What are Files in C++
Combination of characters, words, sentences and paragraphs
is called file.
Types of File
Primarily there are two types of files i.e text file(consist
of readable English characters) and executable file.
Text file further categorized into plain text file and
formatted text file.
Properties of file
File properties are file name, file size, file creation date, file modification date etc.
We use files and database for permanent storage because
program run on RAM which is erased once computer is restarted.
Text file handling
C++ filestream is used to handle text file and for this header
file "fstream.h" for C and "fstream" for C++ is used. As cout is used to display program data on screen and
cin is used by program to get data from keyboard.
Similarly header file fstream provides two tool ifstream and
ofstream.
Ifstream is used by program to read data from a file and
ofstream is used by program to write data in file.
Output file handling using ofstream
There are five steps to create text file and write data in
it. These steps are:-
Step 1: Include header file fstream
We have already know how to include built in header files in
our program as to use cout and cin, we included header file iostream at top of
program. Include fstream header file as below.
Step 2: Create object of output file stream
Below line is used to create object of ofstream (output file
stream)
Here ofile is an object of ofstream and we can use this
object to perform all file operations.
Step 3: Create text file and open it
Using dot operator (.), we can call open() method associated
with object ofile. This method will open a new text file if text file of this
name is already not exist. However, if such file already exists, then this
method will only open it to write purpose. Below line is used to do this.
First parameter of open method is text file name. You may
provide complete address of location where you want to create it. If no
location address is mentioned, then file will be created at the location same
as the program.
Second parameter is file opening mode. It means that for
what purpose you are opening the file. We have several options as
- We can create new file, open it and write in it
- We can open already created file, open it and read data from it
- We can open already available file and write in it
- We can delete old date from file and write in it
- We can append data with old data in file
- We can open file and write anywhere in the file
So while opening file, we have to mention that for which
purpose we are opening file like open(filename, mode); mode is option. Default mode
for output file is ios::out
Syntax of different file opening modes are
- ios::in To read data from file
- ios::out Erase old data and write in file
- ios::trunc Erase old date and write in file
- ios::app To append data with old data
- ios::ate Write data anywhere in file
Step 4: Write data in file
Below code will write data which is "usa" in the
file.
Step 5: Close the file
Don’t forget to close file at the end of program so that
resources allocated to ofstream can be de-allocated by the operating system.
Below is a C++ program in which a text file is created, opened and write data in it.
C++ ofstream |
C++ ofstream output |
C++ ofstream myfile.txt |
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