Infinite or infinite not

Computer Science Level 3

This is a snippet of code construct in java which gives a simple output :----- 

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byte k=1;
for(  ; k>0 ; k++){

 }
System.out.println(k);

The answer to the question is the value printed i.e. the final value of 'k'. Note : Its a good question so please do not spoil its fun by using a computer to solve it.Have fun...


The answer is -128.

Kartikay Shandil by Kartikay Shandil , 25, India

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1 solution

Kartikay Shandil
Jun 27, 2014

When the loop value increases then it continues till the value of k reaches maximum a byte can contain i.e. k=127. That all bits are one but the sign bit is zero.
Sign bit zero represents "+" i.e. +ve integer. Sign bit one represents "-" i.e. -ve integer. Now when we call the "k++" and as all the bits are "1" except the sign bit the k++ changes it also to one and thus a -ve number i.e. -128 is generated . This acts as the exit condition for the loop and after that "-128" is printed.

17 Helpful 0 Interesting 0 Brilliant 0 Confused

good explaination..!! (Y)

Harshvardhan Mehta - 6 years, 11 months ago

could not understand anything. can you explain that from the point of view of a non programmer, please?

Andrea Toffanin - 6 years, 11 months ago

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In a computer the data is stored in form of binary digits i.e. 0 & 1 The different datatypes in java represent different storing capacities of a number here byte ...... Its Capacity is -128 to 127. When max value is reached then all bits are one then when the k++ statement is called then the - , + bit is also increased from 0 to one (0 representing + and 1 -) so we get the -ve number -128 to understand more read binary representation of a number

Kartikay Shandil - 6 years, 11 months ago

Good explanation. However, a signed byte can only store positive values till 127 (-(2^7) to 2^7-1) not 128. Therefore,k=127 is the largest value after which it wraps to -128(which is less than 0)

PradyGame Dev - 6 years, 8 months ago

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Thanks I have done the needful

Kartikay Shandil - 6 years, 8 months ago

thought that it would be 127

Aishwary Omkar - 6 years, 7 months ago

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