# Binary

There are only 10 types of people in the world: those who understand binary, and those who don’t. – Unknown

## Converting Decimal to Binary

To convert decimal to binary:

- take your decimal number, n
- divide your number by 2 and save the dividend and remainder
- make the dividend your new number
- push the remainder onto a stack
- repeat this process until your number is 0
- pop all the numbers of the stack to create the binary number

Do this on paper. Stop to understand why the remainder will always be 1 or 0.

FYI: The above technique works with decimal to any base! Just change ‘2’ to the base you want to covert to.

```
# Returns a binary string
# you would never do this in a real program as Python has `bin(n)`
def decimal2binary(n):
nba = [] # n as binary array
div = n # dividend
while div != 0:
rem = div % 2
div = div // 2
nba.append(rem)
# list comprehension to reverse array and join elements as a string
return ''.join(str(i) for i in reversed(nba))
```

## REFERENCES

Day 10: Binary Numbers. 30 Days of Code. HackerRank.