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Negative binary numbers problem

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engr.waqas

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in using 2's complement the -12 in binary is 11110100.
but if i convert 11110100 to decimal using calculator gives me 244.
So if i have the binary number 11110100 then how can i find that is it -12 or 244?
 

the binary number you enter in calculator is taken as
unsigned positive 8bit binary. so it gives its value.

unless your calculator has a mode to enter the 2's complement numbers it will be the result.

for you the binary shown is '2's complement'.

srizbf
27thjune2010
 

it depends upon the instruction that is used for the number.

srizbf
27thjune2010
 

Whenever you are writing software, you are usually in control of how numbers are handled. In C you define a number as unsigned or not. In assembler the micro may have instructions which operate signed or unsigned. You need to make sure you use the correct instructions with the right variables. In other words, if you have defined a variable as signed, you cannot later use instructions meant for unsigned data without first performing some conversion. You also need to be a careful changing the number of a bits. An 8 bit signed number converted to 16 bits needs 1s adding to the upper byte if the 8 bit number was negative.

Keith
 

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    engr.waqas

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Glad to help. See the www link on my profile - that is what I do. It may look like a large company, but it is all me ;)

Keith
 

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