AS I know, QR code ISO standard have 2 types:
ISO/IEC 18004:2006
ISO/IEC 18004:2015
Suppose I have a QR code, how can I check its ISO standard?
Thanks everyone.
Related
In visualead.com qr-code generator there is option to choose how to fill the qr code.
There are two qr-codes:
https://i.stack.imgur.com/izGH6.png
https://i.stack.imgur.com/m0wX5.png
with same data that is encoded with same version=3, error correction level = M and mask=1. But then what makes this different dots distribution?
After multiple tests, I found out:
The QR-Code payload also depends on the data encoding. If you take UTF-8, the QR-Code will certainly look different than using Latin-1 (ISO-8859-1). If you set the QR-Code generator to encode the data the same way, the QR-Code will look the same.
So (for QR-Codes according to the standard) there needs to be:
same Data
same QR-Code version
same Mask pattern
same Error correction level
same QR-Code encoding (Numeric, Alphanumeric, Byte, ...)
same Data encoding (independent from QR-Code settings)
Edit: As mentioned by Mark Ambrazhevich in the comments of this answer, the QR-Code can be dependent of the following, too, keeping in mind that this violates the QR-Code standard (ISO/IEC 18004:2015): After the data has been inserted into the QR-Code, it has to be 'filled up' up to the limits. According to the standard, the placeholders 11101100 and 00010001 should be used alternating. But like Russ Cox discussed at https://research.swtch.com/qart:
(post-terminator patterns) [...] Technically that's a violation of the spec, which prescribes a specific repeating 2-byte fill, but if all the readers you care about don't check the fill, then I agree it produces much nicer codes.
According to Kevin Baker on the same site, many commercial QR-Code-Readers do not check the post-terminator-data.
I'm working on an article about traping sets in LDPC codes. In numerical result part, writers check their algorithm on Codes C1 and C2 which are the LDPC codes with girth 6 and block lengths 576 and 1056, respectively, used in the IEEE 802.16e standard, but I can't find the matrix of these two parity check codes. Can anyone help me?
You can get the standard here: https://standards.ieee.org/standard/802_16e-2005.html
It must contain all the information necessary (if it is actually part of the IEEE 802.16e standard).
I'm writing some code to convert an v4 ip stored in a string to a custom data type (a class with 4 integers in this case).
I was wondering if I should accept ips like the one I put in the title or only ips wiht no preceding zeros, let's see it with an example.
This two ips represent the same to us (humans) and for example windows network configuration accepts them:
192.56.2.1 and 192.056.2.01
But I was wondering if the second one is actually correct or not.
I mean, according to the RFC is the second ip valid?.
Thanks in advance.
Be careful, inet_addr(3) is one of Unix's standard API to translate a textual representation of IPv4 address into an internal representation, and it interprets 056 as an octal number:
http://pubs.opengroup.org/onlinepubs/9699919799/functions/inet_addr.html
All numbers supplied as parts in IPv4 dotted decimal notation may be decimal, octal, or hexadecimal, as specified in the ISO C standard (that is, a leading 0x or 0X implies hexadecimal; otherwise, a leading '0' implies octal; otherwise, the number is interpreted as decimal).
Its younger brothers like inet_ntop(3) and getaddrinfo(3) are all the same:
http://pubs.opengroup.org/onlinepubs/9699919799/functions/inet_ntop.html
http://pubs.opengroup.org/onlinepubs/9699919799/functions/getaddrinfo.html
Summary
Although such textual representations of IP addresses like 192.056.2.01 might be valid on all platforms, different OS interpret them differently.
This would be enough reason for me to avoid such a way of textual representation.
Pros
In decimal numerotation 056 is equals to 56 so why not?
Cons
0XX format is commonly used to octal numerotation
Whatever your decisions just put it on your documentation and it will be ok :)
Defining if it is correct or not depends on your implementation.
As you mentioned windows OS considers it correct because it removes any leading zeros when it resolves the IP.
So if in your program you set an appropriate logic, e.g every subset of the IP stored in your 4 integer class, without the leading zeros, it will be correct for your case too.
Textual Representation of IPv4 and IPv6 Addresses is an “Internet-Draft”,
which, I guess, is like an RFC wanna-be.
