Wikipedia:Reference desk/Archives/Computing/2007 November 22

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1 November 22

[edit] November 22

[edit] what does a speed of 54 kb/s means?

If you have a modem 54kb/s you just get 4-5 kb/s. Why do you call it 54kb/s if you only get 10% of it? —Preceding unsigned comment added by Mr.K. (talk • contribs) 04:45, 22 November 2007 (UTC)

56kbps is the maximum theoretical speed over a conventional phone line- I believe it's capped by legislation in fact. It's by no means a guarantee. Also I think you're probably getting 4 or 5 KB/s, which is maybe 35kbps.. I doubt your ISP could get away with just 4 or 5 --⁪ffroth 04:51, 22 November 2007 (UTC)

Ah, yep it is regulated, by the good old FCC </sarcasm> --⁪ffroth 04:53, 22 November 2007 (UTC)

There is usually a confusion of the units. Modem speeds are usually advertised in kilobits per second. Transfer speeds are usually measured in kibibytes per second. If you have 54kbps (kilobits per second), that is 54 000 bps (bits per second), which is 6750 B/s (bytes per second), which is about 6.59 KiB/s (kibibytes per second). So 4 or 5 KiB/s is not that far off. --Spoon! (talk) 05:10, 22 November 2007 (UTC)

The kilo/kibi probably isn't very significant for a general approximation though- the main issue is that 56k means 56k bits per second, not 56KB/s --⁪ffroth 06:38, 22 November 2007 (UTC)

Actually, it's neither bits not bytes. The 'b' stands for 'baud'. What's more, 'baud' is a measure of the number of 'signalling events' per second - so you shouldn't be talking about kb/s - just kbaud. Because bytes are sent using a serial protocol, you'll generally need 10 signalling events to send one byte (depending on whether you are using 7 bits per byte or 8, one or two stop bits and with or without parity - the typical 8N1 setting needs 1 start bit, 8 data bits, no parity and 1 stop bit - 10 signalling events to send 8 bits). So at best, a 54kbaud modem sends 5.4 kbytes per second. However, that's only possible on an absolutely perfect quality phone line - which you'll almost never have. In practical terms, the modems at the two ends of the line have to negotiate a rate that allows both of them to get clean data through - and they do this by trying to send data at various set rates until they find one that works well that they can both cope with. This may be 28.8kbaud or 14.4kbaud or 9.8kbaud or worse. But most phone lines can manage 14.4 kbaud - which is 1.44 kbytes per second. So I'd say that if you are getting between 4kbytes and 5kbytes per second, you are doing very well. SteveBaker (talk) 07:21, 22 November 2007 (UTC)

I thought with all-digital phone lines these days, you're basically guaranteed a consistent baud-byte --⁪ffroth 07:39, 22 November 2007 (UTC)

A modem doesn't care whether the underlying transmission technology is digital or analog - it encodes binary data as audio - whether the phone service subsequently encodes the audio digitally or not is irrelevent to the modem. SteveBaker (talk) 19:52, 23 November 2007 (UTC)

Maybe the old 500 baud phone-on-cups modems, but I'm fairly sure nowadays that fully-integrated modems can handshake with the phone system and degrade performace based on whether there are any slower analog segments between it and the destination --⁪ffroth 21:29, 23 November 2007 (UTC)

You have a strange idea of how telephony works! All modems since about the 9800 variety have had the ability to negotiate the best data rate for the phone line quality - but that's not the same thing as using a digital phone line digitally. There is simply no way to do that through a standard telephone jack. Sure, if it's a digital line, you'll get better quality and higher data rates will result from the negotiation phase - but it's not because the modem somehow knows it's a digital phone line - it's because the audio quality is just generally better so the 'negotiation' process works better. There are all sorts of ugly phone-related problems that modems have to work around - even with a mostly digital connection. For example, when you talk into a telephone, it feels more natural if you can hear your own voice coming out of the speaker. (This is called 'side tone') Annoyingly, this feature is provided by the telephone exchange reflecting a little bit of your own audio back at you (kind of like an echo) - this has to happen even on digital phone lines. That 'echo' is really annoying for modem designers and they have to have all sorts of ikky 'echo cancellation' circuits in them so they can distinguish their own echo from the modem tones sent by the other computer. A truly digital solution (like DSL) avoids all of those problems - which is why DSL produces such vastly superior data rates down the exact same copper wires as regular telephony. SteveBaker (talk) 08:34, 25 November 2007 (UTC)

ITU-T V-Series Recommendations#Simultaneous transmission of data and other signals says the contrary, it says it's 56kbits/s. --antilived^{T | C | G} 07:45, 22 November 2007 (UTC)

Contrary to me or steve? --⁪ffroth 07:59, 22 November 2007 (UTC)

Steve. --antilived^{T | C | G} 08:05, 22 November 2007 (UTC)

I believe a baud is a singla signalling unit -- a tone, if you will. At 1200bps modem is actually a 600 baud modem, but each baud encodes two bits by being one of four different tones. However, as is obvious from the above discussion, there's been a lot of confusion about the term. --Mdwyer (talk) 17:36, 23 November 2007 (UTC)

