Why we put ifdef and define in Header File in C++

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why we put those lines when we are going to make a header file in C++ ?

#ifndef TIME1_H
#define TIME1_H

Posted 1-Nov-12 8:08am

missak boyajian

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CPallini · Accepted Answer · 2012-11-01T08:42:00

Solution 2

It is an include guard (see Wikipedia[^]), protects against the multiple inclusions of the same header.
The Microsoft compiler (and some others as well) provides the #pragma once directive for addressing the same problem.

Posted 1-Nov-12 8:42am

CPallini

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fjdiewornncalwe 1-Nov-12 16:59pm

+5.

fjdiewornncalwe · Accepted Answer · 2012-11-01T08:11:00

Solution 1

It is a preprocessor designed to avoid the redeclaration of a specific item. In this case, if TIME_H was defined in a previously loaded header, then the compiler would throw a compilation error on a redefinition. The #ifndef simply means "If this isn't defined yet" then #define TIME1_H

Posted 1-Nov-12 8:11am

fjdiewornncalwe