endian closed

Question

int main()
{
   int a = 300;    
   char *b = (char *)&a;
   *++b = 2;
   printf("%d ",a);
   return 0;
}

Consider the size of int as two bytes and size of char as one byte.Machine is little-endian

O/P_________

a=300-->(00000001  00101100)₂

now b will point to 00101100

 *++b = 2; what will this do ?

Comments

This question was already asked in gate overflow:

https://gateoverflow.in/147668/programming-and-ds

https://gateoverflow.in/154062/c-programming

Answer 1

300 = 00000001 00101100

endian machine reads in backward direction.

hence b -> 00101100

*++b will be = incrementation of b and then pointing to that value and change that value to 2.

that means after incrementing pointer b by 1, it will point to next 8 bits (i.e. b will point to 00000001)

and *(++b) = 2 will change that value to 2 (i.e. changed value is 00000010)

and hence final value of a = 00000010 00101100

Its decimal equivalent is (2² + 2³ + 2⁵ + 2⁹) = 556.

Hence ans is 556

Comments

Thank You once again :)

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You're welcome! You've great collection of these type of problems! :)

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haha No I was going through random problems over internet for practice .. :)

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endian machine reads in backward direction.

this is true only for little endian m/c as it stores lower byte at lower address and higher byte at higher address unlike in big endian