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  • Are bit operations quick?

    - by flashnik
    I'm dealing with a problem which needs to work with a lot of data. Currently its' values are represented as unsigned int. I know that real values do not exceed some limit, say 1000. That means that I can use unsigned short to store it. One profit is that it'll use less space. Do I have to pay for it by loosing in performance? Another assumption. I decided to store data as short but all calling functions use int, so I need to convert between these datatypes when storing/extracting values. Wiil the performance lost be dramatic? Third assumption. Due to great wish to econom memory I decided to use not short but just 10 bits packed into array of unsigned int. What will happen in this case comparing with previous ones?

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  • c - difficulties with bit operations

    - by hatorade
    I'm debugging a program with GDB. unsigned int example = ~0; gives me: (gdb) x/4bt example 0xffd99788: 10101000 10010111 11011001 11111111 why is this not all 1's? i defined it as ~0... then the next line of code is: example>>=(31); and GDB gives me this when I try to examine the memory at bits: (gdb) x/4bt example 0xffffffff: Cannot access memory at address 0xffffffff what is going on???

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  • Do bit operations cause programs to run slower?

    - by flashnik
    I'm dealing with a problem which needs to work with a lot of data. Currently its values are represented as an unsigned int. I know that real values do not exceed a limit of 1000. Questions I can use unsigned short to store it. An upside to this is that it'll use less storage space to store the value. Will performance suffer? If I decided to store data as short but all the calling functions use int, it's recognized that I need to convert between these datatypes when storing or extracting values. Will performance suffer? Will the loss in performance be dramatic? If I decided to not use short but just 10 bits packed into an array of unsigned int. What will happen in this case comparing with previous ones?

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  • bit ordering and endianess

    - by Neeraj
    I am reading a file byte-by-byte. Say for example i have this byte: 0x41 (0100 0001) represented in hex. Now, I want the first three bits of this byte, i.e (010). I can use bitwise logic to extract the first three bits, but my question is will the first three bits be independent of endianess of the machine.(i.e they can't be 001)? Thanks,

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  • C Population Count of unsigned 64-bit integer with a maximum value of 15

    - by BitTwiddler1011
    I use a population count (hamming weight) function intensively in a windows c application and have to optimize it as much as possible in order to boost performance. More than half the cases where I use the function I only need to know the value to a maximum of 15. The software will run on a wide range of processors, both old and new. I already make use of the POPCNT instruction when Intel's SSE4.2 or AMD's SSE4a is present, but would like to optimize the software implementation (used as a fall back if no SSE4 is present) as much as possible. Currently I have the following software implementation of the function: inline int population_count64(unsigned __int64 w) { w -= (w 1) & 0x5555555555555555ULL; w = (w & 0x3333333333333333ULL) + ((w 2) & 0x3333333333333333ULL); w = (w + (w 4)) & 0x0f0f0f0f0f0f0f0fULL; return int(w * 0x0101010101010101ULL) 56; } So to summarize: (1) I would like to know if it is possible to optimize this for the case when I only want to know the value to a maximum of 15. (2) Is there a faster software implementation (for both Intel and AMD CPU's) than the function above?

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  • OWB 11gR2 - Windows and Linux 64-bit clients available

    - by David Allan
    In addition to the integrated release of OWB in the 11.2.0.3 Oracle database distribution, the following 64-bit standalone clients are now available for download from Oracle Support. OWB 11.2.0.3 Standalone client for Windows 64-bit - 13365470 OWB 11.2.0.3 Standalone client for Linux X86 64-bit - 13366327 This is in addition to the previously released 32-bit client on Windows. OWB 11.2.0.3 Standalone client for Windows 32-bit - 13365457 The support document Major OWB 11.2.0.3 New Features Summary has details for OWB 11.2.0.3 which include the following. Exadata v2 and oracle Database 11gR2 support capabilities; Support for Oracle Database 11gR2 and Exadata compression types Even more partitioning: Range-Range, Composite Hash/List, System, Reference Transparent Data Encryption support Data Guard support/certification Compiled PL/SQL code generation Capabilities to support data warehouse ETL best practices; Read and write Oracle Data Pump files with external tables External table preprocessor Partition specific DML Bulk data movement code templates: Oracle, IBM DB2, Microsoft SQL Server to Oracle Integration with Fusion Middleware capabilities; Support OWB's Control Center Agent on WLS Lots of interesting capabilities in 11.2.0.3 and the availability of the 64-bit client I'm sure is welcome news for many!