[edit] Ubuntu exim4 TLS problem

Hi, can anyone out there help me - I've got a mail server running Ubuntu and exim4 and I can't get TLS to work. I've tried setting it up as described in several howtos, but I can't get it to advertise STARTTLS :(. My configuration is default for ubuntu except as follows:

A file named 00_localconfig in the "conf.d/main" directory with the following:

   MAIN_TLS_ENABLE = "yes"
   SYSTEM_ALIASES_PIPE_TRANSPORT = address_pipe

and the debian/ubuntu config file update-exim4.conf.conf with the following (identifying features obfuscated with generic type info):

  # /etc/exim4/update-exim4.conf.conf
  # 
  # Edit this file and /etc/mailname by hand and execute update-exim4.conf
  # yourself or use 'dpkg-reconfigure exim4-config'
  #
  # Please note that this is _not_ a dpkg-conffile and that automatic changes
  # to this file might happen. The code handling this will honor your local
  # changes, so this is usually fine, but will break local schemes that mess
  # around with multiple versions of the file.
  #
  # update-exim4.conf uses this file to determine variable values to replace
  # the DEBCONFsomethingDEBCONF strings in the configuration template files.
  #
  # Most settings found in here do have corresponding questions in the
  # Debconf configuration, but not all of them.
  #
  # This is a Debian specific file
   
  dc_eximconfig_configtype='internet'
  dc_other_hostnames='mail.domain.com : www.domain.com : domain.com '
  dc_local_interfaces=
  dc_readhost=
  dc_relay_domains=
  dc_minimaldns='false'
  dc_relay_nets='192.168.0.0/16'
  dc_smarthost=
  CFILEMODE='644'
  dc_use_split_config='true'
  dc_hide_mailname=
  dc_mailname_in_oh='true'

gnuTLS is also installed, and this:

   sudo swaks -a -tls -q EHLO -s localhost -au example@example.com -ap '<>'"

gives me this:

   swaks -a -tls -q EHLO -s localhost -au example@example.com -ap '<>'
   === Trying localhost:25...
   === Connected to localhost.
   <-  220 mail.domain.com ESMTP Exim 4.62 Thu, 22 Nov 2007 20:30:05 +1100
    -> EHLO mail.domain.com
   <-  250-mail.domain.com Hello root at localhost [127.0.0.1]
   <-  250-SIZE 52428800
   <-  250-PIPELINING
   <-  250 HELP
   *** STARTTLS not supported
    -> QUIT
   <-  221 mail.domain.com closing connection
   === Connection closed with remote host.

Any suggestions of fixes, diagnostics or ways of acquiring effective divine intervention would be welcome!

--Psud (talk) 09:46, 22 November 2007 (UTC)

Oh, and running this as root:

  exim4 -d

gives me:

   Exim version 4.62 uid=0 gid=0 pid=18767 D=fbb95cfd
   Berkeley DB: Sleepycat Software: Berkeley DB 4.3.29: (September  6, 2005)
   Support for: crypteq iconv() IPv6 PAM Perl GnuTLS move_frozen_messages Content_Scanning Old_Demime
   Lookups: lsearch wildlsearch nwildlsearch iplsearch cdb dbm dbmnz dnsdb dsearch ldap ldapdn ldapm mysql nis nis0 passwd pgsql
   Authenticators: cram_md5 cyrus_sasl plaintext spa
   Routers: accept dnslookup ipliteral iplookup manualroute queryprogram redirect
   Transports: appendfile/maildir/mailstore/mbx autoreply lmtp pipe smtp
   Fixed never_users: 0
   Size of off_t: 8
   changed uid/gid: forcing real = effective
     uid=0 gid=0 pid=18767
     auxiliary group list: <none>
   configuration file is /var/lib/exim4/config.autogenerated
   log selectors = 00000ffc 00089001
   cwd=/etc/exim4 2 args: exim4 -d
   trusted user
   admin user
   changed uid/gid: privilege not needed
     uid=106 gid=112 pid=18767
     auxiliary group list: <none>
   user name "root" extracted from gecos field "root"
   originator: uid=0 gid=0 login=root name=root
   sender address = root@domain.com
   Exim is a Mail Transfer Agent. It is normally called by Mail User Agents,
   not directly from a shell command line. Options and/or arguments control
   what it does when called. For a list of options, see the Exim documentation.

—Preceding unsigned comment added by Psud (talk • contribs) 09:53, 22 November 2007 (UTC)

I don't know specifically about your problem, but perhaps you can read the Exim4 page on the Ubuntu community documentation. --Spoon! (talk) 02:08, 23 November 2007 (UTC)

It's cool. Problem seems to have sorted itself out when I threatened the system with reinstallation --Psud (talk) 13:38, 23 November 2007 (UTC)

[edit] HOW IS WEIQI RELATED TO CHESS

? —Preceding unsigned comment added by 218.186.9.2 (talk) 11:02, 22 November 2007 (UTC)

They are both board games of ancient Asian origin. I'm not aware of any closer relationship; the gameplay is completely different. Our article on weiqi (usually known in the west as Go) contains some comparison between the two.

