Header file c file handling

For example the Time class member functions would be defined in the file Time. This file should be stored by the name main. The clients of the class know what member functions the class provides, how to call them and what return types to expect.

Using file handling we can store our data in Secondary memory Hard disk. A file must be close after completion of all operation related to file. For closing file we need close function. Both ios :: app and ios :: ate take us to the end of the file when it is opened. The difference between the two parameters is that the ios :: app allows us to add data to the end of file only, while ios :: ate mode permits us to add data or to modify the existing data any where in the file. Each file have two associated pointers known as the file pointers.

One of them is called the input pointer or get pointer and the other is called the output pointer or put pointer. The input pointer is used for reading the contents of a given file location and the output pointer is used for writing to a given file location.

When we want to move file pointer to desired position then use these function for manage the file pointers. The function put write a single character to the associated stream. This technique is used to search for the file s within the directory that contains the current file.

C's include preprocessor directive statement tries to go through the C preprocessors to scan for a specific file, such as input, before following the rest of your existing source file. Let us take an example where you may think of having a header file karl. You can use various header files based on some conditions. In case, when a header file needs to be included twice within your program, your compiler will be going to process the contents inside it - twice which will eventually lead to an error in your program.

So to eliminate this, you have to use conditional preprocessor directives. Here's the syntax:. Again, sometimes it's essential for selecting several diverse header files based on some requirement to be incorporated into your program. For this also multiple conditional preprocessors can be used like this:. JavaScript Tutorials jQuery Tutorials. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services.

Privacy policy. The names of program elements such as variables, functions, classes, and so on must be declared before they can be used. The declaration tells the compiler whether the element is an int , a double , a function , a class or some other thing.

Furthermore, each name must be declared directly or indirectly in every. When you compile a program, each. The compiler has no knowledge of what names are declared in other compilation units.

That means that if you define a class or function or global variable, you must provide a declaration of that thing in each additional. Each declaration of that thing must be exactly identical in all files. A slight inconsistency will cause errors, or unintended behavior, when the linker attempts to merge all the compilation units into a single program.

You make the declarations in a header file, then use the include directive in every.