offline blog editor

Tired of editing your blog online with the small editting window of google's blogger and other blog providers.I have a solution.dowload the offline blog editor w.bloggar and install it on your pc and write your post and post it.

click here to download the w.bloggar

   Main Feautures

 

• post and Publish on most blogs/cms tools and services


• Edit Posts and Templates


• Save Posts locally for further publishing


• Import Text files


• Add links and images


• Format text font and alignment


• Multiple accounts and blogs


• Post preview


• Colorized HTML code


• HTML tags menu


• Find/Replace option


• Post to many blogs


• Title and Category Fields


• Spell Checking


• File and Image Upload


• Custom Tags Menu


• Toolbar Icons Skin


• Supports Windows XP


• Support to the advanced MovableType options New!


• Add Account Wizard New!


• Support to Multiple Categories New!


• Option to XHTML compliance New!


• Import and Export Settings New!


• Ping to Weblogs.Com, blo.gs, Technorati and ping-o-matic New!


• No Spyware!


• No Nag Screens!

TRICK TO TEST WHETHER YOUR ANTIVIRUS IS PROTECTING YOU OR NOT!!

Open notepad and paste this:


X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*


Save it as eicar.com. The Anti-Virus should stop you (if it does that means its working).

Don't worry about it. European Institute for Computer Anti-virus Research (EICAR) have got people to program Anti-Virus to recognise this as a threat (even tough it's completely harmless)...

DDR3 memory chips

With 64-bit operating systems finally becoming more mainstream, the demand for more RAM appears to be mounting. At least that is what Samsung hopes, with the company recently announcing new two-gigabit (256MB) DDR3 chips that will enable memory modules with up to 16GB capacity. 
            Using a new 50 nanometer manufacturing process, these DDR3 chips are twice as dense as before and boast a power consumption drop of 40 percent over one-gigabit modules. Samsung claims that the new chips are capable of faster speeds too, quoting a data rate of 1.3Gb/sec at 1.5V or 1.35V for a new 2Gb chip, compared with 800Mb/sec for a 1Gb dual-die package. 
            The company plans to begin mass production later this year and expects the new technology to become their primary DRAM process technology next year.

DDR3 SDRAM

In electronic engineering, DDR3 SDRAM or double-data-rate three synchronous dynamic random access memory is a random access memory technology used for high speed storage of the working data of a computer or other digital electronic device.

DDR3 is part of the SDRAM family of technologies and is one of the many DRAM (dynamic random access memory) implementations. DDR3 SDRAM is an improvement over its predecessor, DDR2 SDRAM.

The primary benefit of DDR3 is the ability to transfer I/O data at eight times the speed of the memory cells it contains, thus enabling faster bus speeds and higher peak throughput than earlier memory technologies. However, there is no corresponding reduction in latency, which is therefore proportionally higher. In addition, the DDR3 standard allows for chip capacities of 512 megabits to 8 gigabits, effectively enabling a maximum memory module size of 16 gigabytes.

  

 Contents 

1 Overview

1.1 Latencies

2 Extensions

3 Specification standards

3.1 Chips and modules

4 References

5 See also

6 External links

Overview

DDR3 memory promises a power consumption reduction of 30% compared to current commercial DDR2 modules due to DDR3's 1.5 V supply voltage, compared to DDR2's 1.8 V or DDR's 2.5 V. The 1.5 V supply voltage works well with the 90 nanometer fabrication technology used for most DDR3 chips. Some manufacturers further propose using "dual-gate" transistors to reduce leakage of current.[1]

According to JEDEC[2] the maximum recommended voltage is 1.575 volts and should be considered the absolute maximum when memory stability is the foremost consideration, such as in servers or other mission critical devices. In addition, JEDEC states that memory modules must withstand up to 1.975 volts before incurring permanent damage, although they are not required to function correctly at that level.

The main benefit of DDR3 comes from the higher bandwidth made possible by DDR3's 8 bit deep prefetch buffer, in contrast to DDR2's 4 bit prefetch buffer or DDR's 2 bit buffer.

DDR3 modules can transfer data at the effective clock rate of 800–1600 MHz using both rising and falling edges of a 400–800 MHz I/O clock. In comparison, DDR2's current range of effective data transfer rate is 400–800 MHz using a 200–400 MHz I/O clock, and DDR's range is 200–400 MHz based on a 100–200 MHz I/O clock. To date, the graphics card market has been the driver of such bandwidth requirements, where fast data transfer between framebuffers is required.

DDR3 prototypes were announced in early 2005. Products in the form of motherboards are appearing on the market as of mid-2007 based on Intel's P35 "Bearlake" chipset and memory DIMMs at speeds up to DDR3-1600 (PC3-12800).[4] AMD's roadmap indicates their own adoption of DDR3 in 2008.

DDR3 DIMMs have 240 pins, the same number as DDR2, and are the same size, but are electrically incompatible and have a different key notch location.[5] DDR3 SO-DIMMs have 204 pins.