(I'm not sure what this is doing on the computing reference desk.) TSP (talk) 14:50, 22 November 2007 (UTC)

[edit] IC's :What does 74(series) temperature range mean ?a

What does 74(series) temperature range mean ,and how is different from 54 series?

11:11, 22 November 2007 (UTC)59.92.139.115 (talk)shashank

The 7400 series article has a little bit on this, although it doesn't include any actual specs. --tcsetattr (talk / contribs) 19:14, 22 November 2007 (UTC)

5400 is military temp range -40 to +85 operating. Transistor-transistor logic —Preceding unsigned comment added by TreeSmiler (talk • contribs) 03:50, 23 November 2007 (UTC)

[edit] software programs

features and functions of benchmark —Preceding unsigned comment added by 196.220.4.57 (talk) 12:51, 22 November 2007 (UTC)

`````` —Preceding unsigned comment added by 196.220.4.57 (talk) 12:53, 22 November 2007 (UTC)

Check out Benchmark (computing) and let us know if there are additional questions. --— Gadget850 (Ed) ^talk - 13:12, 22 November 2007 (UTC)

Or a question in the first place.. --⁪ffroth 21:26, 23 November 2007 (UTC)

[edit] computer

I want to know the object orientation that are present in microsoft access. —Preceding unsigned comment added by 82.206.136.70 (talk) 13:10, 22 November 2007 (UTC)

That's sort of a broad question. Access uses VBScript as its core scripting language and is pretty much as object orientated as Visual Basic 6.0 (not VB.NET) would be, though most of the database stuff is automatically instantiated so you don't have to do it manually. Do you have a more specific question? --24.147.86.187 (talk) 18:12, 22 November 2007 (UTC)

[edit] When running DOS programs(Clipper program) in windows xp screen shrinked to half why?

I am a Clipper Programmer. When I am running one of my Clipper programs in windows xp the usual full screen menu is shrinked to half screen. What is the reason for this distortion? What is the remedy?. Please help 59.88.73.103 (talk) 16:04, 22 November 2007 (UTC)psnyasas

It's generally a bad idea to run DOS programmes under XP, try using DosBox instead. --antilived^{T | C | G} 21:36, 22 November 2007 (UTC)

A full screen command prompt in Windows XP uses a text mode with more lines on the screen than the standard 25 lines from old DOS days. If this is what you are referring to, I found two alternative ways you can change it:

Enter mode con: lines=25 at the command prompt.
In the system menu, choose Properties, then click on the Layout tab. In the Screen Buffer Size section, enter the Height as 25. --Bavi H (talk) 03:48, 23 November 2007 (UTC)

[edit] Text size problem

After a recent reinstall of Vista Home Premium, my IE7 is having trouble with wiki sites such as Wikipedia. All text is displayed at half the size of how it should be with double the amount of space between lines. This is not an issue relating to my text size or page zoom settings, and does not affect other browsers from what I can tell (Firefox works normally). Can anyone suggest a solution?Martin Leng (talk) 19:34, 22 November 2007 (UTC)

That sounds odd. Have you tried emptying your cache, first of all? --140.247.11.24 (talk) 19:57, 22 November 2007 (UTC)

Have you tried not caring how much IE7 wants to screw itself up? Just stick with firefox.. --⁪ffroth 21:26, 23 November 2007 (UTC)

[edit] Laptop memory upgrade

Current configuration:

Compaq Presario V5209US
Hynix HYMP564S64BP6-Y5AB 0622

Memory that I plan to buy:

Kingston 2GB (2 x 1GB) 200-Pin DDR2 SO-DIMM DDR2 667 (PC2 5300) Dual Channel Kit Notebook Memory
200-Pin DDR2 SO-DIMM
KVR667D2K2SO/2GR
Capacity: 2GB (2 x 1GB)
Speed: DDR2 667 (PC2 5300)
Cas Latency: 5
Voltage: 1.8V
ECC: No
Buffered/Registered: Unbuffered
Heat Spreader: No

Is the Kingston 2GB (2 x 1GB) 200-Pin DDR2 SO-DIMM DDR2 667 (PC2 5300) Dual Channel Kit Notebook Memory compatible with my laptop? -- Toytoy (talk) 21:48, 22 November 2007 (UTC)

I don't know for sure, but here is the Crucial.com page for your computer which describes the types of memory that are compatible with it. From what I can tell what you are describing seems identical to this RAM, which is compatible with your system, so it should work. --24.147.86.187 (talk) 02:57, 23 November 2007 (UTC)

[edit] Microsoft Sam

How come it doesn't say 'soy' right? —Preceding unsigned comment added by 84.66.155.90 (talk) 22:11, 22 November 2007 (UTC)

It's pretty old. Try typing in "soif". Lots of fun to be had with that glitch. NIRVANA2764 (talk) 02:12, 23 November 2007 (UTC)

And "crotch". I wish I had Microsoft Bob- Vista comes with stupid Microsoft Anna --⁪ffroth

Zoy is a pretty good alternative for soy. Stewy⁵⁷¹⁴ talk 23:13, 23 November 2007 (UTC)