# Conversion issue

Vishy Karl

Ranch Hand

Posts: 116

posted 13 years ago

Hi all,

I am having a doubt in the questions involving hexadecimal numbers.

i had this question in a mock exam

int ab = 0xFFFFFFFA;

int invertedA = ~ab;

Now how am i supposed to find value of ab which is -6,i mean am is supposed to write

A * 16^0 + F * 16^1 + F * 16^2 and so on ???

i don't think this is the proper way,is there no easier way ? how will i get -6 as the answer.

plz. solve my doubt,

thanks in advance.

I am having a doubt in the questions involving hexadecimal numbers.

i had this question in a mock exam

int ab = 0xFFFFFFFA;

int invertedA = ~ab;

Now how am i supposed to find value of ab which is -6,i mean am is supposed to write

A * 16^0 + F * 16^1 + F * 16^2 and so on ???

i don't think this is the proper way,is there no easier way ? how will i get -6 as the answer.

plz. solve my doubt,

thanks in advance.

"The man who can drive himself further once the effort gets painful is the man who will win." <br />Roger Bannister

Steve Lovelace

Ranch Hand

Posts: 125

posted 13 years ago

First, I believe the answer is 5, not -6.

To see how to do the inversion easily, picture what this number looks like in binary. It is:

11111111 11111111 11111111 11111010

Inverting means 1 becomes 0 and vice versa:

00000000 00000000 00000000 00000101

or 101 for short, which is to say 5.

To see how to do the inversion easily, picture what this number looks like in binary. It is:

11111111 11111111 11111111 11111010

Inverting means 1 becomes 0 and vice versa:

00000000 00000000 00000000 00000101

or 101 for short, which is to say 5.

The Inner that is named is not the true Inner.

posted 13 years ago

Don't forget!!! Two's complement means you need to invert the number

So -->

11111111 11111111 11111111 11111010

00000000 00000000 00000000 00000101

+ 1

-----------------------------------

00000000 00000000 00000000 00000110

== 6

So that means it really is -6

But I agree -- the easiest way I've found to convert hex digits is first to convert it to binary then two's complement it (if its negative) and then figure out the decimal representation.

Originally posted by Steve Lovelace:

11111111 11111111 11111111 11111010

Inverting means 1 becomes 0 and vice versa:

00000000 00000000 00000000 00000101

or 101 for short, which is to say 5.

Don't forget!!! Two's complement means you need to invert the number

**and then add 1!**

So -->

11111111 11111111 11111111 11111010

00000000 00000000 00000000 00000101

+ 1

-----------------------------------

00000000 00000000 00000000 00000110

== 6

So that means it really is -6

But I agree -- the easiest way I've found to convert hex digits is first to convert it to binary then two's complement it (if its negative) and then figure out the decimal representation.

Dimple Kaushik

Ranch Hand

Posts: 49

posted 13 years ago

ab=0xFFFFFFFA

in hexadecimal A=10, B=11, C=12, D=13, E=14, F=15

in binary 10,11,12,13,14,15 are 1010, 1011, 1100, 1101, 1110, 1111 resp

so ab = 1111 1111 1111 1111 1111 1111 1111 1010

~ab = 0000 0000 0000 0000 0000 0000 0000 0101 + 1 = 110 = -6

Can anybody tell me how to convert these?

byte a = (byte)127;

byte b = (byte)128;

byte c = (byte)255;

byte d = (byte)256;

//......

System.out.print(a + " " + b + " " + c + " " + d);

Ans: a = 127, b = -128, c = -1, d = 0

Thanks.

[ November 19, 2003: Message edited by: dimple kaushik ]

in hexadecimal A=10, B=11, C=12, D=13, E=14, F=15

in binary 10,11,12,13,14,15 are 1010, 1011, 1100, 1101, 1110, 1111 resp

so ab = 1111 1111 1111 1111 1111 1111 1111 1010

~ab = 0000 0000 0000 0000 0000 0000 0000 0101 + 1 = 110 = -6

Can anybody tell me how to convert these?

byte a = (byte)127;

byte b = (byte)128;

byte c = (byte)255;

byte d = (byte)256;

//......

System.out.print(a + " " + b + " " + c + " " + d);

Ans: a = 127, b = -128, c = -1, d = 0

Thanks.

[ November 19, 2003: Message edited by: dimple kaushik ]

Vishy Karl

Ranch Hand

Posts: 116

posted 13 years ago
"The man who can drive himself further once the effort gets painful is the man who will win." <br />Roger Bannister

Thanks all

Jessica the number given ab is itself -6 according to 2's complement .

then after the operation

int invertedA = ~ab;

it comes to sign change and answer as 5

Thanks all for your answers,

happy preparation,

Jessica the number given ab is itself -6 according to 2's complement .

then after the operation

int invertedA = ~ab;

it comes to sign change and answer as 5

Thanks all for your answers,

happy preparation,