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File

The last chapter explained the standard input and output devices handled by C
programming language. This chapter covers how C programmers can create, open, close text or
binary files for their data storage.
A file represents a sequence of bytes, regardless of it being a text file or a binary file. C
programming language provides access on high-level functions as well as low-level (OS level)
calls to handle file on your storage devices. This chapter will take you through the important calls
for file management.

Opening Files
You can use the fopen( ) function to create a new file or to open an existing file. This call
will initialize an object of the type FILE, which contains all the information necessary to control
the stream. The prototype of this function call is as follows:
Here, filename is a string literal, which you will use to name your file, and access mode
can have one of the following values:

FILE *fopen( const char * filename, const char * mode );

Mode Description

r Opens an existing text file for reading purpose.

w Opens a text file for writing. If it does not exist, then a new file is created.
Here your program will start writing content from the beginning of the file.

a Opens a text file for writing in appending mode. If it does not exist, then a
new file is created. Here your program will start appending content in the existing
file content.

r+ Opens a text file for both reading and writing.

w+ Opens a text file for both reading and writing. It first truncates the file to
zero length if it exists, otherwise creates a file if it does not exist.

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