Latencies

The typical latency for a DDR2 JEDEC standard was 5-5-5-15. The JEDEC standard latencies for the newer DDR3 memory are 7-7-7-15. One thing to be aware of, however, is that while these are the standards, manufacturing processes tend to improve with time. Eventually, DDR3 modules will likely be able to run at lower latencies than the JEDEC specifications. It is possible to find DDR2 memory that is faster than the standard 5-5-5-15 speeds, but it will take time for DDR3 to fall below the JEDEC latencies.

DDR3 latencies are numerically higher because the clock cycles by which they are measured are shorter; the actual time interval is generally equal to or lower than DDR2 latencies.

GDDR3 memory, having a similar name but being from an entirely dissimilar technology, has been in use for high-end graphic cards by companies such as NVIDIA and ATI Technologies. GDDR3 has sometimes been incorrectly referred to as "DDR3".

Extensions

Intel Corporation officially introduced the eXtended Memory Profile (XMP) Specification on March 23rd, 2007 to enable enthusiast performance extensions to the traditional JEDEC SPD specifications for DDR3 SDRAM.

Specification standards

Chips and modules

Standard nameMemory clockCycle timeI/O Bus clockData transfers per secondModule namePeak transfer rateDDR3-800100 MHz10 ns400 MHz800 MillionPC3-64006400 MB/sDDR3-1066133 MHz7.5 ns533 MHz1066 MillionPC3-85008533 MB/sDDR3-1333166 MHz6 ns667 MHz1333 MillionPC3-1060010667 MB/s[1]DDR3-1600200 MHz5 ns800 MHz1600 MillionPC3-1280012800 MB/s

Features

DDR3 SDRAM Components:

Introduction of asynchronous RESET pin

Support of system level flight time compensation

On-DIMM mirror friendly DRAM pin out

Introduction of CWL (CAS Write Latency) per speed bin

On-die I/O calibration engine

READ and WRITE calibration

DDR3 Modules:

Fly-by command/address/control bus with on-DIMM termination

High precision calibration resistors

Are not backwards compatible-wrongly inserting a DDR3 module into a DDR2 socket can damage the DIMM and/or the motherboard

Advantages compared to DDR2

Higher bandwidth performance, effectively up to 1600 MHz

Higher performance at low power (longer battery life in laptops)

Enhanced low power features

Improved thermal design (cooler)

Disadvantages compared to DDR2

Commonly higher CAS latency

Currently (as of 2008) costs much more than equivalent DDR2 memory

10 things you don't know about nokia

1) The ringtone "Nokia tune" is actually based on a 19th century guitar work named "Gran Vals" by Spanish musician Francisco Tárrega. The Nokia Tune was originally named "Grande Valse" on Nokia phones but was changed to "Nokia Tune" around 1998 when it became so well known that people referred to it as the "Nokia Tune."

2) The world's first commercial GSM call was made in 1991 in Helsinki over a Nokia-supplied network, by Prime Minister of Finland Harri Holkeri, using a Nokia phone.

3) Nokia is currently the world's largest digital camera manufacturer, as the sales of its camera-equipped mobile phones have exceeded those of any conventional camera manufacturer.

4) The "Special" tone available to users of Nokia phones when receiving SMS (text messages) is actually Morse code for "SMS". Similarly, the "Ascending" SMS tone is Morse code for "Connecting People," Nokia's slogan. The "Standard" SMS tone is Morse code for "M" (Message).

5) The Nokia corporate font (typeface) is the AgfaMonotype Nokia Sans font, originally designed by Eric Spiekermann. Its mobile phone User's Guides Nokia mostly used the Agfa Rotis Sans font.

6) In Asia, the digit 4 never appears in any Nokia handset model number, because 4 is considered unlucky in many parts of Southeast/East Asia.

7) Nokia was listed as the 20th most admirable company worldwide in Fortune's list of 2006 (1st in network communications, 4th non-US company).

8. Unlike other modern day handsets, Nokia phones do not automatically start the call timer when the call is connected, but start it when the call is initiated. (Except for Series 60 based handsets like the Nokia 6600)

9) Nokia is sometimes called aikon (Nokia backwards) by non-Nokia mobile phone users and by mobile software developers, because "aikon" is used in various SDK software packages, including Nokia's own Symbian S60 SDK.

10) The name of the town of Nokia originated from the river which flowed through the town. The river itself, Nokianvirta, was named after the old Finnish word originally meaning sable, later pine marten. A species of this small, black-furred predatory animal was once found in the region, but it is now extinct.

writing the linux device driver

Does the idea of writing a Linux device driver sound difficult? If you have some basic programming experience, the task issimpler than you think. Get started with this quick primer ondevice driver programming 

What do I need to know about writing drivers? 
Basic knowledge of kernel compilation, a good deal of programmingexperience in C under Linux and lastly, the right techniques of datastructures, like linked list is essential along with their data types. 
The first thing a programmer must know before attempting to write adriver, is to know how the Linux kernel source compiles, paying attentionto the compilation process (the gcc compiler flags).