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  • SQL SERVER – Fix: Error: 8117: Operand data type bit is invalid for sum operator

    - by pinaldave
    Here is the very interesting error I received from a reader. He has very interesting question. He attempted to use BIT filed in the SUM aggregation function and he got following error. He went ahead with various different datatype (i.e. INT, TINYINT etc) and he was able to do the SUM but with BIT he faced the problem. Error Received: Msg 8117, Level 16, State 1, Line 1 Operand data type bit is invalid for sum operator. Reproduction of the error: Set up the environment USE tempdb GO -- Preparing Sample Data CREATE TABLE TestTable (ID INT, Flag BIT) GO INSERT INTO TestTable (ID, Flag) SELECT 1, 0 UNION ALL SELECT 2, 1 UNION ALL SELECT 3, 0 UNION ALL SELECT 4, 1 GO SELECT * FROM TestTable GO Following script will work fine: -- This will work fine SELECT SUM(ID) FROM TestTable GO However following generate error: -- This will generate error SELECT SUM(Flag) FROM TestTable GO The workaround is to convert or cast the BIT to INT: -- Workaround of error SELECT SUM(CONVERT(INT, Flag)) FROM TestTable GO Clean up the setup -- Clean up DROP TABLE TestTable GO Workaround: As mentioned in above script the workaround is to covert the bit datatype to another friendly data types like INT, TINYINT etc. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • how can I get 32-bit program to run on 64-bit Ubuntu?

    - by Carol
    Sorry to be asking this, but I have read quite a few posts and articles a lot of places wrt the issue I am having, to no avail. I am trying to get a Second Life Viewer (Firestorm) to run, and just keep getting the '64-bit error message' it throws. I have installed every 32-lib I can find, still doesn't work. I think I am surely missing some setting somewhere, or running Firestorm from the wrong place, or something, but I have no idea what. FWIW, Firestorm loads but doesn't behave right in the 32-bit version, either. I have actually tried several linux distros, 32 and 64-bit. Mint 32-bit runs it straight off, and Mint 64-bit throws the '64-bit error'. openSUSE, any version, won't run it at all. Oh, and all the other SL viewers I have tried behave the same way. I am beginning to wonder if my set-up just doesn't like linux. Here is my system info: CPU: Intel(R) Core(TM) i5 CPU 750 @ 2.67GHz (2661 MHz) Memory: 4026 MB OS Version: Linux 3.2.0-29-generic-pae #46-Ubuntu SMP Fri Jul 27 17:25:43 UTC 2012 i686 Graphics Card Vendor: ATI Technologies Inc. Graphics Card: ATI Radeon HD 5700 Series I appreciate any help anyone can give me! Thanks so much! Carol :)

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  • Running 32 bit assembly code on a 64 bit Linux & 64 bit Processor : Expalin the anomaly.

    - by claws
    Hello, I'm in an interesting problem.I forgot I'm using 64bit machine & OS and wrote a 32 bit assembly code. I don't know how to write 64 bit code. This is the x86 32-bit assembly code for Gnu Assembler (AT&T syntax) on Linux. #include <asm/unistd.h> #include <syscall.h> #define STDOUT 1 .data hellostr: .ascii "hello wolrd\n"; helloend: .text .globl _start _start: movl $(SYS_write) , %eax //ssize_t write(int fd, const void *buf, size_t count); movl $(STDOUT) , %ebx movl $hellostr , %ecx movl $(helloend-hellostr) , %edx int $0x80 movl $(SYS_exit), %eax //void _exit(int status); xorl %ebx, %ebx int $0x80 ret Now, This code should run fine on a 32bit processor & 32 bit OS right? As we know 64 bit processors are backward compatible with 32 bit processors. So, that also wouldn't be a problem. The problem arises because of differences in system calls & call mechanism in 64-bit OS & 32-bit OS. I don't know why but they changed the system call numbers between 32-bit linux & 64-bit linux. asm/unistd_32.h defines: #define __NR_write 4 #define __NR_exit 1 asm/unistd_64.h defines: #define __NR_write 1 #define __NR_exit 60 Anyway using Macros instead of direct numbers is paid off. Its ensuring correct system call numbers. when I assemble & link & run the program. Its not printing helloworld. In gdb its showing: Program exited with code 01. I don't know how to debug in gdb. using tutorial I tried to debug it and execute instruction by instruction checking registers at each step. its always showing me "program exited with 01". It would be great if some on could show me how to debug this. (gdb) break _start Note: breakpoint -10 also set at pc 0x4000b0. Breakpoint 8 at 0x4000b0 (gdb) start Function "main" not defined. Make breakpoint pending on future shared library load? (y or [n]) y Temporary breakpoint 9 (main) pending. Starting program: /home/claws/helloworld Program exited with code 01. (gdb) info breakpoints Num Type Disp Enb Address What 8 breakpoint keep y 0x00000000004000b0 <_start> 9 breakpoint del y <PENDING> main I tried running strace. This is its output: execve("./helloworld", ["./helloworld"], [/* 39 vars */]) = 0 write(0, NULL, 12 <unfinished ... exit status 1> Explain the parameters of write(0, NULL, 12) system call in the output of strace? What exactly is happening? I want to know the reason why exactly its exiting with exitstatus=1? Can some one please show me how to debug this program using gdb? Why did they change the system call numbers? Change this program appropriately so that it can run correctly on this machine.

