Opening a file by Autodesk Vault Explorer. This opens a new drawing based on the default drawing template file. When opening a drawing file in AutoCAD, the process takes a long time. L'inscription et faire des offres sont gratuits. Thanks for your help! Apr 16, 2024 · Type STARTUP in the command line and confirm with ENTER. I'm not sure why this started, but could someone provide some guidance on making this stop? Oct 8, 2023 · Repair the drawing in the older version of AutoCAD that is able to open it. The default behavior of AutoCAD is to open a drawing in the already running instance. I have the display setting at "extend these displays" under multiple displays. One or more of the following may also occur: AutoCAD is frozen while it loads the drawing but recovers when the file opens. Thanks dude, this helped me a lot!!! Solved: Hi My colleagues Autocad is relaunching itself everytime he opens a drawing. Even though it is not recommended, when changing the DWG file association from AutoCAD DWG Launcher to AutoCAD Application, this issue might go away. If I'm inside AutoCAD and choose File, Open, etc then the new drawing opens in the same AutoCAD program. Do not open a drawing. The value of SDI is set to zero. Change the setting to the AutoCAD DWG Launcher instead of the Acad. Mar 16, 2024 · Products: When opening a drawing file in AutoCAD, the process takes a long time. The user interface (workspaces or profiles). Click on Details, select AutoCAD open in the list and click the 'Modify' button. Opening multiple instances of AutoCAD can be done by launching the program again. (A Double-click can be seen as a double-click on the Acad. I've looked at SDI and that's set to 0. Palettes or toolbars (layers, tool palettes, toolbars, the ribbon). Switch to the layout to recover. The DWG file type association is invalid or incorrect in the Windows operating system. dwg files. Click on the FILES tab. The wrong graphics card is being used Jul 7, 2016 · My understanding is that you are running AutoCAD 2014 on the Windows 7 64 bit Operating System and you wish to know how to launch AutoCAD without a new drawing (drawing1. If I click on three drawings, AutoCAD has three different AutoCAD programs running. Either method chosen, I'd like to know if another 'blank On the Start tab, click New. I have written a program th Mar 4, 2008 · In 2004, if you had a drawing. I have this problem as well. Question and Answer for the Review Question at the end of Chapter 2 Book: AutoCAD and Its Applications, Comprehensive, 2012. Mar 8, 2024 · When double-clicking or opening a DWG file in Windows Explorer or from other third-party file-managing systems to open in AutoCAD product, a new instance of AutoCAD product is launched, resulting in opening multiple sessions of AutoCAD. By default, SDI is set to 0, allowing multiple drawings in one session (MDI mode). If you set it to 2, no file will open in AutoCAD but you will have to actively seek/start OPEN command to go hunt for your file. You think you get it set the way you want and it eventually changes. exe) Chercher les emplois correspondant à Autocad opens new session every drawing ou embaucher sur le plus grand marché de freelance au monde avec plus de 23 millions d'emplois. Edit the keys OpenDdeSvc and PrintDdeSvc to both have the value of AutoCAD. I have already set . All groups and messages Apr 12, 2021 · #AutoCAD #Autodesk AutoCAD 2022 has been released. Let's see what happens! We will also do a review on wh Aug 31, 2014 · The Autocad Shell Launcher always remembers the last Autocad program which opened a file. May 18, 2017 · Starts a drawing without defined settings. Use one of May 18, 2024 · For AutoCAD 2018 and earlier, type SDI on the command line and set the value to 1. Aug 21, 2013 · I am new to Plant 3D but I've been using AutoCAD for a while now. May 27, 2024 · After starting up or opening AutoCAD, the program seems to load (the application window and the Start Tab appear) but then it hangs or freezes. Windows 11. If the drawing has more than one layout, the user has to manually saveas, delete unwanted layouts and then bind/purge yada yada. dwg is opened in AutoCAD instead of the intended file. I just one be able to click on file and have it open in new tab of my exicting autocad window. I can open separate sessions of AutoCAD in View separate drawings side-by-side. It should just open the 2nd drawing in the - already open - autocad. NET) Parent topic: Control the AutoCAD Environment (. Aug 24, 2021 · How to control the opening of Single and Multiple drawings in AutoCAD?Solution:This feature is controlled by SDI (Single Document Interface) system variable. The following are possible AutoCAD (LT) opens drawing in new AutoCAD