Double pointers(pointer to pointer)

Author: georgecatalin

Advanced Pointers/conceptual_example_2_pointer_to_pointer.c

@@ -0,0 +1,34 @@
+#include <stdio.h>
+
+int main(void)
+{
+    int **double_pointer=NULL;
+
+    int var1=10;
+    int var2=43;
+    int var3=64;
+
+    int *pVar1=&var1;
+    int *pVar2=&var2;
+    int *pVar3=&var3;
+
+    double_pointer=&pVar1;
+
+    printf("The memory address where \"double_pointer\" variable is stored is %p.\n",&double_pointer);
+    printf("The value stored in the \"double pointer\" variable %p which is the memory address it points to %p.\n",double_pointer,&pVar1);
+    printf("The value to which the \"double pointer\" points to is %p.\n", *double_pointer );
+    printf("The value derefenced of the \"double pointer\" variable is %d=%d.\n",**double_pointer,*pVar1);
+    puts("--------------------------------");
+    
+    *double_pointer=pVar2; //it means the double_pointer variable is dereferenced as pVar2, so to say the value it points to is pVar2. Hence since double_pointer=&pVar1 it means the pVar1 points to pVar2;
+
+    printf("The value stored in the \"double pointer\" variable %p which is the memory address it points to %p.\n",double_pointer,&pVar1);
+    printf("The value to which the \"double pointer\" points to is %p which is the memory address of where \"pVar2\".\n", *double_pointer );
+    printf("The value derefenced of the \"double pointer\" variable is %d=%d.\n",**double_pointer,*pVar2);
+
+    puts("--------------------- from the points of view of variable \"pVar1\"------------------");
+    printf("The value stored in the variable \"pVar1\" is %p=%p.\n",pVar1,pVar2);
+    printf("The value to which the variable \"pVar1\" points to is %d=%d.\n",*pVar1,*pVar2);
+
+    return 0;
+}

Advanced Pointers/conceptual_example_3_pointer_to_pointer.c

@@ -0,0 +1,28 @@
+#include <stdio.h>
+
+int main(void)
+{
+    int **pointer_to_pointer=NULL;
+
+    int var1=10;
+    int var2=43;
+    int var3=66;
+
+    int *pVar1=&var1;
+    int *pVar2=&var2;
+    int *pVar3=&var3;
+
+    pointer_to_pointer=&pVar1;
+
+    printf("The memory address where the \"pointer_to_pointer\" variable is stored is %p.\n",&pointer_to_pointer);
+    printf("The value of the \"pointer_to_pointer\" variable which is the same value as the memory address where the variable \"pVar1\" is stored is %p=%p.\n",pointer_to_pointer,&pVar1);
+    printf("The dereferenced \"pointer_to_pointer\" variable so to say the value that exists where \"pointer_to_pointer\" variable is pointing to is %p=%p.\n",*pointer_to_pointer,pVar1);
+    printf("The completely derefenced value of the \"pointer_to_pointer\" variable which the value where the intermediate pointer variable points to is %d=%d.\n",**pointer_to_pointer,*pVar1);
+    puts("=============================");
+
+    *pointer_to_pointer=&var3;
+    printf("The memory address where the \"pointer_to_pointer\" variable is stored is %p.\n",&pointer_to_pointer); //these remain the same as above
+    printf("The value of the \"pointer_to_pointer\" variable which is the same value as the memory address where the variable \"pVar1\" is stored is %p=%p.\n",pointer_to_pointer,&pVar1); //these remain the same as above
+    printf("The dereferenced \"pointer_to_pointer\" variable so to say the value that exists where \"pointer_to_pointer\" variable is pointing to is %p=%p.\n",*pointer_to_pointer,pVar1); //due to the change that affects the pointer_to_pointer, the intermediat pointer variable is affected too
+    printf("The completely derefenced value of the \"pointer_to_pointer\" variable which the value where the intermediate pointer variable points to is %d=%d.\n",**pointer_to_pointer,*pVar1);
+}

Advanced Pointers/conceptual_pointer_to_pointer.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+int main(void)
+{
+    int **double_pointer=NULL;
+
+    int var1=10,var2=43,var3=65;
+    
+    int *pVar1=&var1;
+    int *pVar2=&var2;
+    int *pVar3=&var3;
+
+    double_pointer=&pVar1;
+    
+    printf("The value of the double pointer is %p and this is the memory address it points to (=%p) \n", double_pointer,&pVar1);
+    printf("The memory address where is stored the double pointer is %p. \n",&double_pointer);
+    printf("The value stored at the memory address where the double pointer is pointing to is %p while the address the address stored in the intermediate pointer is %p .\n",*double_pointer,pVar1);
+    printf("The final value to where the chain of pointer to pointer is pointing to is %d.\n",**double_pointer);
+
+
+    return 0;
+}

Advanced Pointers/example.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+int main(void)
+{
+    int a=10;
+
+    int *ptr=NULL;
+    int **ptrptr=NULL;
+
+    ptr=&a;
+    ptrptr=&ptr;
+
+    printf("The memory address where the variable \"a\" is stored is %p.\n",&a);
+    printf("The memory address where the variable \"ptr\"i is stored is %p.\n",&ptr);
+    printf("The memory address where the variabe \"ptrptr\" is stored is %p.\n",&ptrptr);
+
+    printf("The value stored at the memory address stored by \"ptr\" is %d.\n",*ptr); //should be a
+    printf("The value stored at the memory address stored by \"ptrptr\" is %p.\n",*ptrptr); //should be &a
+    printf("The value of **\"ptrptr\" is %d.\n ",**ptrptr);
+
+    return 0;
+}