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C Language > Learn C Language > How can you avoid including a header more than once?
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How can you avoid including a header more than once?

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Most common ways, use: #pragma once on top of the each header file (though non standard but most compilers support it) or do the following, if you want to protect abc.h from multiple inclusions then in abc.h write following lines: #ifndef _ABC_H_ #define _ABC_H_ ....Contents of your file... #e...
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To avoid multiple inclusions of the same header file we use the #ifndef, #define and #endif preprocessor directives.
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Software Professional Trainer with 26+ years of Experience in Software Design and Development

You can use macro ifndef for example #ifndef TEST_H #define TEST_H ..... other statements here ..... other statements here ..... other statements here #endef
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You can use the conditional preprocessor directive named #ifndef to check whether that symbolic name has already been assigned. If it is assigned, you should not include the header, because it has already been preprocessed. If it is not defined, you should define it to avoid any further inclusions of...
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You can use the conditional preprocessor directive named #ifndef to check whether that symbolic name has already been assigned. If it is assigned, you should not include the header, because it has already been preprocessed. If it is not defined, you should define it to avoid any further inclusions of the header. read less
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Use following in your header file. #ifndef "header_name" #define "header_name" /*header definition starts here*/ #endif /* header file ends here*/ Whenever you will include the same header file, above line wont allow it to get added again. first line of above code checks for header file ,if...
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Use following in your header file. #ifndef "header_name" #define "header_name" /*header definition starts here*/ #endif /* header file ends here*/ Whenever you will include the same header file, above line wont allow it to get added again. first line of above code checks for header file ,if not defined, then the second line starts its definition and 3rd line end the definition. read less
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Programming Trainer

Just write the entire program in only file and include headers once only.
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Thank You for the question Deepak....... You can use conditional pre-processor directive #ifdef or #ifndef. Thank You, Team DishaaPro www.dishaapro.com
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