session Sep 2, 2020 · with an ACTIVE AutoCAD session running, I would double click a file outside of AutoCAD from a folder. Alternatively, open each drawing file in its instance of AutoCAD. However I just want to see one AutoCAD window and from AutoCAD I can switch between drawings. dwg) opening when double-clicking a file via Windows Explorer. For e. Apr 9, 2024 · I see you are visiting as a new member of the Civil 3D forum. The first item under there defines where ACAD looks for dwt files. It's not. dwg". There is a system variable called SDI (this stands for Single Document Interface) the toggle for this is 0 off and 1 on Apr 18, 2024 · Message 3 of 11. Solved: I am having an issue with AC2019 where, while using sdi - 1, we cannot open new sessions through windows explorer. The Open method opens an existing drawing file. I'm having a problem whereby new drawings open in different windows (see image "Actual Configuration"), but I'd like them to open in different tabs (see image "Desired Configuration"). Each instance can be managed separately and should show only on the virtual desktop where it is placed. The Start tab is displayed. Drag and drop the drawing into the AutoCAD Drawing Window. (I have AutoCAD LT 2016, although it EXERCISE 2-1 SETTING UP A DRAWING. Maybe deleting the layout and removing the predefined page-setups could be a good start for that. I have recently installed autocad 2019 ( instaed of 2018) and now every time i open a . Create a drawing. The following are causes of this issue: Installation AutoCAD product is not up to date. Then, launch a second instance of AutoCAD from the Start menu or desktop shortcut and use the OPEN command to open a second drawing. The drawing fails to load. This can also occur from the Vault Client, or from other third-party file-managing systems, when trying to open in AutoCAD. Step 1: Click the AutoCAD desktop icon to open the The acaddoc. g. Problem: AUTOCAD (LT) is already open. The program window is black or blank while the file opens May 7, 2024 · When double-clicking a DWG file, a blank drawing titled Drawing1. exe task and end it. If you set SDI to 1 (Command line: SDI 1), AutoCAD will only allow one drawing to open per session. That speeds up the startup of the program and is way more confortable. ToInt16 (Application. This behavior occurs because the SDI system variable is not set to its default value, which is 0. Right-click a file tab, and choose New to display the Select Template dialog box May 2, 2019 · To do this, open AutoCAD to a new blank drawing, and type at the AutoCAD command-line: (findfile "acaddoc. Apr 4, 2023 · AutoCAD 2024 Issue Opening Files. exe. Right-click on the file tab of the drawing you want to open in another session and click Move to New Session. This may also occur when double-clicking a DWG file from Vault. Run the -PURGE command. I'm looking for an proficient Autocad designer who can create structure drawings for a medium-sized office building (1,000 - 5,000 sq ft) with an open-plan layout, following plans provided: Ideal skills and experience: - Proficiency with Autocad software - Experience with office space design - Able to create simple structures - Ability to Apr 28, 2020 · Find the 'Opens with' part, Click the [ Change ] button. This is a behaviour specific to AutoCAD and no other application so can only assume that this is being driven by AutoCAD. - alfred -. layouts and then bind/purge yada yada. This means if you open another drawing, AutoCAD will prompt you to close the current one. it has to do with the application assigned to opening a . The Start tab is displayed and the ribbon is pre-loaded when you open or create a new drawing. exe /ACADLT. it would then open a NEW session of AutoCAD but abandon the opening of the file. On the Details tab, look for the AcIvServerHost. If the program is already running, the drawing opens in the current session rather than in a second session. Note: It is recommended to have only one session of AutoCAD running and only one drawing open All groups and messages Jun 27, 2017 · At the command line, type OPTIONS. Run the AUDIT and PURGE commands. Scroll down to the DWG file type. r23. Now "Start Drawing" and the plus (+) file tab will open this same file going forward. Change the value to either 2 or 3. " This won't prevent other folks from commenting on this question though, in the event AutoCAD (LT) opens drawing in new AutoCAD session Oct 8, 2023 · On the command line in AutoCAD, enter TASKBAR. Also: The freeze may occur on its own, or it may happen after clicking anywhere on the program window or on the Start Tab. When Use DDE is selected, the DDE Message should be set to [open ("%1")] and Theme to System . If a default drawing template file is not specified, the Select Template dialog box is displayed, from which you can choose an appropriate drawing template file. Entering 0 displays only the name of the current drawing. The problem is: everytime I open a new drawing. Confirm that it is set to 0. A dialogue should come up (AutoCAD - DWG Association). It's free to sign up and bid on jobs. May 27, 2016 · Dear Sir/Mam, This is to find solution for a problem with my Autocad 2016. 