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A C/C++ Pointer Puzzle
• Difficulty Level : Easy
• Last Updated : 17 Jul, 2017

Prerequisite: Pointers
Assuming the size of int = 4 bytes, size of a pointer variable = 8 byte, what will be the output of following program.
Few hints on how to solve it:

• Size of int = 4 bytes, size of a pointer variable = 8 bytes (on my machine), adding 1 to a pointer makes the pointer point to its next immediate type
• a is of type int (*)
• a1 is of type int *, a2 is of type int **, a3 is of type int **
• &a1 is of type int **, &a2 is of type int ***, &a3 is of type int ****. Since all are pointing to a pointer, therefore adding 1 means adding 8 bytes(sizeof a pointer)
• a is of type int, &a is of type int *, a is of type int *, &a is of type int (*), a is of type int (*), &a is of type int (*), a is of type int (*), &a is of type int (*)
 `// CPP program to illustrate concept``// of pointers``#include ``int` `main()``{``    ``int` `a;``    ``int` `x = 0;``    ``int``* a1 = &x;``    ``int``** a2 = &a1;``    ``int``*** a3 = &a2;``    ``printf``(``"%d %d %d %d\n"``, ``sizeof``(a), ``sizeof``(a1), ``sizeof``(a2), ``sizeof``(a3));`` ` `    ``printf``(``"%d "``, (``char``*)(&a1 + 1) - (``char``*)&a1);``    ``printf``(``"%d "``, (``char``*)(&a2 + 1) - (``char``*)&a2);``    ``printf``(``"%d "``, (``char``*)(&a3 + 1) - (``char``*)&a3);``    ``printf``(``"%d \n"``, (``char``*)(&a + 1) - (``char``*)&a);`` ` `    ``printf``(``"%d "``, (``char``*)(a1 + 1) - (``char``*)a1);``    ``printf``(``"%d "``, (``char``*)(a2 + 1) - (``char``*)a2);``    ``printf``(``"%d "``, (``char``*)(a3 + 1) - (``char``*)a3);``    ``printf``(``"%d \n"``, (``char``*)(a + 1) - (``char``*)a);`` ` `    ``printf``(``"%d "``, (``char``*)(&a + 1) - (``char``*)&a);``    ``printf``(``"%d "``, (``char``*)(&a + 1) - (``char``*)&a);``    ``printf``(``"%d "``, (``char``*)(&a + 1) - (``char``*)&a);``    ``printf``(``"%d \n"``, (``char``*)(&a + 1) - (``char``*)&a);`` ` `    ``printf``(``"%d "``, (a + 1) - a);``    ``printf``(``"%d "``, (``char``*)(a + 1) - (``char``*)a);``    ``printf``(``"%d "``, (``char``*)(a + 1) - (``char``*)a);``    ``printf``(``"%d \n"``, (``char``*)(a + 1) - (``char``*)a);``}`

Output:

```480 8 8 8
8 8 8 480
4 8 8 120
4 24 120 480
1 4 24 120
```

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