621e-4932 to 1.18973e+4932 | either the largest floating point type that the hardware supports, or double; whichever is larger |
| ifloat | 4 bytes | 1.17549e-38i to 3.40282e+38i | imaginary value type of float |
| idouble | 8 bytes | 2.22507e-308i to 1.79769e+308i | imaginary value type of double |
| ireal | 10 bytes | 3.3621e-4932 to 1.18973e+4932 | imaginary value type of real |
| cfloat | 8 bytes | 1.17549e-38+1.17549e-38i to 3.40282e+38+3.40282e+38i | complex number type made of two floats |
| cdouble | 16 bytes | 2.22507e-308+2.22507e-308i to 1.79769e+308+1.79769e+308i | complex number type made of two doubles |
| creal | 20 bytes | 3.3621e-4932+3.3621e-4932i to 1.18973e+4932+1.18973e+4932i | complex number type made of two reals |
The following example prints storage space taken by a float type and its range values −
import std.stdio;
int main() {
writeln("Length in bytes: ", float.sizeof);
return 0;
}
When you compile and execute the above program, it produces the following result on Linux −
Length in bytes: 4
Character Types
The following table lists standard character types with storage sizes and its purpose.
| Type | Storage size | Purpose |
|---|---|---|
| char | 1 byte | UTF-8 code unit |
| wchar | 2 bytes | UTF-16 code unit |
| dchar | 4 bytes | UTF-32 code unit and Unicode code point |
The following example prints storage space taken by a char type.
import std.stdio;
int main() {
writeln("Length in bytes: ", char.sizeof);
return 0;
}
When you compile and execute the above program, it produces the following result −
Length in bytes: 1
The void Type
The void type specifies that no value is available. It is used in two kinds of situations −
| Sr.No. | Types & Description |
|---|---|
| 1 |
Function returns as void There are various functions in D which do not return value or you can say they return void. A function with no return value has the return type as void. For example, void exit (int status); |
| 2 |
Function arguments as void There are various functions in D which do not accept any parameter. A function with no parameter can accept as a void. For example, int rand(void); |
The void type may not be understood to you at this point, so let us proceed and we will cover these concepts in upcoming chapters.
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