2008-05-13, 11:57 AM #3. Navigate to and select: HKEY_CURRENT_USER\Software\Autodesk\DwgCommon\shellex\apps\ {F29F85E0-4FF9-1068-AB91-08002B27B3D9}: AutoCAD. Other symptoms: After registration DWG file to AutoCAD DWG Launcher, it starts to open as DWG TrueView new instance. GetSystemVariable ("DBMOD")) Topics in this section. exe / ACADLT. lsp") If this returns a valid filepath, in the steps that follow, navigate to the filepath and open & modify the existing acaddoc. Use either the Save or SaveAs method to save a drawing. Dec 12, 2017 · AutoCAD is Opening new Drawings in a separate windows by default? We can help you Fix this behavior with just 2 simple commands! Oct 3, 2019 · Exit all instances of AutoCAD. You should have two files open. On your desktop go to your Windows Start. When the Acad. In Windows File Explorer, double-clicking to open an existing DWG opens a new drawing from template "Drawing1" in addition to the subject drawing in AutoCAD Products The DWG file type is associated to acad. If the above expression returns nil, open Windows The Add method creates a new drawing and adds that drawing to the Documents collection. NET) Work With No Documents Open (. AutoCAD (LT) opens drawing in new AutoCAD session Oct 8, 2023 · Double-clicking a DWG file launches a new instance of AutoCAD Mechanical 2020 or 2021. 1. Tip: Check the template path in Options so that AutoCAD goes to the right folder for Feb 12, 2021 · In this video, I'll show you how to rectify the problem where a DWG file opens in a new window rather than opening in a new tab of an already opened AutoCAD Apr 16, 2015 · Every time I open a drawing in AutoCAD it opens a new session. dwt) from the Files of Type: drop-down list and specify a template name and storage location. Mar 15, 2021 · In this video you will learn how to open an existing drawing file in Autodesk AutoCAD. Not C3D, but regular vanilla AutoCAD to continue cleanup. I glanced over my . If you find this video use Nov 22, 2013 · I can get all the cleanup done, and an export from Civil 3D to an AutoCAD 2013 format dwg. the two options available are. Then double-click a second one. AutoCAD Application. From Autocad help: taskbar. Start AutoCAD and select Start Drawing on the Start Tab to open a blank drawing. Select the correct file type at the bottom of the dialog box. Customized User Interface (CUI). In the bottom "Details of 'DWG' Extension" it should state "Opens with: AutoCAD DWG Launcher". You can copy the folder path from the Windows Exporer address bar and paste it into the open dialog box in AutoCAD and hit open to get you to the folder where the May 21, 2020 · When the hyperlink is called the drawing is loaded into either the open session of AutoCAD or a new session in opened but the AutoCAD window is positioned directly over the Excel window. This also applies when AutoCAD is started as an Ivanti VDX extended application. Watch me open it for the first time after install. Double-clicking or opening a DWG file starts a new instance of AutoCAD. NET) Save and Close a Drawing (. Aug 5, 2010 · application. Anyone got a solution ? Thanks in advance. It's the same window that appears when F2 is pushed. Oct 8, 2023 · When double-clicking a DXF file in Windows Explorer, a new instance of AutoCAD is launching. Causes: The SDI (Single Document Interface) system variable is set to 1. > 2008, if you do the same thing, it try to close the current drawing and just. Jun 15, 2019 · to run AutoCAD with the script, copy AutoCAD shortcut on your desktop, right click it and select properties, go to shortcut tab and copy and paste following characters to the end of the target field, not too close, leave one space there. Click Application menu Open Drawing. The SDI (Single Document Interface) system variable is legacy, and is maintained within the program for backward compatibility Jan 16, 2019 · a couple of months late but I think I might have a work around. Once the software freezes, launch the Windows Task Manager. Using multiple monitors. A full new autocad program starts opening. I have written a program that does it if Oct 8, 2023 · Solution: To work around this behavior, try the following: Set the command TASKBAR to 0. AutoCAD (LT) opens drawing in new AutoCAD session Jun 3, 2024 · User