Choosing the device type 

a) Block drivers 
A block device is something that can host a filesystem such as a disk. Ablock device can only be accessed as multiples of a block, where a blockis usually one kilobyte of data . 
b) Character drivers 
A character device is one that can be accessed like a file, and a chardriver is in charge of implementing this behaviour. This driver implementsthe open, close, read and write system calls. The console and parallelports are examples of char devices.
Device drivers in Linux are known as modules and can be loaded dynamicallyinto the kernel using the insmod command.A single module can be compiled alone, and also can be linked to thekernel (here, care has to be taken on the type of driver). 

eg: A simple module 
#define MODULE#include 
int init_module (void) /* Loads a module in the kernel */{printk("Hello kernel n");return 0;} 
void cleanup_module(void) /* Removes module from kernel */{printk("GoodBye Kerneln");} 

Compiling the module 
# gcc -c hello.c # insmod hello.o 
The output is 
Hello kernel 
# rmmod hello.o 
GoodBye Kernel 

How init_module works? 
init_module loads the relocated module image into kernel space and runsthe module's init function. 
The module image begins with a module structure and is followed by codeand data as appropriate. 
The module structure is defined as follows: 
struct module 
{ 
unsigned long size_of_struct; 
struct module *next;const char *name; 
unsigned long size; 
long usecount; 
unsigned long flags; 
unsigned int nsyms; 
unsigned int ndeps; 
struct module_symbol *syms;struct module_ref *deps;struct module_ref *refs; 
int (*init)(void); 
void (*cleanup)(void); 
const struct exception_table_entry *ex_table_start; 
const struct exception_table_entry *ex_table_end; 
#ifdef __alpha__unsigned long gp; 
#endif 
} 
; 
All of the pointer fields, with the exception of next and refs, areexpected to point within the module body and be initialized as appropriatefor kernel space, i.e. relocated with the rest of the module. 

Return Values 
On success, zero is returned. On error, -1 is returnedand errno is set appropriately. 

Errors 
EPERM The user is not the superuser. 
ENOENT No module by that name exists. 
EINVAL Some image slot filled in incorrectly, image->namedoes not correspond to the original module name,some image->deps entry does not correspond to aloaded module, or some other similar inconsistency. 
EBUSY The module's initialization routine failed. 
EFAULT name or image is outside the program's accessibleaddress space. 

How cleanup_module works? 
cleanup_module attempts to remove an unused loadable module entry. Ifname is NULL, all unused modules marked auto clean will be removed. 
Return Values 
On success, zero is returned. On error, -1 is returned and errno isset appropriately. 
Errors 
EPERM The user is not the superuser. 
ENOENT No module by that name exists. 
EINVAL name was the empty string. 
EBUSY The module is in use. 
EFAULT name is outside the program's accessible addressspace.This simple module is called skull, short for Simple Kernel Utility ForLoading Localities. 

General flags used for compiling any driver are 
-D__KERNEL__ _DMODULE -O -Wall -I$(INCLUDEDIR) 

Note: 
The INCLUDEDIR should contain the header files of the kernel source. 
Module code has to be recompiled for each version of the kernel that itwill be linked to. Each module defines a symbol called kernel_versionwhich is defined in . In case of a version mismatch, usethe insmod -f (force) option to load the module. 

linux installation made easy

So you are on Windows and contemplating a switch. Before you do that, consider this. If you are an average Joe who uses his PC just for typing documents, watching movies, surfing the Web and listening to music, catch the first train back to Windows Land. Linux is not for you. On the other hand, if you are a born explorer with a burning desire to understand how your operating system works and to be able to control how it works, `Welcome aboard'. 
But Linux is not all cakewalk. Watch your step, for it is no merry stroll we take. It is more of journey, which will lead you right into the innards of your O/S. So lets start at the beginning--the history of Linux. 

