Geeks Part III

Re: Geeks Part III

If you are considering Chinese abaci with two levels there are two bases used, 5 and 2. IBM computers used base 2, base 5 computers are a mystery to me..

There is a name for it.

You are correct. Chinese & Japanese abaci use a hybrid base-2/base-5 encoding system. But there is a name for such a syetem.

Most modern computers use purely base-2 or 'binary' encoding. However, other encoding systems have been used.

At least one commercially produced computer used a hybrid base-2/base-5 encoding system.

BCD?

Not it.

The decimal digits on an abacus are segregated as in BCD (Binary Coded Decimal), but the encoding is not pure binary.

Don't Know the Name for the Code

I've used binary, octal, BCD, and EBCDIC.

My guess as to the manufacturer is either Univac or RCA. I don't think IBM did (or if they did it was well before 1965 when I started working with computers). Of course, Sperry is another possibility.

BobH

Set the Way-Back machine for 1953

In 1953, IBM decided that the world was ready for an 'affordable' computer. This machine sold for less than 1/2 million dollars and could fit into a simgle room.

OK. Are we Talkin' the 704?

Still don't know what character representation system it used (to include both numbers, alphabet, special characters, control characters, et al. that's what EBCDIC, BCD, and other systems do).

BobH

Before the 704

The encoding was very similar to a chinese abacus. Each decimal digit was represented by 7 bits. 2 of the bits had a value of 5 and the remaining 5 had a value of 1. Valid encodings consisted of exactly one bit from each set.

Decimal digits were represented as follows:

0 = 10-10000

1 = 10-01000

2 = 10-00100

3 = 10-00010

4 = 10-00001

5 = 01-10000

6 = 01-01000

7 = 01-00100

8 = 01-00010

9 = 01-00001

Apparantly, Univac used a variant of this encoding on a couple of early models as well.

Answer *LINK*

The numeric encoding scheme used on a chinese style abacus is called "bi-quinary" since it combines binary (base 2) and quinary (base 5) representations.

One early computer that used this system was the IBM 650.


IBM 650