﻿ NASA space tech: From Pioneer to Curiosity | ZDNet

# NASA space tech: From Pioneer to Curiosity

Summary: As Voyager celebrates its 35th birthday and Curiosity starts on the most exciting Mars mission ever, we look back at the IT under the hood of six NASA projects that have made science fiction into everyday fact.

Image 1 of 6

Topics: Nasa / Space, After Hours

Rupert started off as a nerdy lad expecting to be an electronics engineer, but having tried it for a while discovered that journalism was more fun. He ended up on PC Magazine in the early '90s, before that evolved into ZDNet UK - and Rupert evolved with them into an online journalist.

Kick off your day with ZDNet's daily email newsletter. It's the freshest tech news and opinion, served hot. Get it.

## Talkback

• ### Bits Bytes and nibbles

"...upgrade to 1 megabit (256kB) of chip memory ..."

How many bits were there in a Byte in 1974? :-)
• ### bits

8 bits to a byte I think... 4 bits were a nibble...
• ### Sheridan's quibble wasn't with the nibble...

...but with the author's erroneous math. 1 megabit does not equal 256kb. It's equal to 125kb.
• ### kB, I mean

Kilobyte. Typo.
• ### Far too subtle...

Yup, I was trying to nudge gently rather than scream abusively about a typo or mathematical inexactitute - I even added a 'smiley'. Guess I should just be direct in future but I can never resist the opportunity to use the much neglected 'nibble'.
I don't think it's ever used as an abbreviation as it could be confused with Newtons but, just perhaps...
1mb = 265kn = 128kB
• ### Byte

Hey guys, the Intel 4004 is/was a 4-bit microprocessor. And it was not written that a byte equals 8 bits. A byte is the basic addressable element in computer architecture, not necessarily 8 bits. It is hardware dependent and there is no official standard that dictates that a byte is 8 bits. So in this instance, the author is correct. One megabit is egual to 256 KB.
• ### Byte, undefined?

Hmmm... having checked the usual source, I have to agree that it isn't 'set-in-stone' that a byte is 8 bits. However, back in 1976 we were using substantial numbers of 8080s. 6800s, 6502s (and even a few Z80s) and the term byte was generally accepted as being 8 bits - as I suggest it is now.

While the term 'word' often needs clarification it is now usually thought of as 16 bits but some of us remember the PDP8 with words of 12 bits. Interestingly, the usual source quotes the 4004 as using '4 bit data words' (not bytes). However, Intel data for the 4004 refers to one word instructions being 8 bits and two word instructions being 16 bits - but I don't see them mentioning bytes anywhere.

So, Superbiker, I take your point regarding absolute definitions and I will even say; "Mea culpa". But... with the wide acceptance of byte meaning 8 bits, perhaps journalists could make it clear when they mean another size. I've never had to check that a hard disk or RAM that quotes the size in bytes means 8 bit per byte - and I hope I don't have to start now. (Bad enough that hard disks use powers of 10 while the rest of IT uses powers 2).

So, officially ??? -
bit = single binary digit (1 or zero)
nibble = group of four bits
octet = 8 bits or 2 nibbles
byte = one or more bits (context dependant)
word = one or more bits (context dependant)

I need to go and edit/clarify a lot of my documents - and try to work out if I've bytten more or less than I can nibble!
• ### One small correction

The Voyagers were sent to study Jupiter, Saturn, Uranus and Neptune, not Pluto. Pluto will be visited for the first time ever in 2015 by the New Horizons probe.