History 

There was a time, when there was no Windows, no Microsoft and believe it or not, computers still existed. It was the age of Unix. A mostly command line based operating system which was robust, stable, mostly crash free and yet costly. Linus Torvalds (Father of Linux), at that time, was a University student from Helsinki, Finland. He had a PC but could not afford Unix and since CD ROMs were still in the research stage, piracy had not become the orde of the day. And although Unix was ideal for PCs that were networked or connected with each other, it was too big for a standalone PC an average student had. So Linus decided to make his own o/s. 
Back then, there already existed a small version of Unix called Minix that was not very popular. Linus made a new o/s of his own and named it Linux for his own name. In August 1991, he posted the o/s and its source-code on the still budding Internet with a request to anyone who may download it to make suggestions and/or improvements in the o/s and mail them back to him. A wise move. 
And nothing had prepared him for the number of responses received. People who surfed the Net in those days were mostly computer science students and Linus had made something everyone needed. What’s more, everyone could modify the o/s to personalize it. Soon hundreds of emails started pouring in. And the Linux community had been formed. 
What propelled Linux was that it was an open source O/S. i.e. the source code of the operating system was not only available to anyone who wanted it, but he/she could modify it. The only(and at that time just moral not legal) obligation was that the individual had to email the change to Linus and he would incorporate it into the Official version of Linux if he felt it was good. 
As the Internet grew in size, thousands of programmers across the world started working on Linux, each one either adding something new or correcting a flaw somewhere. Therefore all the good things got included in the official version and soon Linux flowered into a full-fledged Operating System. 
Later of course, Linus started distributing Linux under the GPU or General Public License. This entitles a user to change the source code of the O/S and distribute it, even commercially, provided he agrees to publish the change. In return he gets a copyright to that change. And this is how it is today.As an operating system, the newer versions of Linux are almost as easy to use as MS Windows. They have ‘Windows’ and ‘Taskbar’ and all the stuff but the real beauty of Linux is in the command line - the Linux Shells. 
You can install Linux and make it co-exist with your existing windows Operating System without having to reinstall Windows. And this can be done without causing any loss of your data. 


Requirements 

A hard disk with at least 1GB of free space which, after installation of Linux will become unusable for Windows till you uninstall Linux if ever. Please leave at least 50 MB free for the Windows System Minimum Hard Disk Space: 1 GB 50 MBsRecommended Hard Disk Space : 2.5 GB (This will leave at least 1 GB Free after installation) 

RAM requirements:Minimum : 16 MB RAMRecommended : 32 MB RAM 

A Linux Installation CD and a CD ROM drive.Minimum : Any distributionRecommended : Caldera Linux eDesktop 2.4 ( Latest as of Feb 2001)Or Recommended : Suse Linux 6.3 (Chip CD April 2000) or Suse 7.0 .If you can’t get the above Chip CD, you can download any Linux distribution, without its Commercial Packages from the distributor’s site if you have broadband and then burn it on a CD if you have a CD Writer. WWW.SUSE.COM , WWW.CALDERA.COM, WWW.REDHAT.COM 
OrFind the Linux User Group (LUG) in your city from www.linux-india.org or www.LinuxIndia.org. Each LUG has a mailing list and a request here will find you at least one person willing to lend you a CD. After installation you can get the CD copied commercially for about 100 bucks and it is perfectly legal. 

Your hardware specificationsThis can be mostly found in the books accompanying your computer. Find the names of your Graphic Accelerator Card (if any), Sound Card. Find out the vertical and horizontal refresh rate ranges of your monitor. If the monitor came with a book, you will find it there. Also find its maximum resolution and frequency. Most people don’t have any SCSI drives, but if you know you have one, find the name. 

A partitioning softwareWe use Partition Magic 6.0. And it is the only one I recommend. If you have Windows 98/95 Partition Magic 4 / 5 will also work. However, you can also use System Commander 2000. In case you have Windows ME installed, you will have to use Partition Magic 6.0 as nothing else will work. 
Windows installation disk and boot floppiesThese are essential in case you goof up very badly (chances of this happening are less than 5% if you read this properly). If you don’t have boot floppies, don’t fret. Partition Magic / System Commander will make them for you when you install it. If you have any means of backing up your software, please do it now. You can do so on a zip drive, a CD writer or if you have a large hard disk, on a separate partition where Windows is not installed. 


Partitioning Hard Disk 

By now you have installed Partition Magic. (P.M) here, we take P.M 6.0 as an example. Version 5.0 has the same interface. First cick on ‘Create New Partition’ in the lower left of the screen. Click Next. Now choose the Hard Disk (if you have two hard disks), on which you want to install Linux and click Next. It is advisable to install Linux on your Primary Hard Disk (The one with Windows on it). In case you have one, it is the default option. Then click on yes when it asks if you want to install a new Operating System on the partition Click Next. Choose Linux from the list of Operating Systems before clicking on Next. 

Ext2 option is chosen by default. They recommend installing Linux on a Logical Partition, do it. Click Next. Choose the recommended option in the next screen. Go to Next. If you already have more than one partition, you have to choose from where PM should derive space to install Linux. Choose the partition where you have (freed up) space for Linux and click Next. Decide the size of the partition. Enter 1000 in the MB box for 1 GB and 2000 for 2 GB. Enter at least 128 MB less than the total space you freed for Linux as we will need this for another partition called ‘Swap Space’. Enter any name you want to keep for this partition in the Label box and click Next and then Finish. 

Now they recommend creating a Swap Space partition for Linux. Click `Yes’ and then `Next’. Put the Swap Space on the same Hard Disk as your Linux partition, if you have 2 Hard Disks. Now you have to go through 3 steps in the same way as above. In the 4th step, you have to decide the size of Swap. 128 MB is enough for most people. Enter a Name (Label) if you want to before going on to Finish. Now click on `Apply changes’ and the computer will restart. PM will do the partitioning and this process will take about 15-20 minutes on a P3-450 more if you have a slower processor so be patient. 

