4.4 File Management in C

Introduction to File Operations in C

• In C programming, files are used to store data permanently on the disk.

• Unlike variables, data in files is not lost when the program ends.

• File operations allow reading, writing, and modifying data stored in files.

         Common file operations:

1. Creating a file
2. Opening a file
3. Reading from a file
4. Writing to a file
5. Closing a file

1) Creating a File: -

• In C, a file is created using the fopen( ) function.

• The fopen( ) function requires two arguments: the file name and the mode.

• To create a new file, we usually use the mode "w" (write) or "a" (append).

• If the file does not exist, "w" will create it. If it exists, "w" will overwrite it.

            Example: -

            Output: - 

2) Opening a File: -

• To access a file, you must first open it using fopen( ).

• Different modes can be used:

                                                                        "r" → read mode

                                                                        "w" → write mode

                                                                        "a" → append mode

                                                                        "r+" → read and write mode

                                                                        "w+" → write and read mode (overwrites file)

• Always check if the file was opened successfully by checking if the pointer is NULL.

             Example: -

             Output: - 

3) Reading from a File: -

• We can read data from a file using functions like fgetc( ), fgets( ), or fscanf( ).

• fgetc( ) reads one character at a time, fgets( ) reads a line, and fscanf( ) reads formatted data.

            Example using fgets( ): -

            Output: - 

4) Writing to a File: -

• We can write data using fputc( ), fputs( ), or fprintf( ).

• fputc( ) writes one character, fputs( ) writes a string, and fprintf( ) writes formatted data.

• Writing to a file in "w" mode overwrites the existing content.

             Example using fputs( ): -

             Output: -

5) Closing a File: -

• After performing file operations, always close the file using fclose( ).

• Closing a file frees up system resources and ensures data is properly saved.

 

            Example: -

            Output: -

Working with text and binary files: -

• In C programming, files are used to store data permanently. Based on how data is stored, files are mainly categorized into text files and binary files.

 

1) Text Files: -

• Text files store data in human-readable format, i.e., as plain characters.

• Each line of a text file ends with a newline character (\n).

• Text files are ideal for small amounts of data that can be read or edited manually.

• Standard functions for text file operations include: fopen( ), fclose( ), fprintf( ), fscanf( ), fgets( ), fputs( ), fgetc( ), and fputc( ).

        Advantages of Text Files

• Human-readable and easy to edit.

• Portable across different platforms.

• Suitable for small data storage.

2) Binary Files: -

• Binary files store data in machine-readable format (binary), not as plain text.

• They are more efficient and faster for large data storage.

• Cannot be read or edited directly with a text editor.

• Functions used: fread( ), fwrite( ), fseek( ), ftell( ), and fclose( ).

                     "wb" → Write in binary mode.

                    "rb" → Read in binary mode.

                    "ab" → Append in binary mode.

 

            Advantages of Binary Files

• Efficient storage, especially for large datasets.

• Faster reading and writing.

• Exact data representation (important for structures, arrays, etc.).

 

Feature	Text File	Binary File
Format	Human-readable	Machine-readable
Size	Larger (due to text)	Smaller
Efficiency	Slower for large data	Faster
Editing	Can be edited manually	Cannot edit manually
Data Loss Risk	Newlines may cause issues	Exact data preserved

            Example: -

            Output: -