What is the difference between signed and unsigned variables

Question

I have seen these mentioned in the context of C and C    but what is the difference between signed and unsigned variables

User · Answer

Unsigned variables can only be positive numbers, because they lack the ability to indicate that they are negative.

This ability is called the 'sign' or 'signing bit'.

A side effect is that without a signing bit, they have one more bit that can be used to represent the number, doubling the maximum number it can represent.

User · Answer

Signed variables  such as signed integers will allow you to represent numbers both in the positive and negative ranges  Unsigned variables  such as unsigned integers  will only allow you to represent numbers in the positive and zero  Unsigned and signed variables of the same type  such as int and byte  both have the same range  range of 65 536 and 256 numbers  respectively   but unsigned can represent a larger magnitude number than the corresponding signed variable  For example  an unsigned byte can represent values from 0 to 255  while signed byte can represent -128 to 127  Wikipedia page on Signed number representations explains the difference in the representation at the bit level  and the Integer  computer science  page provides a table of ranges for each signed unsigned integer type

User · Answer

This may not be the exact definition but I ll give you an example   If you were to create a random number taking it from the system time  here using the unsigned variable is beneficial as there is large scope for random numbers as signed numbers give both positive and negative numbers  As the system time can t be negative we use unsigned variable Only positive numbers  and we have more wide range of random numbers

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Unsigned variables are variables which are internally represented without a mathematical sign  plus or minus  can store  zero  or positive values only  Let us say the unsigned variable is n bits in size  then it can represent 2 n  2 power n  values - 0 through  2 n -1   A signed variable on the other hand   loses  one bit for representing the sign  so it can store values from - 2  n-1  -1  through  2  n-1   including zero  Thus  a signed variable can store positive values  negative values and zero    P S   Internally  the mathematical sign may be represented in one s complement form  two s complement form or with a sign bit  eg  0 -     1-  -  All these methods effectively divide the range of representable values in n bits  2 n  into three parts  positive  negative and zero   This is just my two cents worth    I hope this helps

User · Answer

unsigned is used when ur value must be positive  no negative value here  if signed for int range -32768 to  32767 if unsigned for int range 0 to 65535

User · Answer

Signed variables can be 0  positive or negative   Unsigned variables can be 0 or positive   Unsigned variables are used sometimes because more bits can be used to represent the actual value   Giving you a larger range   Also you can ensure that a negative value won t be passed to your function for example

User · Answer

Signed variables use one bit to flag whether they are positive or negative  Unsigned variables don t have this bit  so they can store larger numbers in the same space  but only nonnegative numbers  e g  0 and higher   For more  Unsigned and Signed Integers

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While commonly referred to as a  sign bit   the binary values we usually use do not have a true sign bit   Most computers use two s-complement arithmetic   Negative numbers are created by taking the one s-complement  flip all the bits  and adding one    nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 5  decimal   - gt    00000101  binary   nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 1 s complement    11111010  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp add 1             11111011   which is  FB  in hex   This is why a signed byte holds values from -128 to  127 instead of -127 to  127    nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 1 0 0 0 0 0 0 0   -128  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 1 0 0 0 0 0 0 1   -127  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp - - -  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 1 1 1 1 1 1 1 0   -2  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 1 1 1 1 1 1 1 1   -1  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 0 0 0 0 0 0 0 0   0  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 0 0 0 0 0 0 0 1   1  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 0 0 0 0 0 0 1 0   2  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp - - -  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 0 1 1 1 1 1 1 0   126  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 0 1 1 1 1 1 1 1   127  nbsp  nbsp  nbsp  nbsp  nbsp  nbsp  add 1 to 127 gives    nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 1 0 0 0 0 0 0 0 nbsp  nbsp  nbsp which we see at the top of this chart is -128    If we had a proper sign bit  the value range would be the same  e g   -127 to  127  because one bit is reserved for the sign   If the most-significant-bit is the sign bit  we d have    nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 5  decimal   - gt    00000101  binary   nbsp  nbsp  nbsp  nbsp  nbsp  nbsp -5  decimal   - gt    10000101  binary     The interesting thing in this case is we have both a zero and a negative zero   nbsp  nbsp  nbsp  nbsp  nbsp  nbsp 0  decimal   - gt    00000000  binary   nbsp  nbsp  nbsp  nbsp  nbsp  nbsp -0  decimal   - gt    10000000  binary    We don t have -0 with two s-complement  what would be -0 is -128   or to be more general  one more than the largest positive value    We do with one s complement though  all 1 bits is negative 0   Mathematically  -0 equals 0   I vaguely remember a computer where -0  lt  0  but I can t find any reference to it now

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