Is #define banned in industry standards?

Question

I am a first year computer science student and my professor said #define is banned in the industry standards along with #if, #ifdef, <

Answer 1

Macros can not be "banned". The statement is nonsense. Literally.

For example, section 7.5 Errors of the C Standard requires the use of macros:

1 The header defines several macros, all relating to the reporting of error conditions.

2 The macros are

EDOM
EILSEQ
ERANGE

which expand to integer constant expressions with type int, distinct positive values, and which are suitable for use in #if preprocessing directives; and

errno

which expands to a modifiable lvalue that has type int and thread local storage duration, the value of which is set to a positive error number by several library functions. If a macro definition is suppressed in order to access an actual object, or a program defines an identifier with the name errno, the behavior is undefined.

So, not only are macros a required part of C, in some cases not using them results in undefined behavior.