fprintf()

fprintf(FILE *stream, const char *StringAndAnyVariableTags);

	char MyString[] = {"world!"};
	if (fprintf(File1, "Hello %s", MyString) < 0)
	{
		//An error occured
	}

	if (fprintf(File1, "%s %s %d", "Hello", "world", 1234) < 0)
	{
		//An error occured
	}

For the tags you can use see here.

fputc

fputs

	fputs("Hello there\r\n", File1);

	char MyString[] = {"world!"};
	fputs(&MyString[0], File1);

fwrite

fflush()

fflush(FILE *stream);

	fflush(File1);