What is binary?

Why do computers use it?

The first computer was NOT a binary machine

.. but that was a mistake

Which is clearer?

Which is clearer?

Confident?

recursive

89635839

010011010

How binary works

To convert to decimal, just add them up!0*128 + 1*64 + 0*32 + 1*16 + 1*8 + 1*4 + 1*2 + 0*1

0

Units (1s)

1

2s

1

4s

1

8s

1

16s

0

32s

1

64s

0

128s

Just two numbers, 0 and 1 Place matters

Can you do it?

Decimal number 128 64 32 16 8 4 2 1

0 0 0 0 0 1 1 0

0 1 0 0 0 1 1 1

0 0 0 0 0 0 0 0

0 1 0 1 0 1 0 1

1 0 1 1 1 1 0 1

0 0 1 0 1 0 1 1

1 1 1 1 1 1 1 1

Can you do it the other way?

Decimal number 128 64 32 16 8 4 2 1

6

7

15

23

62

127

96

What’s the bottom of Excel?

Excel binary to decimal

Use eight cells for the binary number

Put the magic numbers below: 128,64,32,16,8,4,2,1 Multiply * Add the results =sum() Make it look good

Can you do it the other way round?

Excel decimal to binary

Use =div() to divide by two Keep doing it Use =mod() to find the remainder That gives you the binary digits

Decimal number here=int(/2)

=mod(,2)

Can you ….

Write out a binary number? Convert binary to decimal? Convert decimal to binary? Use multiply in a spreadsheet? Drag-Copy in a spreadsheet? Use =SUM() in a spreadsheet? Use =INT() in a spreadsheet? Use =MOD() in a spreadsheet?