pointers basic question

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C++

char * p = "hello";
cout<<p; 
cout<<p+1;
cout<<*p;

output

hello
105
h

Can any one explain the first two outputs please?

Posted 9-Sep-11 9:34am

robin700

Updated 9-Sep-11 9:43am

Wendelius

v2

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Comments

Philippe Mori 9-Sep-11 18:27pm

Are you sure that your second line is 105? If so, your compiler is broken.

3 solutions

Solution 3

C++

HELLO! this my greeetings!!!

I ran ur code in vc2005. my pc has win 7..

C#

char * p = "hello";
cout<<p;   // printing the char pointer wihtout any condition
cout<<p+1; // printing the pointer skipping the first character
cout<<*p;// printing the value at the address char p[0]. which is p[0].

I got the following anwser which is as expected:

hello
ello
h

please re-build the project and try again!

Posted 11-Sep-11 21:40pm

Arun Parthasarathy

Solution 1

1) p is a pointer to a character array and giving it to cout will print the contents as a string
2) p+1 is evaluated as a contents of the first char in the array + 1 ie h=104 + 1
3) *p means the contents of the address the pointer is pointing to which is a character which is h

Posted 9-Sep-11 10:03am

Mehdi Gholam

Comments

Simon Bang Terkildsen 9-Sep-11 16:07pm

about 2) that must depend on your compiler, as I would expect it to print "ello" and I've just tried it with VC++ and I get "ello". cout<<*p+1; prints 105

Philippe Mori 9-Sep-11 18:26pm

Effectivelly, it should print "ello". Thus answer #2 is not valid.

Sergey Alexandrovich Kryukov 10-Sep-11 0:10am

Ha-ha...
--SA

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Emilio Garavaglia · Accepted Answer · 2011-09-09T10:55:00

Something strange, here:
according to the standard, your compiler and or the standard library aren't standard, or ... you did a typo.

The key is the << operator between cout and the expressions.
p is a char*, and << sends out the sequence of character it points to up to the '\0' implicitly appended to the definition of the "hello" literal (hence, it prints hello).
p+1 is a char* pointing to the next of "h", and works the same as before (hence , should had been printing ello.
*p is a character, and << just prints it.
*p+1 is an expression that evaluates to an integer: *p is the char 'h', and + between a char and an int promotes the char as int and adds the integers. 'h' is 104, adding 1 gives 105 (and it's printed).