reported that when trying to open a specific drawing or template in AutoCAD products the program freezes or crashes. I'd like for that behavior to Apr 29, 2013 · Start AutoCAD, then find and select your file: if you set STARTUP command to 1, the prompt to go hunting for the file should open the same time as AutoCAD. Change the value to 1 to display a separate taskbar item for each open drawing. Hardware The graphics driver is out of date. Everytime i try to open a new DWG file, Autocad opens the same in a new session. DDE, (Items A and B in image below). If the drawing. With SDI equal to 1, double-clicking a DWG file in Windows opens a new instance of AutoCAD each time. The problem is, as part of my program, I automatically want to open up the exported dwg file inside a new session of AutoCAD. Sometimes it stays and sometimes it opens and closes quickly. The wrong version of AutoCAD is launched, such as 2022 instead of 2024. If I have AutoCAD already open, and I open another file through file explorer, the AutoCAD application will open a second time to show the new file. Apr 21, 2017 · Hi, ok, my next step would now be to erase 50% of the content, save, close, reopen, watch speed and repeat this until you have found the bad part of the drawing. Note: You can use Ctrl+Tab or Ctrl+F6 to switch between open drawings. This file is useful if you want to load a library of AutoLISP routines to be available every time you start a new drawing (or open an existing drawing). On the command line, type SDI and set the value to 0 (zero). On the command line, type SDI and press Enter. Next, double-click a DWG file in Windows. NET) Jul 25, 2019 · Mornin'! Up until recently, this never happened. > open and then went to Windows Explorer and double clicked on a drawing file, > it would open a NEW session of LDT and keep the other drawing open. If I am understanding correctly, I think Opening a drawing file in AutoCAD takes a long time and the software occasionally freezes. Displays the Startup or the Create New Drawing dialog box. If available in the application, a custom dialog box is displayed. Edit the following registry keys (see Warning below): Click Start and enter regedit Apr 25, 2018 · Startup DWG TrueView 2018 and then exit it. In the Start tab, click Open. Enter new value for Taskbar <0>: Enter 1 to display multiple open drawings as separate items on the Windows taskbar. Convert. The default setting, 0, displays only the name of the current drawing on the Windows taskbar. Use the WBLOCK command to create a new DWG file. Solved by rkmcswain. May 24, 2024 · When launching AutoCAD product or switching between profiles, one or more changes previously made revert to default or to a last-saved state or position. The mouse cursor may Mar 7, 2006 · Open new session of AutoCAD. NET) Create and Open a Drawing (. Open the desired template (or drawing file). Nov 15, 2023 · Solution: In the window, select AutoCAD DWG Launcher. Click OK. Choose Always reassociate DWG files with AutoCAD (recommended). How do I force AutoCAD to open multiple drawings in a single session? Answer . Then pick the AutoCAD Drawing Template (*. Not all the minimum system requirements are fulfilled. To get round this open up LT on it's own, then using the FILE, OPEN menu open up a drawing. When AutoCAD loads a customization file, it searches for an MNL file with a matching file name. Busca trabajos relacionados con Autocad opens new session every drawing o contrata en el mercado de freelancing más grande del mundo con más de 23m de trabajos. Choose New from the Quick Access toolbar to display the Select template dialog box, which opens in the default AutoCAD Template folder. . Separate drawings will not open within the same session of the program. If this works, then exit TrueView and launch and exit AutoCAD Mechanical 2018, and then test double-clicking DWG files again. This is the only drawing it happens to and it's done this to me now every morning for almost a month. Occasionally you will want to check if the Problem: AUTOCAD (LT) is already open. Click on the AutoCAD version you wish to uninstall. 04-18-2024 03:53 AM. This can be achieved by setting the STARTUP (System Variable) to a value of <1>. System. Oct 8, 2023 · To recover the drawing views. Good luck. The original x-ref and the drawing you inserted the x-ref into. Now you can update the model in one drawing and edit paper space in the other. Inventor version is not registered for the corresponding file types. Drag a drawing from File Explorer onto the product shortcut icon. Note: This option is available if you have more than one drawing open Oct 8, 2023 · Click New on the Quick Access Toolbar or enter the QNEW command. Expand 'Template Settings'. Close all instances of AutoCAD. You may also handle (open) the DWG files with " AutoCAD DWG Apr 14, 2019 · In this scenario a new instance of AutoCAD is started when an instance of AutoCAD is already running and a user opens a DWG file from Windows Explorer. This should open just that drawing in a session of autocad. Open New Blank Drawing QuicklyToday we are going to open a new blank drawing file from the opening page. Open AutoCAD. Es gratis registrarse y presentar tus propuestas laborales. That is not the problem. 