What is a runtime error?

A runtime error refers to an issue that occurs while the program is executing rather than during the compilation phase. When a program encounters a runtime error, it can lead to an abnormal termination, meaning that the program stops running unexpectedly. This type of error can be caused by various factors, such as illegal operations (like division by zero), resource limitations (like running out of memory), or unhandled exceptions.

In the context of the other options, the first choice describes compilation errors, which happen before the program runs and are related to syntax or type issues in the code. The third option addresses logical errors, which occur due to flaws in the program's logic and might not cause the program to terminate but rather yield incorrect results. The fourth choice mentions variable initialization errors, which can also lead to runtime exceptions, but they are more specific and don't encompass the broader category of runtime errors.

Thus, B accurately captures the essence of a runtime error, emphasizing its impact on the execution of a program.