operators = and != in the same time

Question

Recently i saw a code that prints number in binary system.
I dont understand line : bit = (dec & 0x8000) != 0;
Is there's anyone that can explan this to me?

int dec,n ;
short bit;


    printf("Insert number: ");
    scanf("%d", &dec);

    if (dec == 9999)  printf(" Out of range!"); 


    for (int i = 1; i <= 16; i++) {
        bit = (dec & 0x8000) != 0;
        printf("%d", bit);
        if (i % 4 == 0) printf(" ");
        dec <<= 1;
    }
    printf("\n");



return 0;

}

Possible duplicate of [What does this ampersand mean in C?](https://stackoverflow.com/questions/24370797/what-does-this-ampersand-mean-in-c) — phuclv, Apr 07 '19 at 15:59

score 3 · Answer 1 · answered Apr 07 '19 at 15:56

3

Assign to the variable bit a value of 1 if the result of evaluating (dec & 0x8000) is not equal to 0; and a value of 0 otherwise.

answered Apr 07 '19 at 15:56

Igor Tandetnik

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score 2 · Answer 2 · answered Apr 07 '19 at 16:02

2

the value of (dec & 0x8000) != 0 is evaluated first as true or false(1 or 0) and then bit is assigned the value.

answered Apr 07 '19 at 16:02

Sandeep Polamuri

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score 1 · Answer 3 · edited Apr 07 '19 at 18:02

1

This line takes the number you inserted from console and applies logical AND. For example, if you enter 1024 ( 0100 0000 0000 binary ), then you have 0100 0000 0000 & 1000 0000 0000 0000 ( which is 0x8000, every number is replaced with binary tetrad ). In this case result is 0 which isn't != 0 and then value of variable bit is 0.

edited Apr 07 '19 at 18:02

Federico klez Culloca

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answered Apr 07 '19 at 16:02

java_brat

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score 0 · Answer 4 · answered Apr 07 '19 at 16:10

The & operator is bitwise-and. It is being used to mask off all bits from dec except bit 0x8000. The != operator is a comparison operator. It tests for two values being unequal. If they are unequal, the result is 1. Otherwise the result is 0. So if bit 0x8000 of dec is non-zero, i.e. 1, then bit will be 1. Otherwise it will be 0.

score 0 · Answer 5 · answered Apr 07 '19 at 16:34

0

It tests if the single bit set in the constant 0x8000 is set in dec or not. & is the bitwise and operator.

The result of (dec & 0x8000) != 0 (which is either 0 or 1) is assigned to bit.

Personally I prefer bit = !!(dec & 0x8000).

answered Apr 07 '19 at 16:34

Bathsheba

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score 0 · Accepted Answer · answered Apr 09 '19 at 11:34

The line

bit = (dec & 0x8000) != 0 ;

is equivalent to:

if ( (dec & 0x8000) != 0 ) bit = 1;
else                       bit = 0;

but it is an one-liner for the if-else statement

& is the bitwise and operator which compares the binary record from dec and 0x8000 and returns the 1's where there are both in dec and 0x8000

little example: 11&5 returns 1 because 11 = 0b1011 and 5 = 0b101 and comparing (from right to left) we have only the last 1 in both numbers...

0x8000 is hexadecimal for 32768

hope this will help

operators = and != in the same time

6 Answers6