Caution : When the computer is restarting, do not interrupt the process in any way unless asked to by the instructions on your screen. 

Installation 

We assume you have all the apparatus listed above in place along with the books etc and all info you can get about your hardware as a safeguard. We are taking Caldera 2.4 as the example, as it is the easiest. For those using SUSE, the installation is similar and almost as easy. Now you have to Put the Caldera CD in the CD-ROM and Restart your PC. Before this you need to ensure that your PC can boot from the CD ROM. This is the default for 99% PCs. But in case you are the odd one out, this can be done from the BIOS. The ideal order in which to boot disks is: 
1) Floppy 
2) CD-ROM 
3) HDD 
4) Anything Else 
The Boot order is one of the menu options in BIOS. You can start the BIOS by pressing F2 when your computer boots. Do not change anything else in the BIOS. Save the changes and restart. Now you can insert the CD in the CD Rom drive and Restart you PC. THE PC boots from the Caldera CD and you can now see a screen offering you various modes of installation. Choose the ‘VESA INSTALLATION’ mode.Now select your Language : English 

The next screen offers you a choice of your mouse. It detects the appropriate option by default. Check to see if you can move your pointer around and click things and then click Next. If it doesn’t find the appropriate model from the drop down list and choose it Next screen offers a choice of keyboards. Most people have a Generic 104 KEY keyboard. Test if all the letter and number keys are working in the space below. 

It offers a choice of your video card. We suggest you click Probe. The screen flickers for a while and then offers the right choice. If it does not, you can choose your card from the list. In the next screen you choose your video mode. Here is where you have to find the Horizontal Frequency Range of your monitor and what maximum frequency it supports. If you have a decent video card, 800 * 600 at 61 Hz will work. 640 * 480 at 60 Hz should work for most people. If not, choose a lower option like 400 * something etc. If the screen offers an option to test it, test this mode, if you can see an image similar to your Windows Desktop the configuration is OK. 

Choose 32 bpp in the lower left options and choose `No Virtual Desktop’. In the next screen choose Prepared Partition and then select the partition(s), which you formatted for Linux and the installer will format them again when you click format. Unfortunately this has to be repeated. Do not format your Windows partition by mistake or you will lose all your software. You can differentiate between the two by their drive letters. These drive letters can be known when Windows reboots after partition magic repartitions your hard drive. If you don’t know them, stop the installation reboot in windows and find them. 

In the next screen, choose the partition to be mounted as root. The 1 or 2 GB partition, which you formatted for Linux should be mounted as root and not any other partition. Select ‘Install LILO on MBR’ which is the recommended option. Later you have to choose which Operating Systems you want to boot into. Generally, the list consists of Caldera and Windows. Select `ALL’ 

Now, choose what kind of installation you want. This can be decided by the amount of Memory that each takes and how much you have freed for Linux.After that it asks you to configure your modem printer etc, from a list and your Internet service provider (ISP). Select the Time Zone : Asia Calcutta, for example. You can do this easily by clicking on Calcutta in East India on the world map above. Choose ‘Hard Ware Clock Set to Local Time’. It asks you for data like name and 2 passwords. 

Wait till installation gets over. Click Next and allow Caldera to reboot. You get a list of Operating Systems you can boot into. Choose Linux and after 1 minute you get a screen asking for your user name and password. Enter them and you have booted into Linux. 
After that Explore Learn Fiddle and if you screw up, reinsall. You can boot into Windows by selecting Windows at the boot up menu. 

And happy working with Linux. You sure will enjoy it. 

The linux file system explained

The first thing that most new users shifting from Windows will findconfusing is navigating the Linux filesystem. The Linux filesystem does things a lot more differently than the Windows filesystem.This article explains the differences and takes you through the layout of the Linux filesystem. 

For starters, there is only a single hierarchal directory structure.Everything starts from the root directory, represented by '/', and thenexpands into sub-directories. Where DOS/Windows had various partitions andthen directories under those partitions, Linux places all the partitionsunder the root directory by 'mounting' them under specific directories.Closest to root under Windows would be c:. 

Under Windows, the various partitions are detected at boot and assigned adrive letter. Under Linux, unless you mount a partition or a device, thesystem does not know of the existence of that partition or device. Thismight not seem to be the easiest way to provide access to your partitionsor devices but it offers great flexibility. 

This kind of layout, known as the unified filesystem, does offer severaladvantages over the approach that Windows uses. Let's take the example ofthe /usr directory. This directory off the root directory contains most ofthe system executables. With the Linux filesystem, you can choose to mountit off another partition or even off another machine over the network. Theunderlying system will not know the difference because /usr appears to bea local directory that is part of the local directory structure! How manytimes have you wished to move around executables and data under Windows,only to run into registry and system errors? Try moving c:windowssystemto another partition or drive. 

