# How Many Bytes in a Kilobyte?

Discussion in 'Computing and ICT' started by JaquesJaquesLiverot, Nov 11, 2015.

?

## How many bytes in a kilobyte?

1. ### JaquesJaquesLiverotEstablished commenter

Having learnt most of what I know prior to 1998, I've always taught that a kilobyte is 1024 bytes, with a megabyte being 1024 x 1024 bytes, etc.

I was just looking at the Edexcel GCSE Computer Science specimen paper, and there was a question about calculating the number of bytes in a Gigabyte, which suggests that Edexcel agrees with me.

According to the Wikipedia article on the kilobyte, however, the IEC defines the kilobyte as 1000 bytes, and 1024 bytes is a kibibyte, which I'd never heard of. Apparently this was agreed in 1998.

What do you tell your students? Do you mention that it's an area of contention?

2. ### spartacus123Occasional commenter

How many bits in a byte? 8 bits = 1 byte, 1024 bits = 128 bytes

Kilo means 1000. So a kilobyte = 1000 bytes = 128,000 bits

But a part of me wants to say it's 1024 bytes.

Luckily I don't have to teach this thing.

I always used to tell them both, with the caveat "1024 is more widely used and is what the exam board requires"

5. ### NeitherMouseNorSockNew commenter

I maybe wrong but I'm pretty sure I read at some point that measuring speed was base 10, measuring storage was base 2?

6. ### tjraOccasional commenter

I haven't read this so can't confirm, but someone in the Edexcel Computing Facebook group was complaining that the examiner had not accepted 1000 but was demanding it be listed as 1024. I teach mine that it's 1024 anyway but it's still a bit worrying that it seems they're asking for the wrong answer!

7. ### itgeekNew commenter

New one on me as well. I always used to refer to and explain the actual maths in binary 1024 etc however clarify that for marketing purposes particularly in data communications 10M or 1G or whatever is used. Not quite sure what to say, probably get clear guidance from your exam board as to what they accept.

8. ### gnulinuxOccasional commenter

The difference between KiloByte and kibibyte has been known for ~15 years. Any Linux use will be able to tell you. The problem lies with exam boards and their advisors who clearly don't know the details of the subject they are supposed to be responsible for.

9. ### JaquesJaquesLiverotEstablished commenter

I've been using Linux for at least ten years and it was news to me - where in "Linux" does the term kibibyte appear?

BrianUK likes this.

As it would seem from this article that any old fool can suggest naming conventions and being older and foolisher than most
Can I suggest we have

I was going to use
Kitty-nybbles, Moggy-nybbles and Tabby-nybbles
But thought that some would say I wasn't taking this discussion seriously enough

jbourne8 likes this.
11. ### spartacus123Occasional commenter

Kilobytes. Looks at HDD and sees it has a storage capacity of 3TB

Checks RAM - 8GB .

Remembers first computer. VIC20 . 5KB RAM. 16 colour choices!

That's when memory calculations become interesting. The good old days.

12. ### rubikwizardNew commenter

The new AQA A Level syllabus is very specific that students need to know the difference between kibi and kilo etc. I know people complain about the AQA syllabus but I really like how specific the specification is which allows the students to be better prepared for the exam.

Have a look at the image I have uploaded from the spec.

#### Attached Files:

• ###### units.PNG
File size:
146.1 KB
Views:
20
ICT Don likes this.
13. ### frank134New commenter

This is a useful article: http://blog.forret.com/2005/02/binary-confusion-kilobytes-and-kibibytes/. The author suggests that the technical definition is that 1,000 bytes equals 1 kilobyte but that a large portion of the computer industry still uses 1,024. Interesting, I just took a look at my Mac and, for storage at least, they are using the technical definition, i.e. I have 249,769,230,336 bytes of disk space and they are reporting it as 249.77 GB. P.S. This was all news to me too...

14. ### TonyGTEstablished commenter

As above, a kilobyte and a kibibyte are two different things.

A kibibyte is 1024 bytes
A kilobyte is 1000 bytes.

xilio is greek for 1000 hence kilobyte

15. ### TonyGTEstablished commenter

Edexcel is wrong (which wouldn't be the first time).

The only fair thing to do would be to either accept both 1000 and 1024 as correct answers (like Cambridge do) or just 1000 if they were to ask a question on how many bytes were in a kilobyte. The answer is never 1024

16. ### TonyGTEstablished commenter

This is a big problem throughout computer science in education.

17. ### JaquesJaquesLiverotEstablished commenter

That's not true - according to Wikipedia, JEDEC (whoever they might be) still define a kilobyte as 1024 bytes.

The strangest thing about this is that, prior to 1998, i.e. when most of us went to school, a kilobyte was 1024 bytes, so why did the IEC change the definition, rather than create new units? I know that it's for the sake of consistency with kilometer, etc., but as there's no mechanism for letting anyone know that the definition has changed (I just happened to come across it by accident 17 years later), it seems like it's asking for trouble.

18. ### ICT DonNew commenter

This is old hat...

http://arstechnica.com/uncategorized/2006/06/7174-2/

As TonyGT says, these inconsistencies between exam boards are a nightmare. No wonder people struggle to teach it correctly. When I last taught the A-level OCR used their own version of UML which is supposed to be a standardised design tool!

19. ### ICT DonNew commenter

Oh and rubikwizard is spot on. For everyone who moans about the AQA spec at least it's clear about what to teach!

20. ### JaquesJaquesLiverotEstablished commenter

Although, in that post-1998 case, the court obviously ruled that a kilobyte is 1024 bytes and that the Western Digital drives were under-sized because of "the world's failure to adopt these new terms means that the old binary definitions for kilobytes and megabytes should still stand."