Why header files are used in c

If the header file is defined within the predefined source path, we can specify the header within the angular brackets. If the header file is not defined within the predefined source path then we can specify the full path of the header file within the double-quotes. If the header file in a source code is included twice, then it leads to an error, i. To get rid of this problem, there is a standard way of enclosing the real content of the header file in a conditional as follows:.

In the above condition, if the header is included, then it will not be included again. If the header file is not included, then the header file will be included. The construct "ifndef" will become false if the header file is included twice and the preprocessor will skip all the contents of the file, and the compiler will ignore the second declaration of the header file.

Header file is used to avoid writing large and complex code. When we create our own header file then we can simply use wherever we want.

It enhances code readability and functionality. In the above code, we have observed the usage of header files like string. JavaTpoint offers too many high quality services. Mail us on [email protected] , to get more information about given services. Please mail your requirement at [email protected] Duration: 1 week to 2 week.

Command Line Arguments. Since we have specified the condition in the header file that if the header file is included then the header file should not be included again. When the program control comes to the second statement of include "header. Next Topic abs function in C. Reinforcement Learning. R Programming. Possible Duplicates: [C] Header per source file. Is the only reason header files exist in C is so a developer can quickly see what functions are available, and what arguments they can take?

Or is it something to do with the compiler? Why has no other language used this method? Is it just me, or does it seem that having 2 sets of function definitions will only lead to more maintenance and more room for errors? Or is knowing about header files just something every C developer must know?

Header files are needed to declare functions and variables that are available. The compiler needs the information in the header files to know what functions, structures, etc are available and how to use them. All languages needs this kind of information, although they retrieve the information in different ways. For example, a Java compiler does this by scanning either the class-file or the java source code to retrieve the information.

The drawback with the Java-way is that the compiler potentially needs to hold a much more of information in its memory to be able to do this. This is no big deal today, but in the seventies, when the C language was created, it was simply not possible to keep that much information in memory. To allow the compiler to properly check arguments and return values you either put the function prototype in an header file and include it in the. While you could, in theory, repeat the same declaration in each source file, it would become a real nightmare to properly manage it.

Some language uses the same approach. I remember the TurboPascal units being not very different. You would put use I can't remember if that was passed into Delphi as well. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. What is the point of header files in C? Asked 11 years, 9 months ago. Active 1 year, 10 months ago. Viewed 21k times.

What are variables and it what way is it different from constants? How do you access the values within an array? Can I use "int" data type to store the value ?

Can two or more operators such as and be combined in a single line of program code? Why is it that not all header files are declared in every C program? When is the "void" keyword used in a function?