Clear all bits from LSB to ith bit

C programming, Interview questions, C programming Interview-questions,

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YasminRadwan26

2022-06-25

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Answer:

To clear all bits of a data from LSB to the ith bit, we have to perform AND operation between data and mask (flag) having LSB to ith bit 0.

To create a mask, first left-shift 1 (i+1) times.

mask =(1 << (i+1)); // give you 00001000

Now if we minus 1 from that, all the bits from 0 to i become 1 and remaining bits become 0.

mask = mask – 1 ; // give you 00000111

After that perform complement operation on the mask, all the bits from 0 to i become 0 and remaining bits become 1.

mask = ~mask; //give you 11111000

Now just simply perform anding operation between mask and data to get the desired result.

data = data & mask; // Now bits are clear from LSB to ith position

#include <stdio.h>
int main()
{
    unsigned int mask = 0; // mask flag
    unsigned int i = 2; // ith position till u want to clear the bits
    unsigned int data = 15; //value of data
    mask = (1 << (i+1)); //Shift 1 ith position
    mask = mask -1 ; //give us 00000111
    mask = ~mask; //give us 11111000
    //Now clear all bits from msb to ith position
    data  = data & mask;
    printf("data = %d\n", data);
    return 0;
}

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Clear all bits from LSB to ith bit

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