Add Short Ints: 30064 + 30064 = -60128

[Lightf]

Homework Statement

The question is :

Converting to short int, calculate 30064 + 30064 as short integers.
Convert the answer to decimal ( the answer will be negative ).

Homework Equations

None.

The Attempt at a Solution

I converted 30064 to hex getting 7570.

I then added that to itself getting eae0.

But when i convert that back to dec I just get 60128 ? How am i suppose to get a negative number?

 

[Mark44]

Homework Statement

The question is :

Converting to short int, calculate 30064 + 30064 as short integers.
Convert the answer to decimal ( the answer will be negative ).

Homework Equations

None.

The Attempt at a Solution

I converted 30064 to hex getting 7570.

I then added that to itself getting eae0.

But when i convert that back to dec I just get 60128 ? How am i suppose to get a negative number?

Since you're talking about short integers, I'm assuming you are talking about the short int data type in C or C++. Short ints are 32 bit signed numbers, which means that the largest positive short int is 32,767, or 0x7ffff. Adding 1 to this gives you 0x8000, which is -32,768.

Any short int whose highest order bit is 1 is considered to be negative.

 

[Lightf]

So the answer would be :

7fff - eae0 = 6ae1

6ae1 - 8000 = -151f

which is -5497 in dec.

Is that the correct way of doing it? Thanks for the help.

 

[Filip Larsen]

You may want to look for "two's complement" in your textbook or on the net.

 

[Lightf]

So eae0 is 1110101011100000 but the first 1 just means its a minus number so its -27360