A file is a place where data is stored or retrieved.
It is present in a secondary storage device like Hard Disk Drive (HDD).
In this topic we are going to learn how to store data into the file or retrieve data from the file using I/O (Input/Output) functions like fgetc(), fputc(), fscanf(), fprintf(), fread(), etc.
There are two types of files where data is stored or retrieved.
1) Binary Files
2) Text Files
In Binary Files, data is stored or retrieved in binary form.
In Text Files, data is stored or retrieved in text form.
A File is opened with the help of library function fopen() provided by C.
FILE *fopen(const char *file_name, const char *mode);
This function returns the FILE pointer.
The FILE is a structure provided by C.
FILE *ptr = fopen(const char *file_name, const char *mode);
If there is an error while opening a file, then a NULL value is returned by fopen() function.
FILE *ptr = fopen(“D:\\File\\demo.txt”,”w”);
Above line makes a connection with the file demo.txt present in a folder named FILE inside D drive.
The first argument in fopen() is a path of the file where as second argument is known as a mode.
While opening the file, we need to use the mode.
The mode decides the type of the file operation.
The file is closed using a function fclose() provided by C.
int fclose(FILE *fp);
If there is an error while closing the file, fclose() function returns EOF (End of File with -1) & returns zero on success.
Types of Mode