## HISTORY OF THE COMPUTER – HOW COMPUTERS MULTIPLY

When it comes to the Decimal system, the addition of zero after a number is the result when that number is multiplied by ten. For instance, when you add a zero to the end of the number ‘4’, it becomes ‘40’, which is 4 times 10. As a means of expanding this, the addition of two or three zeros is the same as multiplying the number by 100 or 1000 respectively.

**THE SHIFT REGISTER**

Computers make use of the binary system and here, one can multiply by 2, simply by putting a zero after the number. If that is the case, then 110 (2+4=6 decimal) now turns to 1100 (4+8=12 decimal). More zeros can subsequently be added and it can be multiplied by 4,8,16 and so on (decimal). This process of multiplication is known as ‘shifting’, as one or zero is moved to the succeeding bit position, the first-bit position is occupied by a zero.

**THE ALU**

When it comes to multiplication with logic elements, various techniques are implemented. These elements usually, are expressed in a logic diagram as a ‘black box’ identified as the multiplier. More complex logic diagrams will see these and other ‘black boxes’ like square roots, adders and so on, combined into one large ‘black box’ known as Arithmetic Logical Unit (ALU).

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