C and C++ are one of the top 3 programming languages worldwide. Type casting is one of the most used methods to convert similar variable types to different types in C and C++. Type casting in C or in C++ can be done by using data type in parenthesis in the code lines in a C++ Editor like C++ Builder or Dev-C++. In this post, we explain type casting in C and other casting methods available to us in C++.
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What is implicit type casting (standard conversion) in C programming?
Implicit type casting is an automatic casting that copies a variable to another compatible variable type, this is also known as a standard conversion. This method does not require any operator, it is automatically performed when a value is copied to a compatible type. Implicit type casting affects fundamental data types and allows conversions such as the conversions between numerical types, to or from bool, and some pointer conversions. For example, we can copy an unsigned char value to an unsigned int value as below,
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#include <stdio.h> int main() { unsigned char c = 221; unsigned int i ; i = c; // Automatic Implicit Type Casting in C / C++ printf("%d", i); getchar(); return 0; } |
Here, the value of i has been promoted from unsigned char to unsigned int and there is no need to specify any type-casting operator. This will output integer value as 221 as same as value of c variable.
Can you show me some wrong examples of type casting in C?
In implicit type casting developer should be careful about variable types. Some of these conversions may imply a loss of precision, which the editor or compiler can signal with a warning. For example, in a char to int conversion, char c will be -35 which comes from 221-256 = -35,
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#include <stdio.h> int main() { char c = 221; int i ; i = c; // Automatic Implicit Type Casting in C / C++ printf("%d", i); getchar(); return 0; } |
Here, the value of i has been promoted from short to int and we have not had to specify any type-casting operator. and the output of the implicit type value of the integer will be -35. Generally, because of these kinds of conversion problems, if you are not sure about types and their ranges, we do not recommend these kinds of type castings. Note that, this warning can be avoided with an explicit conversion.
In another implicit type conversion, higher bit types to lower bit type value conversions may cause a loss of value or wrong values as a result. For example, we have an integer value of 300 and if we convert to char as below
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#include <stdio.h> int main() { int i = 300; char c ; c = i; // Automatic Implicit Type Casting in C / C++ printf("%d", c); getchar(); return 0; } |
This will result the value 44 which comes from 300-256 = 44. If we use the keyword unsigned in front of char then this problem is avoided.
What is explicit type casting in C programming?
C and C++ is powerful decent programming languages. Generally, most of the conversions, especially those that imply a different interpretation of the value, require an explicit conversion.
Here are two different notations,
- Explicit C-Like Type Casting
- Explicit Functional Type Casting
In C-Like explicit type casting, just add type name / data type in parenthesis then expression.
Here is the Syntax of Explicit C-Like Type Casting:
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<new expression> = (data type) <expression> |
In explicit functional casting, just add type name / data type then expression in parenthesis.
Here is the Syntax of Explicit Functional Type Casting:
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<new expression> = data type ( <expression> ) |
Here is a C example to both of these syntaxes:
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#include <stdio.h> int main() { unsigned char c = 221; unsigned int i ; i = (int) c; // Explicit C-Like Casting i = int (c); // Explicit Functional Casting printf("%d", i); getchar(); return 0; } |
In explicit type casting, developer should be careful about variable types too, as given examples above. Some of these conversions may imply a loss of precision without a warning.
What is type casting in C++ programming?
In C++, casting is a technique to convert one data type to another data type. Implicit type casting, explicit C-Like type casting, and explicit functional type casting can be used in C++. In addition to these, there are 4 more casting operators that can be used in casting data types. The operator used for this purpose is known as the cast operator. It is a unary operator which forces one data type to be converted into another data type.
In C++, a cast operator is a Unary Operator which forces one data type to be converted into another data type.
In general, C++ supports four types of casting:
- Static Cast (static_cast)
- Dynamic Cast (dynamic_cast)
- Constant Cast (const_cast)
- Reinterpret Cast (reinterpret_cast)
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There is a free C++ Builder Community Edition for students, beginners, and startups; it can be downloaded from here. For professional developers, there are Professional, Architect, or Enterprise versions of C++ Builder and there is a trial version you can download from here.