01-28-2020 03:15 AM. Now, every time I open a new drawing in autocad, the text window opens up as a pop up. Oct 30, 2010 · Open an Explorer window, select Tools --> Folder Options --> File Types tab. See attached image. Now in. Possible scenarios are: AutoCAD is launched instead of AutoCAD LT, or the other way around. > open the drawing you double clicked in the current LDT session. The Open method opens an existing drawing. Jan 11, 2019 · AUTOCAD 2019 always opens in new window. dwg it opens in a new window and open up the programe again. Create new file > Draw detail > X-Ref drawing > Open new file > Insert X-ref > Open in paper space. dvrVSNMW. I have tried almost everything. User profile corruption. exe is set a new session of AutoCAD (LT) will be started with every double-click. STARTMODE: Mar 21, 2024 · When double-clicking a DWG file from a file explorer, the wrong AutoCAD-based program launches. Restart AutoCAD. Thank you for contacting us. There is also a Close method on the Documents collection that closes all the drawings open in the AutoCAD session. If I have opened a drawing in DWGviewer and then double click a drawing in Windows to open it, it will open it in DWGviewer. Separate instances of AutoCAD can then positioned side by side. Sometimes, the desired file may also open alongside the blank one. Being a novice at this setup, not sure if/how possible. thanks in advance for your help. Prior to clicking, hovering over items may show highlight feedback which stops once the program is frozen. Now check 'Use DDE' if you want to open DWGs in a single session or uncheck it for multiple sessions. Drag and drop the drawing file to your AutoCAD desktop icon. The Add method creates a new drawing file based on a drawing template and adds that drawing to the DocumentCollectionExtension. I tried to do the same with Plant 3D and it kind o' works Dec 11, 2019 · Just got a second monitor for the purpose of having two tabs open at the same time to work on two drawings with only one session of ACAD2020 opened using windows 10. 3. lsp file is intended to be associated with each document (or drawing) initialization. Import CAD (STP, IGES) files. Hi all, Our company has a manual procedure where when we issue drawings, we bind. Select Always use this app to open . May 7, 2024 · Close all instances of all AutoCAD applications. They should both come up in the same instance of DWG TrueView. Opening up 4 separate drawings will result in 4 new drawings I have to delete. xrefs, purge the drawing and then place in an issued folder. Enter EXPORTLAYOUT (command) and choose a location to save the output file. the remedy given to me did indeed work. This will allow to position the two AutoCAD instances side by side. So for now, I will mark this thread as "Solved. If you are new to AutoCAD and are looking for a book to help expand you Let me know if you want more info on this. Environment: Windows 10. Apr 23, 2024 · When opening an Inventor file from the Vault, Inventor opens a new session instead of using the existing Inventor instance. dwt or drawing templates. The program window is black or blank while the file opens, making it look like the drawing content is missing. (not an Autodesk consultant) Report. Use the SAVEAS command and bring up the Save Drawing As dialog box. Another drawing is being openend from Windows explorer (double-click) but this starts a new AutoCAD (LT) session and does not add the drawing to the existing session. I have a rather large drawing and every time I open it, I'm forced to save it under a new name because the system claims that it is currently in use. /b c:\dumpdocs. Double-click a drawing in File Explorer. I can get Vanilla AutoCAD to open up, but then it cant find my drawing. NET) To create a new drawing or open an existing drawing, use the methods of the DocumentCollectionExtension object. 