Can anyone please tell me how the value of *++ptr becomes 17?

Question

https://code.sololearn.com/cilZImbd3Lmu/?ref=app

Answer 1

May I ask first, what did you think happened in line 6 and 9? what are you incrementing? is it value at address of <var> or some other address in memory?

Different compiler yields different result.

Answer 2

Keerthana.S the value 17 is whatever happens to be in memory two bytes above the storage for main's local variables. You can see this in a more controlled manner if you define two more local char variables above var.

char c = 2;
char b = 1;
char var=20;
char *ptr=&var;
*++ptr=2;

Now ptr will point to c, and it will no longer print 17. It will print whatever value you use to initialize c (in this example: 2).