take binary value for each digit like 7=111,5=101, 6=110.then combine them in correct order 657=110101111.then split them that each split must present after four binary bits from right hand side like 1-1010-1111.then put the hexadecimal value for each splitted binary bits.the we get 1AF.
(657)8-(110 101 111)2
now make paring of four for hexadecimal from right to left
( 1 1010 1111)2
now add three 0 in left of 1 to make its four digit
so we get
(0001 1010 1111)2=(1 A F)16
convert 657 to base 8...6*8*8+5*8+7*1=431
represent 431 in base16 i.e l.c.m of 431 with 16.It gives remainder as 1, 10, 15 which is equal to 1, A, F...as A=10,B=11,....F=15
in hexadecimal representation the value which in greater than 9 is represented by alphabets , hence A = 10, B =11, C =12, D = 13, E =14, F = 15
the value of 1AF = 1 10 15
Since Fast Memory Access is less and every thing on computer is represented in binary form representation of no in binary takes too space so 3 bit binary no is group to Octet and 4 bit binary no group to hexadecimal....so the 657 BCD is 110101111 and divide the BCD into 4 bit binary we get Hexadecimal Number 1(1) 1010(A) 1111(E) i.e 1AF
657 in binary number representation can be written as 110101111
now we make group of 4 digits from right to left so it is shown as
1=0001
A=1010
F=1111