File Opening Modes in C++ programming with descriptions are listed below. You can see in the following table, these modes are used to read/write and work with Files.
| Mode | Use |
|---|---|
| "r" | Searches file. If the file is opened successfully fopen( ) loads it into memory and
sets up a pointer which points to the first character in it. If the file cannot be
opened fopen( ) returns NULL. Operations possible – reading from the file. |
| "w" | Searches file. If the file exists, its contents are overwritten. If the file doesn't
exist, a new file is created. Returns NULL, if unable to open file. Operations possible – writing to the file. |
| "a" | Searches file. If the file is opened successfully fopen( ) loads it into memory and
sets up a pointer that points to the last character in it. If the file doesn't
exist, a new file is created. Returns NULL, if unable to open file. Operations possible - adding new contents at the end of file. |
| "r+" | Searches file. If is opened successfully fopen( ) loads it into memory and sets up a
pointer which points to the first character in it. Returns NULL, if unable to open
the file. Operations possible - reading existing contents, writing new contents, modifying existing contents of the file. |
| "w+" | Searches file. If the file exists, its contents are overwritten. If the file doesn't
exist a new file is created. Returns NULL, if unable to open file. Operations possible - writing new contents, reading them back and modifying existing contents of the file. |
| "a+" | Searches file. If the file is opened successfully fopen( ) loads it into memory and
sets up a pointer which points to the first character in it. If the file doesn't
exist, a new file is created. Returns NULL, if unable to open file. Operations possible - reading existing contents, appending new contents to end of file. Cannot modify existing contents. |