Another point likely to confuse newbies is the use of the frontslash '/'instead of the backslash '' as in DOS/Windows. So c:windowssystem wouldbe /c/windows/system. Well, Linux is not going against convention here.Unix has been around a lot longer than Windows and was the standard a lotbefore Windows was. Rather, DOS took the different path, using '/' forcommand-line options and '' as the directory separator. 

To liven up matters even more, Linux also chooses to be case sensitive.What this means that the case, whether in capitals or not, of thecharacters becomes very important. So this is not the same as THIS or ThIsfor that matter. This one feature probably causes the most problems fornewbies. 

We now move on to the layout or the directory structure of the Linuxfilesystem. Given below is the result of a 'ls -p' in the root directory. 

bin/ dev/ home/ lost+found/ proc/ sbin/ usr/boot/ etc/ lib/ mnt/ root/ tmp/ var/ 

/sbin - This directory contains all the binaries that are essential to theworking of the system. These include system administration as well asmaintenance and hardware configuration programs. Find lilo, fdisk, init,ifconfig etc here. These are the essential programs that are required byall the users. Another directory that contains system binaries is /usr/sbin. This directory contains other binaries of use to the system administrator. This is where you will find the network daemons for your system along with other binaries that only the system administrator has access to, but which arenot required for system maintenance, repair etc. 

/bin - In contrast to /sbin, the bin directory contains several usefulcommands that are used by both the system administrator as well asnon-privileged users. This directory usually contains the shells likebash, csh etc. as well as much used commands like cp, mv, rm, cat, ls. There also is /usr/bin, which contains other user binaries. These binaries on the other hand are not essential for the user. The binaries in /bin however, a user cannot do without. 

/boot - This directory contains the system.map file as well as the Linuxkernel. Lilo places the boot sector backups in this directory. 
/dev - This is a very interesting directory that highlights one importantcharacteristic of the Linux filesystem - everything is a file or adirectory. Look through this directory and you should see hda1, hda2 etc,which represent the various partitions on the first master drive of thesystem. /dev/cdrom and /dev/fd0 represent your CDROM drive and your floppydrive. This may seem strange but it will make sense if you compare thecharacteristics of files to that of your hardware. Both can be read fromand written to. Take /dev/dsp, for instance. This file represents yourspeaker device. So any data written to this file will be re-directed toyour speaker. Try 'cat /etc/lilo.conf > /dev/dsp' and you should hear somesound on the speaker. That's the sound of your lilo.conf file! Similarly,sending data to and reading from /dev/ttyS0 ( COM 1 ) will allow you tocommunicate with a device attached there - your modem. 

/etc - This directory contains all the configuration files for your system.Your lilo.conf file lies in this directory as does hosts, resolv.conf andfstab. Under this directory will be X11 sub-directory which contains theconfiguration files for X. More importantly, the /etc/rc.d directorycontains the system startup scripts. This is a good directory to backupoften. It will definitely save you a lot of re-configuration later if youre-install or lose your current installation. 

/home - Linux is a multi-user environment so each user is also assigned aspecific directory which is accessible only to them and the systemadministrator. These are the user home directories, which can be foundunder /home/username. This directory also contains the user specificsettings for programs like IRC, X etc. 

/lib - This contains all the shared libraries that are required by systemprograms. Windows equivalent to a shared library would be a DLL file. 

/lost+found - Linux should always go through a proper shutdown. Sometimesyour system might crash or a power failure might take the machine down.Either way, at the next boot, a lengthy filesystem check using fsck willbe done. Fsck will go through the system and try to recover any corruptfiles that it finds. The result of this recovery operation will be placedin this directory. The files recovered are not likely to be complete ormake much sense but there always is a chance that something worthwhile isrecovered. 

/mnt - This is a generic mount point under which you mount your filesystemsor devices. Mounting is the process by which you make a filesystemavailable to the system. After mounting your files will be accessibleunder the mount-point. This directory usually contains mount points orsub-directories where you mount your floppy and your CD. You can alsocreate additional mount-points here if you want. There is no limitation tocreating a mount-point anywhere on your system but convention says thatyou do not litter your file system with mount-points. 

/opt - This directory contains all the software and add-on packages thatare not part of the default installation. Generally you will find KDE andStarOffice here. Again, this directory is not used very often as it'smostly a standard in Unix installations. 
/proc - This is a special directory on your system. We have a more detailedarticle on this one here. 
/root - We talked about user home directories earlier and well this one isthe home directory of the user root. This is not to be confused with thesystem root, which is directory at the highest level in the filesystem. 
/tmp - This directory contains mostly files that are required temporarily.Many programs use this to create lock files and for temporary storage ofdata. On some systems, this directory is cleared out at boot or atshutdown. 

