What is Type Checking?

Type Checking is a process that establishes whether a program operation is compliant with the type declaration rules of the programming language. 

In most cases, type checking is done by a compiler. This compiler is able to check and verify whether all operations hold the pre-defined number of arguments and data types.

Type checking is categorized into two systems: static and dynamic.

Static Type Checking

Static type checking offers reliability, security, and saving time since it removes the need to run your program when type checking.

The main advantage of this category includes preliminary error detection. This means that you don’t have to run your program in order to detect said errors. Everything is done beforehand.

A compiler starts the type checking process which is done at compile time. 

Let’s take the C programming language as an example. In this case, you can run your program without declaring the variables within it. However, since you don’t have to declare the variables, the compiler won’t be able to complete its process and will display an error message. In turn, your program will remain static.

Dynamic Type Checking

Dynamic type checking only starts at either runtime or execution time. Therefore, it’s different from the static type checking which occurs at compile time. 

You can write programs without having to worry about having any crucial knowledge about types.

Let's have a look at one of the forms of type checking process:

• Each variable, parameter, and function is assigned a data type;
• Data types determine what kind of operations can be executed;
• Type checking whether the operations are correct.

Unlike the static type checking, where type checking is always performed by the compiler, the dynamic type checking process varies by the programming language. For instance, PHP programming language doesn’t require a compiler while C programming language does.

Additionally, there are such programming languages where programmers are given the ability to take values at run time and associate them with arbitrary properties. Or, if the programming language allows, programmers can define new types to be used within their program algorithms.