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  • Can't control connection bit rate using iwconfig with Atheros TL-WN821N (AR7010)

    - by Paul H
    I'm trying to reduce the connection bit rate on my Atheros TP-Link TL-WN821N v3 usb wifi adapter due to frequent instability issues (reported connection speed goes down to 1Mb/s and I have to physically reconnect the adapter to regain a connection). I know this is a common problem with this device, and I have tried everything I can think of to fix it, including using drivers from linux-backports; compiling and installing a custom firmware (following instructions on https://wiki.debian.org/ath9k_htc#fw-free) and (as a last resort) using ndiswrapper. When using ndiswrapper, the wifi adapter is stable and operates in g mode at 54Mb/s (whilst when using the default ath9k_htc module, the adapter connects in n mode and the bit rate fluctuates constantly). Unfortunately, with this setup I have to run my processor using only one core, since using SMP with ndiswrapper causes a kernel oops on my system. So I want to lock my bit rate to 54Mb/s (or less, if need be) for connection stability, using the ath9k_htc module. I've tried 'sudo iwconfig wlan0 rate 54M'; the command runs with no error but when I check the bit rate with 'sudo iwlist wlan0 bitrate' the command returns: wlan0 unknown bit-rate information. Current Bit Rate:78 Mb/s Any ideas? Here's some info (hopefully relevant) on my setup: Xubuntu (12.04.3) 64bit (kernel 3.2.0-55.85-generic) using Network Manager. My Router is from Virgin Media, the VMDG480. lshw -C network : *-network description: Wireless interface physical id: 1 bus info: usb@1:4 logical name: wlan0 serial: 74:ea:3a:8f:16:b6 capabilities: ethernet physical wireless configuration: broadcast=yes driver=ath9k_htc driverversion=3.2.0-55 firmware=1.3 ip=192.168.0.9 link=yes multicast=yes wireless=IEEE 802.11bgn lsusb -v: Bus 001 Device 003: ID 0cf3:7015 Atheros Communications, Inc. TP-Link TL-WN821N v3 802.11n [Atheros AR7010+AR9287] Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 255 Vendor Specific Class bDeviceSubClass 255 Vendor Specific Subclass bDeviceProtocol 255 Vendor Specific Protocol bMaxPacketSize0 64 idVendor 0x0cf3 Atheros Communications, Inc. idProduct 0x7015 TP-Link TL-WN821N v3 802.11n [Atheros AR7010+AR9287] bcdDevice 2.02 iManufacturer 16 ATHEROS iProduct 32 UB95 iSerial 48 12345 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 60 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0x80 (Bus Powered) MaxPower 500mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 6 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 0 bInterfaceProtocol 0 iInterface 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x01 EP 1 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x82 EP 2 IN bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x83 EP 3 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0040 1x 64 bytes bInterval 1 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x04 EP 4 OUT bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0040 1x 64 bytes bInterval 1 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x05 EP 5 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x06 EP 6 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0 Device Qualifier (for other device speed): bLength 10 bDescriptorType 6 bcdUSB 2.00 bDeviceClass 255 Vendor Specific Class bDeviceSubClass 255 Vendor Specific Subclass bDeviceProtocol 255 Vendor Specific Protocol bMaxPacketSize0 64 bNumConfigurations 1 Device Status: 0x0000 (Bus Powered) iwlist wlan0 scanning: wlan0 Scan completed : Cell 01 - Address: C4:3D:C7:3A:1F:5D Channel:1 Frequency:2.412 GHz (Channel 1) Quality=37/70 Signal level=-73 dBm Encryption key:on ESSID:"my essid" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s 24 Mb/s; 36 Mb/s; 54 Mb/s Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s Mode:Master Extra:tsf=00000070cca77186 Extra: Last beacon: 5588ms ago IE: Unknown: 0007756E69636F726E IE: Unknown: 010882848B962430486C IE: Unknown: 030101 IE: Unknown: 2A0100 IE: Unknown: 2F0100 IE: IEEE 802.11i/WPA2 Version 1 Group Cipher : TKIP Pairwise Ciphers (2) : CCMP TKIP Authentication Suites (1) : PSK IE: Unknown: 32040C121860 IE: Unknown: 2D1AFC181BFFFF000000000000000000000000000000000000000000 IE: Unknown: 3D1601080400000000000000000000000000000000000000 IE: Unknown: DD7E0050F204104A0001101044000102103B00010310470010F99C335D7BAC57FB00137DFA79600220102100074E657467656172102300074E6574676561721024000631323334353610420007303030303030311054000800060050F20400011011000743473331303144100800022008103C0001011049000600372A000120 IE: Unknown: DD090010180203F02C0000 IE: WPA Version 1 Group Cipher : TKIP Pairwise Ciphers (2) : CCMP TKIP Authentication Suites (1) : PSK IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00 iwconfig: lo no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"my essid" Mode:Managed Frequency:2.412 GHz Access Point: C4:3D:C7:3A:1F:5D Bit Rate=78 Mb/s Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=36/70 Signal level=-74 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0,

