How will this program get executed?

Question

#include <stdio.h>

void main() { 
    char a = 0xAA;
    int b;
    b = (int) a;
    printf("%d\n", a); 
    b = b >> 4;
    printf("%x", b); 
}

[Question]

I have problem in statement b = (int)a. Can you give the binary representation of b when a is stored in it?

I think you need to know about [`>>` operators](http://stackoverflow.com/questions/17769948/what-does-this-operator-mean-in-c/17769959#17769959) and `a = 0xAA` == `10101010` in binary — Grijesh Chauhan, Aug 25 '13 at 06:17
Why not just [run it yourself and see](http://ideone.com/zaBjWo) ? — Paul R, Aug 25 '13 at 06:19
i have problem in statement b=(int)a. ca you give me the binary form in which it will get stored in b? — user2714916, Aug 25 '13 at 06:23
@user2714916 edit and explain clearly what you wants in question. its typecasting — Grijesh Chauhan, Aug 25 '13 at 06:24
@GrijeshChauhan i have problem in statement b=(int)a. ca you give me the binary form in which it will get stored in b? — user2714916, Aug 25 '13 at 06:33
@user2714916 not `a`'s binary represent is `10101010` in this MSB is set so negative number its value is `-86`. This value remain same in `b` int `-86` because `b` is a int probably in `4` bytes in your system then its should `be = ffffffaa` int binary `1111 1111 1111 1111 1111 1111 1010 1010` — Grijesh Chauhan, Aug 25 '13 at 06:38
@user2714916 Your question is not bad (really good question) but presentation is not good. Please take time to post and ask a question. — Grijesh Chauhan, Aug 25 '13 at 06:40

score 1 · Accepted Answer · answered Aug 25 '13 at 06:31

1

For the statement b = (int)a;, we are typecasting a char to an int. Assuming that char is implicitly signed (NB: not always true!) and that int is 32 bits, then the char value 0xAA gets widened with sign extension, so 0xAA becomes 0xFFFFFFAA which is equivalent to -86 in decimal.

answered Aug 25 '13 at 06:31

Paul R

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@Grijesh: There's no UB in the cast. If you mean here: `b = b >> 4;` then that's *implementation-defined* behaviour, not undefined behaviour. – Paul R Aug 25 '13 at 06:36
@Parul yes I realized so I deleted my comment Thanks. – Grijesh Chauhan Aug 25 '13 at 06:41

Ashwani · Answer 2 · 2013-08-25T06:43:41.960

char a = 0xAA; // line 1
int b; // line 2
b = (int) a; // line 3
printf("%d\n", a); // line 4
b = b >> 4; // line 5
printf("%x", b); // line 6

Line 1: assigned a character to variable a of char type from hexadecimal

Line 2: declaring a variable b of int type

Line 3: Assign value of char a by typecasting to from char to int. It will output a int value.

Line 4: outputs the value of char a in int format

Line 5: reassign value of b by right shifting it to 4.

Line 6: Output value of b in hexadecimal format. So output should be in something e.g.; FFAA454 like.

This is how your code is working.

score 0 · Answer 3 · answered Aug 25 '13 at 06:22

0

If you want to know what the console will output, here is what I get:

-86
fffffffa

In the future if you want to see how a test case is executed try using something like this.

answered Aug 25 '13 at 06:22

Christian Wilkie

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How will this program get executed?

3 Answers3