C Programming - Complicated Declarations - Discussion

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"I never think of the future. It comes soon enough."

- Albert Einstein

What will be the output of the program?

#include<stdio.h>
typedef unsigned long int uli;
typedef uli u;

int main()
{
    uli a;
    u b = -1;
    a = -1;
    printf("%lu, %lu", a, b);
    return 0;
}

[A].	4343445454, 4343445454	[B].	4545455434, 4545455434
[C].	4294967295, 4294967295	[D].	Garbage values

Answer: Option A

Explanation:

The system will treat the negative numbers with 2's complement method.

For 'long int' system will occupy 4 bytes (32 bits).

Therefore,

Binary 1 : 00000000 00000000 00000000 00000001

To represent -1, system uses the 2's complement value of 1. Add 1 to the 1's complement result to obtain 2's complement of 1.

So, First take 1's complement of binary 1 (change all 0s to 1s and all 1s to 0s)

1's complement of Binary 1:

11111111 11111111 11111111 11111110

2's complement of Binary 1: (Add 1 with the above result)

11111111 11111111 11111111 11111111

In HexaDecimal

11111111 11111111 11111111 11111111 = FFFF FFFF FFFF FFFF

In Unsigned Integer

11111111 11111111 11111111 11111111 = 4294967295.

Nandu said: (Tue, Dec 27, 2011 08:40:12 PM)

Unsigned integer means I mean how we can change ffff ffff ffff ffff to 4294967295. Please anyone explain.

Vanita said: (Thu, Feb 9, 2012 02:52:27 PM)

Quite confusing can any one explain it properly?

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C Programming - Complicated Declarations - Discussion

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