(Also, it expired a decade ago, on 2005-08-23,
and, apparently, has not been reissued,
so it’s not even close to being official.)
Anyway, in Section 2: History it says,
The original IPv4 “dotted octet” format was never fully defined in any RFC,
so it is necessary to look at usage,
rather than merely find an authoritative definition,
to determine what the effective syntax was.
The first mention of dotted octets in the RFC series is …
four dot-separated parts, each of which consists of
“three digits representing an integer value in the range 0 through 255”.
A few months later, [[IPV4-NUMB][3]] …
used dotted decimal format, zero-filling each encoded octet to three digits.
⋮
Meanwhile,
a very popular implementation of IP networking went off in its own direction.
4.2BSD introduced a function inet_aton(), …
[which] allowed octal and hexadecimal in addition to decimal,
distinguishing these radices by using the C language syntax
involving a prefix “0” or “0x”, and allowed the numbers to be arbitrarily long.
The 4.2BSD inet_aton() has been widely copied and imitated,
and so is a de facto standard
for the textual representation of IPv4 addresses.
Nevertheless, these alternative syntaxes have now fallen out of use …
[and] All the forms except for decimal octets are seen as non-standard
(despite being quite widely interoperable) and undesirable.
So, even though [POSIX defines the behavior of inet_addr][4]
to interpret leading zero as octal (and leading “0x” as hex),
it may be safest to avoid it.
P.S. [RFC 790][3] has been obsoleted by [RFC 1700][5],
which uses decimal numbers of one, two, or three digits,
without leading zeroes.
[3]: https://www.rfc-editor.org/rfc/rfc790 "the "Assigned Numbers" RFC"
[4]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/inet_addr.html
[5]: https://www.rfc-editor.org/rfc/rfc1700
How does the 68000 internally represent instructions.
I've read that there are different types of instructions: single effective operation word format instructions, brief and full extension word format instructions. The single effective operation word instruction seems to represent the instruction and the lower 6 bits of this instruction the addressing mode and register. Does this addressing mode and register tell you if there follows a brief or full extension word format instruction, which on his turn represents the operands for the instruction. Do you know a better manual than the 68000 programming reference manual.
Thanks in advance
The actual internal representation is a combination of "microcode" and "nanocode". The 68000 has 544 17-bit microcode words which dispaches to 366 68-bit nanocode words.
While this may not be what you wanted to know, this link may provide some insights:
http://www.easy68k.com/paulrsm/doc/dpbm68k1.htm
right, on m68000 indexed modes uses the brief extension. In "Address Register Indirect with Index (8-Bit Displacement) Mode" (d8, An, Xn), the BEW is filled with D/A (if Xn is a data or address register), Xn (the register number), W/L (to threat Xn contents as 16 or 32bits), scale to 0 (see note), and the 8-bit displacement.
on other hand, other modes, like the 16bit displacement, "Address with displacement" (d16,An) , the extension is only a word with the displacement.
the note is: brief extension word - m68k doesn't support the 2bits for scale so is set to 0; scale on BEW using the scale bits, and full extensions are only suported m68020,40,-> cpus. http://etd.dtu.dk/thesis/264182/bac10_19.pdf
I have heard about octal number system lately and i wanna learn about it.
My dumb teacher that i asked for it. Told me "its no more used, u dont need to learn" but no sire im pretty sure its still in use so i need to know!
If there is someone who can explain me the octal number system and show me a way to convert it to Decimal(number system that we use in life) "it would help me to learn about it a lot" and where i can use it in life so i can show smt to that dumb teacher that he is wrong, that he must do his job on teaching..
i wanna do it on vb6, cause my teacher works on vb6 usually.
You can get more about Octal from Wiki - http://en.wikipedia.org/wiki/Octal
The octal, or base 8, number system is a common system used with computers. Because of its relationship with the binary system, it is useful in programming some types of computers.
Decimal, hexadecimal, and octal representations are straightforward. To read a string in these formats, use CLng.
Dim value As Long
value = CLng(Text1.Text)
Hexadecimal strings should begin with &H and octal strings should begin with &O.
To convert a value into a decimal, hexadecimal, or octal string representation, use Format$, Hex$, and Oct$ respectively. For example, Oct$(256) returns the octal representation of the value 256 (which is "400").