/usr - This is one of the most important directories in the system as itcontains all the user binaries. X and its supporting libraries can befound here. User programs like telnet, ftp etc are also placed here./usr/doc contains useful system documentation. /usr/src/linux contains thesource code for the Linux kernel. 

/var - This directory contains spooling data like mail and also the outputfrom the printer daemon. The system logs are also kept here in/var/log/messages. You will also find the database for BIND in /var/namedand for NIS in /var/yp. 
This was a short and basic look at the Linux filesystem. You do need tohave at least this basic knowledge of the layout of the filesystem tofully utilize its potential. One good place to read about the filesystemis this detailed document atwww.pathname.com/fhs/1.2/fsstnd-toc.html thatspecifies the standard structure of the Linux filesystem.

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Here is a simple, automatic battery charger built around BC337 (T1), Zener diode (ZD1) and a few discrete components.

The power supply circuit for the charger consists of a step-down transformer (X1) and bridge rectifier comprising diodes D1 through D4.The 50 Hz, 230V AC is stepped down by transformer X1 to output 15V, 1A at the secondary. The secondary output is rectified by the full-wave bridge rectifier comprising diodes D1 though D4 and fed to the anode of SCR1. For triggering SCR1, its gage is connected through R1 to the power supply.

When the mains is available, SCR1 gets triggered via R1 and the battery starts charging. When the battery voltage level goes above 12.6V, ZD1 breaks down and npn transistor T1 conducts to ground the gate voltage of SCR1.SCR1 stops conducting and the battery stops charging. Resistor R3 limits the battery charging current. Its value can be changed as per your requirement.

On the other hand, when the battery voltage goes below 12.6V, SCR1 gets the required voltage through R1 at its gate and is triggered .The battery starts charging now.

The name operational amplifier was originally given to early high-gain vacuum tube amplifiers designed to perform mathematical operations of addition,subtraction,multiplication,division,differentiation, and integration.They could also be interconnected to solve differential equations.
The modern successor of those amplifiers is the linear integrated-circuit op amp.It inherits the name,works at lower voltages,and is available in a variety of specialized forms.Today's op amp is so low in cost ,versatility,and dependability have expanded their use far beyond application envisioned by early designers.Some present day users for op amp are in the field of signal conditioning,process control,communications, computers, power and signal sources, displays, and testing or measuring systems.The op amp is still basically a very good high gain dc amplifier.
One's first experience with a linear IC op amp should concentrate on its most important and fundamental properties. Accordingly, our objectives will be to identify each terminal of the op amp and to learn its purpose, some of its electrical limitations, and how to apply it usefully.

OP AMP TERMINALS
The circuit symbol for an op amp is an arrowhead that symbolizes high gain and points from input to output direction of signal flow.Op amps have five basic terminals:two for supply power,two for input signals, and one for output.Internally they are complex.It is not necessary to know much about the internal operation of the op amp in order to use it.The people who design and build op amps have done such an outstanding job that external components connected to the op amp determine what the overall system will do.
The ideal op amp has infinite gain and infinite frequency response.The input terminals draw no signal or bias currents and exhibit infinite input resistance.Output impedence is zero ohms, and the power supply voltages are without limit. We now examine the function of each op amp terminal to learn something about the limitation of a ral op amp.

Power supply Terminals

Op amp terminals labeled +v and -v identify those op amp terminals that must be connected to the power supply. Note that the power supply has three terminals: positive, negative, and power supply common. The power supply common terminal may or may not be wired to earth ground via the third wire of line cord. All voltage measurements are made with respect to power supply common.
The power supply is called a bipolar or split supply and has typical values of +-15v. Some op amps are now designed to operate from a single-polarity supply such as +15or +15v and ground. Note that the common is not wired to the op amp. Currents returning to the supply from the op amp must return through external circuit elements such as a load resistor RL. The maximum supply voltage that can be applied between +v and -v is typically 36v or +- 18v.



Output Terminal
The op amp’s output terminal is connected to one side of the load resistor RL. The other side of RL is wired to ground. Output voltage v0 is measured with respect to ground. Since there is only one output terminal in an op amp, it is called a single-ended output. There is a limit to the current that can be drawn from the output terminal of an op amp, usually of the order of 5 to 10 mA. There are also limits on the output terminal’s voltage levels; these limits are set by the supply voltages and by the op amp’s output transistors.

Input terminals

There are two input terminals, labeled - and +.They are called differential input terminals because output voltage Vo depends on the difference in voltage between them, Ed, and the gain of the amplifier, AoL. The output terminal is positive with respect to ground when (+) input is positive with respect to, or above the (-) input. When Ed is reversed to make the (+) input negative with respect to, or below, the (-) input, Vo becomes negative with respect to ground.
We conclude that the polarity of the output terminal is same as the polarity of (+) input terminal with respect to the (-) input terminal. Moreover, the polarity of the output terminal is opposite or inverted from the polarity of the (-) input terminal. For these reasons, the (-) input I designated as inverting input and the (+) input the non-inverting input
It is important to emphasize that the polarity of vo depends only on the difference in voltage between inverting and non inverting inputs. This difference voltage can be found by
Ed= voltage at the (+) input-voltage at the (-) input.
Both input voltages are measured with respect to ground. The sign of Ed tells us

(1) the polarity of the (+) input with respect to the (-) input and

(2) the polarity of the output terminal with respect to ground.