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  • What are the correct set of DLLs and placement for SSL support in mIRC on 64 bit Windows?

    - by honkbish
    I am using mIRC 6.35 on a fresh install of Windows 7 64-bit. No matter what versions of the OpenSSL DLLs I use, nor where I place them, I cannot get mIRC to work with SSL; I get the "ssl not supported" error. The recommended DLLs on mIRC's help page (/ssl.html on the mIRC site) do not work no matter if I put them in the mIRC Program Files folder or anywhere else. Same with the DLLs from http://www.slproweb.com/products/Win32OpenSSL.html which also require Visual C++ runtimes. I am unsure if I need the 32bit DLLs (because mIRC itself is 32 bit), or the 64-bit DLLs, nor where to correctly place them. (Perhaps I currently have a case of incorrect DLLs in a path I am not aware of overriding the other placements...) Does ANYONE have any tips for 'debugging' this, or do they themselves have it working? Thanks in advance!

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  • How do you setup 64-bit PHP5 with APC?

    - by amvx
    I followed this # script on my webhost's wiki to setup a custom install of PHP5, but now theyre telling me they need to move my account to a 64-bit server, and I have no idea how to set this up. APC needs the PHP5 installation to use cgi/fastcgi. I Dunno how that applies to 64-bit or what other considerations need to be made. Does anyone have any idea how to do this, or by least changing the #script to compile using the 64-bit PHP. I'm learning so much from this site, thanks for your help.

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  • Copy all installed programs & files in a hard disk (which has 32 bit Windows 7) and clone/transfer it to another computer which has 64 bit Windows 7

    - by galacticninja
    I recently got a new PC which has a 64-bit Windows 7 installed. The current PC that I am using has a 32-bit Windows 7 installed. I would like to know if there is a software that can copy all my installed programs and files in the hard disk with the 32-bit Windows 7 PC and transfer it to the newer PC's hard disk which has a 64 bit version of Windows 7. This is essentially like "cloning" a hard disk but I would like to use a 64-bit OS in the target drive, instead of also using the 32-bit OS of the source drive. I would like to do this I can avoid reinstalling and reconfiguring my installed programs and files again on the new PC. If possible, I would like the new PC to work as it was in my previous PC, with the installed programs, configuration and files intact except that the OS is now 64-bit and the hard disk has a larger capacity. I have heard of programs that can clone a hard disk, but my concern is that the 32-bit Windows 7 OS will also be cloned to the new 64-bit PC. If it is not possible to transfer my installed programs and settings like the way I described, are there software that can make it easier to migrate my installed programs, their configurations and my files from a 32-bit Windows 7 PC to a 64-bit Windows 7 PC? Details: I have a SATA to USB connector/adapter to copy files in the current hard disk to the newer one. The two PCs are connected through LAN, so I can also transfer files through LAN. Both PCs only have one hard disk.

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  • Efficient bitshifting an array of int?

