cppreference.com > Standard C I/O > fopen fopen Syntax:
      #include <stdio.h>
      FILE *fopen( const char *fname, const char *mode );
The fopen() function opens a file indicated by fname and returns a stream associated with that file. If there is an error, fopen() returns NULL. mode is used to determine how the file will be treated (i.e. for input, output, etc)
Mode | Meaning
--- | ---
"r" | Open a text file for reading
"w" | Create a text file for writing
"a" | Append to a text file
"rb" | Open a binary file for reading
"wb" | Create a binary file for writing
"ab" | Append to a binary file
"r+" | Open a text file for read/write
"w+" | Create a text file for read/write
"a+" | Open a text file for read/write
"rb+" | Open a binary file for read/write
"wb+" | Create a binary file for read/write
"ab+" | Open a binary file for read/write
An example:
       char ch;
       FILE *input = fopen( "stuff", "r" );
       ch = getc( input );
Related topics: fclose fflush fgetc fputc fread freopen fseek fwrite getc getchar setbuf