C runtime errors are those errors that occur during the execution of a c program and generally occur due to some illegal operation performed in the program.
Examples of some illegal operations that may produce runtime errors are:
Dividing a number by zero
Trying to open a file which is not created
Lack of free memory space
It should be noted that occurrence of these errors may stop program execution, thus to encounter this, a program should be written such that it is able to handle such unexpected errors and rather than terminating unexpectedly, it should be able to continue operating. This ability of the program is known as robustness and the code used to make a program robust is known as guard code as it guards program from terminating abruptly due to occurrence of execution errors.