    - by nn
    Hi, To be on the same page, let's assume sizeof(int)=4 and sizeof(long)=8. Given an array of integers, what would be an efficient method to bitshift the array to either the left or right? I am contemplating an auxiliary variable such as a long, that will compute the bitshift for the first pair of elements (index 0 and 1) and set the first element (0). Continuing in this fashion the bitshift for elements (index 1 and 2) will be computer, and then index 1 will be set. I think this is actually a fairly efficient method, but there are drawbacks. I cannot bitshift greater than 32 bits. I think using multiple auxiliary variables would work, but I'm envisioning recursion somewhere along the line.

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  • Getting value of LSB from Hex (C code)

    - by Rjff
    Hi - first post here :) I've got a code like this in C: unsigned char const data[ ] = {0x0a, 0x1d, 0xf0, 0x07}; I need to extract it such that the final value is: 0xa1df7 I have only been able to extract and get it working if the hex values that have at least 1 zero: unsigned char const data[ ] = {0x0a, 0xd0, 0xf0, 0x07}; using the code below: for(int i = 0; i < SIZE; ++i) { tmp = data[i]; if ( (data[i] <= 0x0F) && (((data[i] & 0x0F) == 0) || (data[i] & 0xF0) == 0)) // one of the hex is zero { tmp = ((tmp << 4) >> 4) << N[i]; std::cout << "foo: " << std::hex << tmp << ":" << std::endl; } else if ((data[i] >= 0x0F) && (((data[i] & 0x0F) == 0) || (data[i] & 0xF0) == 0) ) { tmp = (tmp >> 4) << N[i]; std::cout << "bar: " << std::hex << tmp << ":" << std::endl; } else { std::cout << "result: " << std::hex << result << ":" << std::endl; std::cout << "tmp << 8: " << std::hex << (tmp << 8)<< ":" << std::endl; result = result | (tmp << 8); std::cout << "result |= (tmp << 8): " << std::hex << result << ":" << std::endl; } result |= tmp; std::cout << "boo: " << std::hex << result << ":" << std::endl; } It seems the last else {...} block is troublesome for me. Any ideas? Thanks!

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  • C++ shifting bits

    - by Bobby
    I am new to shifting bits, but I am trying to debug the following snippet: if (!(strcmp(arr[i].GetValType(), "f64"))) { dem_content_buff[BytFldPos] = tmp_data; dem_content_buff[BytFldPos + 1] = tmp_data >> 8; dem_content_buff[BytFldPos + 2] = tmp_data >> 16; dem_content_buff[BytFldPos + 3] = tmp_data >> 24; dem_content_buff[BytFldPos + 4] = tmp_data >> 32; dem_content_buff[BytFldPos + 5] = tmp_data >> 40; dem_content_buff[BytFldPos + 6] = tmp_data >> 48; dem_content_buff[BytFldPos + 7] = tmp_data >> 56; } I am getting a warning saying the lines with "32" to "56" have a shift count that is too large. The "f64" in the predicate just means that the data should be 64bit data. How should this be done?

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  • 64-bit TortoiseSVN on Windows 7 says "file or directory is corrupted and unreadable" then runs chkds

    - by David Alpert
    I'm using 64-bit TortoiseSVN on a 64-bit Windows 7 Professional. Every so often a checkout or update will fail with an error message like the following: Error: Can't move Error: '[...]\\.svn\tmp\entries' Error: to Error: '[...]\\.svn\entries': Error: The file or directory is corrupted and unreadable. then CHKDSK runs after reboot, which makes me nervous. Does anyone know why this might be happening or how I can avoid it?

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  • How can I find out if a given program is 64 or 32 bit version?

    - by maaartinus
    How can I find out if a given program is 64 or 32 bit version? I can't to do it by simply looking at where it's installed, since some programs need no installer and may be put anywhere. Here, no process explorer will help me, since the application refuses to start. Reason why I need it: My new eclipse installation fails to load "jvm.dll" just like here. I'd bet I'm using 64-bit versions of both eclipse and JVM, but I'm slowly getting unsure....

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  • How can I run a (16-bit) .COM executable that has been renamed to .COS?

    - by max16bit
    I'm trying to run a couple of 16-bit legacy DOS programs from a standard windows XP dos prompt. The problem is that the file extensions have been renamed from .COM to .COS and they are stored on read-only media and I can't copy them (special environment). Any tips on how to invoke such files despite the weird extension? If they had been 32-bit EXEs, it wouldn't have been an issue running them even without their proper extensions, but with these COM files, I'm unable to find a way to run them.

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