When the
program is terminated, the entire data is lost in C programming. If you want to
keep large volume of data, it is time consuming to enter the entire data. But,
if file is created, these information can be accessed using few commands.
There are
large numbers of functions to handle file I/O in C language. In this tutorial,
you will learn to handle standard I/O(High level file I/O functions) in C.
High level
file I/O functions can be categorized as:
1.
Text file
2.
Binary file
File Operations
1.
Creating a new file
2.
Opening an existing file
3.
Reading from and writing information to a file
4.
Closing a file
Working with file
While
working with file, you need to declare a pointer of type file. This declaration
is needed for communication between file and program.
FILE *ptr;
Opening a file
Opening
Modes in Standard I/O
|
||
File Mode
|
Meaning
Of Mode
|
During
Inexistence Of File
|
r
|
Open
for reading.
|
If
the file does not exist, fopen() returns NULL.
|
w
|
Open for writing.
|
If the file exists, its contents are overwritten. If the
file does not exist, it will be created.
|
a
|
Open
for append. i.e, Data is added to end of file.
|
If
the file does not exists, it will be created.
|
r+
|
Open for both reading and writing.
|
If the file does not exist, fopen() returns NULL.
|
w+
|
Open
for both reading and writing.
|
If
the file exists, its contents are overwritten. If the file does not
exist, it will be created.
|
a+
|
Open for both reading and appending.
|
If the file does not exists, it will be created.
|
Closing a File
The file
should be closed after reading/writing of a file. Closing a file is performed
using library function fclose().
fclose(ptr); //ptr is the file pointer associated with file to be closed.
The Functions fprintf() and fscanf() functions.
The
functions
fprintf() and fscanf() are the file version of printf() and fscanf(). The
only difference while using fprintf()and fscanf() is that, the first argument is a pointer to the structure FILE.
Other
functions like
fgetchar(), fputc() etc. can be used in similar way.
Binary Files
Depending
upon the way file is opened for processing, a file is classified into text file
and binary file.
If a
large amount of numerical data it to be stored, text mode will be insufficient.
In such case binary file is used.
Working
of binary files is similar to text files with few differences in opening modes,
reading from file and writing to file.
Opening modes of binary files
Opening
modes of binary files are
rb, rb+, wb, wb+,ab and ab+. The
only difference between opening modes of text and binary files is that, b is
appended to indicate that, it is binary file.
Reading and writing of a binary file.
Functions
fread() and fwrite() are used for reading from and writing to a file on the disk
respectively in case of binary files.
Function
fwrite() takes four arguments, address of data to be written in disk, size of
data to be written in disk, number of such type of data and pointer to the file
where you want to write.
fwrite(address_data,size_data,numbers_data,pointer_to_file);
Function
fread() also take 4 arguments similar to fwrite() function as above.
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