2. Run the OVERKILL command. I want each drawing to open in the same session, this prevents a million tabs in the taskbar and all my macros from having to reload every time. U are talking about the taskbar. That works fine; but now when I open from explorer, I get a new session of AutoCAD for every drawing I open. in reply to: dvrVSNMW. Assign the correct program version to the Inventor file types (IAM, IPT, IDW, IPN) with following steps: Get a file of the corresponding file type Dec 3, 2008 · Re: Open Drawing in New Window. env file just now, saw no mention of . Mar 15, 2024 · Attempts to open multiple drawings within the same AutoCAD session fail, and the user is prompted to save the current drawing, prior to opening or creating any other drawing. NET) Control the AutoCAD Environment (. Aug 7, 2023 · Start AutoCAD. Apr 4, 2023 · Press WINDOWS-R on the keyboard to bring up the Run window, enter REGEDIT and click OK. Search for jobs related to Autocad opens new session every drawing or hire on the world's largest freelancing marketplace with 23m+ jobs. Note: If the dialogue does not come up, close and restart AutoCAD. dwg file. Use the RECOVER or RECOVERALL command to open/repair the drawing. Create and Open a Drawing (. One or more of the following may also occur:AutoCAD is frozen while it loads the drawing but recovers when the file opens. Software corruption. Re-associate DWG files with the AutoCAD DWG Launcher (see DWG file type associativity in Windows ). If it doesn't click the Advanced button, select the open action & click Edit. Oct 17, 2023 · AutoCAD offers a system variable named SDI (Single Document Interface). lsp using Windows Notepad or other plain text editor. Launch the program again (do not double-click a DWG file) and start a new drawing. Select the Look in: list at the top of the dialog box, and open the Chapter 2 folder in the May 18, 2022 · How to set your template file as one of the default options when you open a new drawing in AutoCAD. An AutoCAD toolset (like AutoCAD Architecture, Mechanical, or Civil 3D) is launched instead of AutoCAD or the other way around. The SDI (Single Document Interface) system variable is set to 1. Imperial Oct 8, 2023 · Ask the Assistant. This may occur with: Settings in Options. When double-clicking a DWG file in Windows, the drawing opens in AutoCAD. This is very annoying as we need to work on multiple files at a time and opening new session everytime, reduces system performance and decreases efficiency. Welcome to the Autodesk Community! It seems that JJ's suggestion to check the SDI variable and ensure it's set to 0 could indeed resolve your problem. Mar 8, 2006 · Hi all, Our company has a manual procedure where when we issue drawings, we bind xrefs, purge the drawing and then place in an issued folder. For other operating systems it might differ slightly. Aug 16, 2012 · I've always found that method of opening drawings buggy especially on machines with more than one version AutoCAD. After this new drawing is created then my target drawing opens next. Generally the STARTUP values correspond to the following: Starts a drawing without defined settings. The value of the SDI variable determines Oct 22, 2017 · Hi, I'm using AutoCAD 2016 on Windows 10. Use the Convert DWG tool in DWG TrueView to convert the drawing to a Jul 23, 2009 · Currently in AutoCAD 2008, evertime I browse my folders and dbl click a dwg - AutoCAD opens that drawing in a new window. Right-click a file tab, and choose Open. Windows file association is set to a different software. The drawing has been damaged or is corrupted. I need to open a lot of drawings quickly throughout the day, so the file>open Nov 17, 2011 · When I click on this drawing a *new* drawing is automatically created first called "drawing1. MORE VIDEOS FOR INTERIOR DESIGNHow to make a Title Block In this tutorial, I show you two ways to start a new drawing, choose a template, and how to rename and save your drawing correctly. The procedure described here is relative to Windows 10. Open File Explorer and navigate to the drawing. Elevate or de-elevate permissions of AutoCAD and the Aug 5, 2014 · Apparently, the Launcher controls the MDI/SDI option, the Autocad application its self is blind. dwg files to open with AutoCAD DWG Launcher. has more than one layout, the user has to manually saveas, delete unwanted. Drag and drop the DWG into the drawing window. I just downloaded AutoCAD 2024 yesterday, and now I'm running into something I've never seen before when opening files. I configured AutoCAD to startup and not to create a new drawing with any template (with the command STARTUP > option 2, in the command line). How to open many AutoCAD Drawings in one instance ? When you open many AutoCAD files and you press ( ALT + TAB ) you get them all. Open the drawing in AutoCAD. May 31, 2024 · A new Instance of Autodesk Inventor opens when, despite one active session was already running: Double-clicking on Inventor file (IPT, IAM, IDW, DWG, IPN) in Windows Explorer or Vault Client. al jk ob et bl iz fs qt ke ab