Bit Manipulation

1. Bit Manipulation

2. Get Bit from the particular Position • Suppose you want to get a bit from the 4th position. • You can call • int get_bit_val(int number_send,int position) function. • In this function, number_send is our data from where we want to get a bit. Second pass the position from where you want to get a bit.

3. Get Bit function int get_bit_val(int number_send,int position) { int number1=1; number1=number1<<(position-1); if(number_send & number1) { return (1); } else { return (0); } }

4. How Get bit function works? • First argument we can pass as int. so ascii value is passed there as a number_send. • Suppose user has entered a character N that you pass as a argument to get bit function. • Ascii of N is 78 that is 1001110. • Second argument you pass for the 4th position bit.

5. 0 1 0 0 1 1 1 0 0 0 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 0 0 0 1 0 0 0 Contd. • In the first step number1 =1 is initialized. • Number_send Number1 Number1<<(position-1) : Number1<<3 • Number_send Number1

6. 0 1 0 0 1 1 1 0 0 0 0 0 1 0 0 0 Contd. • if((number_send & number1)) return (1); else return (0); • Number_send Number1 It will generate answer 0 or 1 as per the number_send value. In this case, it will generate 1. &

7. Set Bit function • Through this function, we can set the bit with our own value on the particular position. • The function • void setbit(int *data, int pos, int val) takes 3 argument one is data, second is position and third is the value which we want to set on the particular position in the data.

8. Set Bit Function • void setbit(int *data, int pos, int val) • { • int mask=1; • mask = mask<<(pos-1); • if(val==0) • { • mask=~mask; • *data=*data & mask; • } • else • { • *data=*data | mask; • } • }

9. How set bit function works? • First one variable mask is initialized with one then after it is shifted on the particular position. • Then if value which is passed as third argument, if it is 0 then mask is complemented. So, if we perform data & mask then it sets 0 on that position. • If value which we want to set is 1 then data is ored with 1 so it sets 1 on that position.

10. 0 1 0 0 1 1 1 0 0 0 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 0 0 0 1 0 0 0 Example • In the set bit function suppose arguments are for data N, position is 4 and new value what we want to set is 0. Initially it is • Data • Mask • After performing left shift for mask • Data • Mask

11. 0 0 0 0 1 0 0 0 1 1 1 1 0 1 1 1 0 1 0 0 1 1 1 0 0 1 0 0 0 1 1 0 1 1 1 1 0 1 1 1 Example • if(val==0) { mask=~mask; *data=*data & mask; } In our case value is 0, means we want to set 0 on 4th position. mask ~mask Then last operation is data & mask & =

12. Insert Bit • int ins_bit_pos(int number_send,int position,int value) { • int num1,num2; • num1=number_send; • num1=num1>>(position-1); • num1=num1<<(position-1); • num2=number_send-num1; • num1=num1<<1; • num1=num1 | num2; • if(value==1) • { • num1=set_bit_val(num1,position,value); • } • return (num1); • }

13. 0 1 0 0 1 1 1 0 0 0 0 1 0 0 1 1 0 1 0 0 1 1 0 0 0 1 0 0 1 1 1 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 1 0 • We want to add bit 0 on the 3rd position. • Suppose number_send is N. which is assigned to num1 in the first step. So, • Num1 • Num1>> (position-1) • Num1<<(position-1) • Num2 = number_send – num1 - =

14. 0 1 0 0 1 1 0 0 1 0 0 1 1 0 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 1 1 0 1 0 • num1= num1<<1 • num1= • Num1<<1 • num1 = num1|num2 • Bit 0 is set on the 3rd Position. | =