File Handling Lecture Slides, Lecture notes of C programming

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File Input/Output

Why files are needed?

• When a program is terminated, the entire data is

lost. Storing in a file will preserve your data even if the program terminates.

• If you have to enter a large number of data, it will

take a lot of time to enter them all. However, if you have a file containing all the data, you can easily access the contents of the file using a few commands in C.

• You can easily move your data from one computer

to another without any changes.

• While working with files, we need to declare a pointer

of type FILE structure. This declaration is needed for communication between the file and the program.

• FILE *fp;
• Opening a file is performed using the fopen() function

defined in the stdio.h header file.

• fp = fopen("fileopen","mode"); - fopen( ) performs three important tasks when you

open the file in “r” mode:

• Firstly it searches on the disk the file to be opened.
• Then it loads the file from the disk into a place in memory called buffer.
• It sets up a character pointer that points to the first character of the buffer.

• When we have finished reading from the file,

we need to close it.

• This is done using the function fclose( )

Counting Characters,

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