decimal # to binary #

So I'll just post some hints.

1. To Convert the base-2 number ABCDEFG to base-10, use the result of the formula:

G*2^0 +F*2^1 +E*2^3 +D*2^4 +C*2^5 +B*2^6 +A*2^7

See a pattern? Here's a hint: If the number was ZABCDEFG then the exponet for the two of the Z'th digit would be 8.

2. To convert from base-10 to base-2, use modulo arthimitic. For instance, to convert 243 to base-2:

N N\2 Remainder
243 121 1
121 060 1
060 030 0
030 015 0
015 007 1
007 003 1
003 001 1
001 000 1
Then the base-2 number is 11110011. Hint: you can use recursion to implement that function.

Hope that helps!