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Shift Left and Right Returning wrong Result.

 
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kufre



Joined: 19 Oct 2013
Posts: 7
Location: Nigeria

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Shift Left and Right Returning wrong Result.
PostPosted: Mon Oct 21, 2013 8:57 am     Reply with quote
Hey Guys!

Pls can anyone help me out?

Am performing a bit-wise operation on data but I got a weird result.
Here is the code:
Code:

int8 testBitwise(void)
{
   unsigned int8 msb, lsb;
   unsigned int16 result;
   
   msb = 31;
   lsb = 48;
     
   result= (msb << 4) | (lsb >> 4);
   printf("%Lu", result);
   
}

On running the code, I got the "243" as the result.
But verifying the same values (for msb and lsb) on the windows' calculator (programmer's mode), I got "499" which is correct.

Pls could it be the variable type that is the problem or am using the bit-wise operator wrongly. I've not done this before.

I need your help!
Thanks
newguy



Joined: 24 Jun 2004
Posts: 1909

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PostPosted: Mon Oct 21, 2013 9:02 am     Reply with quote
Code:
int8 testBitwise(void)
{
   unsigned int8 msb, lsb;
   unsigned int16 result;
   
   msb = 31;
   lsb = 48;
     
   result= ((unsigned int16)msb << 4) | ((unsigned int16)lsb >> 4);
   printf("%Lu", result);
   
}


You have to tell the compiler to treat your int8's like int16's.
kufre



Joined: 19 Oct 2013
Posts: 7
Location: Nigeria

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Shift Left and Right Returning wrong Result.
PostPosted: Mon Oct 21, 2013 9:11 am     Reply with quote
Thanks newguy for your help. Its now working as expected.
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