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- Steve Jobs

C Files

A file is a collection of related records stored in a secondary storage of the computer. These informations are stored permanently. C allows programmers to read and write to the files when required.

C Files

File Types in C

  • Text Files
  • Binary Files

C Text Files

A text file consisting of sequence of characters, numbers or contain sequence of lines. C provides library functions to access text files.

Binary Files

A Binary file consisting of collection of bytes.

Reading And Writing Into a File

Step 1: Before starts reading or writing into a file, programmers should declare a file pointer variable which points to a structure FILE. This helps to access file.

Syntax - File pointer declaration

Syntax
FILE *fptr;

The above syntax represent the FILE structure has the pointer variable *fptr. The file pointer is used to access the file.

Step 2: A file must be opened before the reading and writing operation begins. The function fopen() is the only function used to open a file.

C Opening Modes of Files

Mode Meaning Description
w Write Create a file for writing, if the file already exist, it will be used to overwrite a file.
r Read Opening a file for reading only
a Append Opening a file to writing at an end of file.
w+ Write + Read Opening a file for writing and reading
r+ Read + Write Opening a file for reading and writing
a+ Append + Read Opening a file to update or append information

Syntax - Open a File

Syntax
FILE *fptr ;
fptr = fopen("data.dat", "r");

The above syntax represents that the fopen() function will open the file data.dat in read mode. The function fopen checks the disk for a file(data.dat), if the file already exists, it will be opened for further read or write operation. Otherwise, it creates a new file.

Step 3: After completion of reading and writing operations, the file must be closed. C provides a special function fclose() to closing a file.

Syntax - Closing a File

Syntax
fclose(fptr);

C program - Files

files.c
#include <stdio.h>
int main()
{
FILE *fptr;
fptr = fopen("data.dat","r");
if(fptr == NULL)
printf("ERROR: Not able to open the file ");
else
fclose(fptr);
return 0;
}
  • ERROR: Not able to open the file

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