1. Find Subtraction of 402 and 314 using 7's complement method

Here A = 402, B = 314.
Find A - B = ? using 7's complement
First find 7's complement of B = 314

Note : 7's complement of a number is obtained by subtracting all bits from 777.
7's complement of 314 is

	7	7	7
-	3	1	4
	4	6	3

Now Add this 7's complement of B to A

1
	4	0	2
+	4	6	3
1	0	6	5

Hints : (Move mouse over the steps for detail calculation highlight)

Step-1 `=2+3` `=2+3` `=5` `=8xx0+5` `=5_8` `:.` Sum`=5`	Step-2 `=0+6` `=0+6` `=6` `=8xx0+6` `=6_8` `:.` Sum`=6`
Step-3 `=4+4` `=4+4` `=8` `=8xx1+0` `=10_8` `:.` Sum`=0` and carry`=1`

The left most bit of the result is called carry and add it to the rest part of the result 065.

	0	6	5
+			1
	0	6	6

So answer is 066