How do you create the logical error in c?

Answer 1

It is not clear what do you mean by 'logical error', but perhaps an example will help:

int main (void)

{

FILE *f= fopen ("foobar.txt", "r");

if (f) printf ("couldn't open foobar.txt for reading");

fclose (f);

}

corrected version:

int main (void)

{

FILE *f= fopen ("foobar.txt", "r");

if (f==NULL) {

printf ("couldn't open foobar.txt for reading");

return 0;

}

fclose (f);

}

Logical error can be generated by using the #error directive. This directive doesn't allows the program to run, in certain conditions. An error message has been generated by the compiler because of this preprocessor directive.

e.g.

#define M 10

#if M!=10

#error M must be 10

#endif

in this case no error mesage will be generated because M is equal to 10

#define M 11

#if M!=10

#error M must be 10

#endif

in this case, as M is not equal to 10 error message will be generated by the compiler and the message will be M must be 10.