Changes between Version 15 and Version 16 of ResumedC

Timestamp:

May 11, 2009, 5:32:01 PM (16 years ago)

Author:

Thanatermesis

Comment:

--

ResumedC

@@ -249 +249 @@
 }}}
 
-
-
-
+'''Double pointers''': The double pointer can be used for 2 differents things:
+ * A pointer that points to a pointer, so that you can change the value of the original pointer (address value)
+   * ''To modify the value of a variable using pointers in a function, you need to pass the address of that variable'': Same thing when you try to modify the address of a pointer (pointer of a pointer)
+ * A two-dimensional array: like in '''argv''', a matrix, or a list of char*, so (*char[])
+
+{{{
+#!C
+/* Pointer to a pointer */
+void foo( char ** ptr)
+{
+   *ptr = malloc(255);  // allocate some memory, obtain a new address for ptr
+   strcpy( *ptr, "Hello World");  // assign some data to our new addressed pointer
+}
+int main()
+{
+   char *ptr = 0;  // we set a new pointer to null
+   foo( &ptr );  // we call the function with the address (null) of our pointer
+   /* now (after to call the function to assign the pointer), we have 'ptr' with a new address and allocated memory */
+}
+
+int main(int argc, char **argv) /* note that '*argv[]' is equivalent to '**argv'  */
+  /* but since it doesn't means the pointer of a pointer, we should use *argv[] in preference because is more understandable to what really means */
+}}}