This equation holds if the inverting input is grounded, if the noninverting input is grounded, and even if both inputs are above or below ground potential. Thus, if the polarity of Ed matches the op amp’s symbol, the output is voltage goes to +vsat. When the polarity of Ed is opposite the op amp’s symbol, the output voltage goes -vsat.

Basics of op-amp

The name operational amplifier was originally given to early high-gain vacuum tube amplifiers designed to perform mathematical operations of  addition,subtraction,multiplication,division,differentiation, and integration.They could also be  interconnected to solve differential equations.
               The modern successor of those amplifiers is the linear integrated-circuit op amp.It inherits the name,works at lower voltages,and is available in a variety of specialized forms.Today's op amp is so low in cost ,versatility,and dependability have expanded their use far beyond application envisioned by early designers.Some present day users for op amp are in the field of signal conditioning,process control,communications, computers, power and signal sources, displays, and testing or measuring systems.The op amp is still basically a very good high gain dc amplifier.
      One's first experience with a linear IC op amp should concentrate on its most important and fundamental properties. Accordingly, our objectives will be to identify each terminal of the op amp and to learn its purpose, some of its electrical limitations, and how to apply it usefully.

OP AMP TERMINALS

The circuit symbol for an op amp is an arrowhead that symbolizes high gain and points from input to output direction of signal flow.Op amps have five basic terminals:two for supply power,two for input signals, and one for output.Internally they are complex.It is not necessary to know much about the internal operation of the op amp in order to use it.The people who design and build op amps have done such an outstanding job that external components connected to the op amp determine what the overall system will do.
       The ideal op amp has infinite gain and infinite frequency response.The input terminals draw no signal or bias currents and exhibit infinite input resistance.Output impedence is zero ohms, and the power supply voltages are without limit. We now examine the function of each op amp terminal to learn something about the limitation of a ral op amp.

Power supply Terminals

Op amp terminals labeled +v and -v identify those op amp terminals that must be connected to the power supply. Note that the power supply has three terminals: positive, negative, and power supply common. The power supply common terminal may or may not be wired to earth ground via the third wire of line cord. All voltage measurements are made with respect to power supply common.
         The power supply is called a bipolar or split supply and has typical values of +-15v.  Some op amps are now designed to operate from a single-polarity supply such as +15or +15v and ground. Note that the common is not wired to the op amp. Currents returning to the supply from the op amp must return through external circuit elements such as a load resistor R_L. The maximum supply voltage that can be applied between +v and -v is typically 36v or +- 18v.

Output Terminal

The op amp’s output terminal is connected to one side of the load resistor R_L. The other side of RL is wired to ground.  Output voltage v0 is measured with respect to ground. Since there is only one output terminal in an op amp, it is called a single-ended output. There is a limit to the current that can be drawn from the output terminal of an op amp, usually of the order of 5 to 10 mA. There are also limits on the output terminal’s voltage levels; these limits are set by the supply voltages and by the op amp’s output transistors.

Input terminals

There are two input terminals, labeled - and +.They are calleddifferential input terminals because output voltage V_o depends on the difference in voltage between them, E_d, and the gain of the amplifier, A_oL. The output terminal is positive with respect to ground when (+) input is positive with respect to, or above the (-) input. When E_d is reversed to make the (+) input negative with respect to, or below, the (-) input, V_o becomes negative with respect to ground.
               We conclude that the polarity of the output terminal is same as the polarity of (+) input terminal with respect to the (-) input terminal. Moreover, the polarity of the output terminal is opposite or inverted from the polarity of the (-) input terminal. For these reasons, the (-) input I designated as inverting input and the (+) input the non-inverting input
            It is important to emphasize that the polarity of v_o depends only on the difference in voltage between inverting and non inverting inputs. This difference voltage can be found by
E_d= voltage at the (+) input-voltage at the (-) input.
Both input voltages are measured with respect to ground. The sign of Ed tells us

(1) the polarity of the (+) input with respect to the (-) input and

(2) the polarity of the output terminal with respect to ground.

This equation holds if the inverting input is grounded, if the noninverting input is grounded, and even if both inputs are above or below ground potential. Thus, if the polarity of Ed matches the op amp’s symbol, the output is voltage goes to +vsat. When the polarity of Ed is opposite the op amp’s symbol, the output voltage goes -vsat.

door bell

This circuit consists of two 555 ICs. IC1 is used functions as monostable and IC2 is wired as astable multivibrator. The loud speaker LS1 sounds a bell tone as long as the time period of the monostable multivibrator (IC1).

             The circuit is powered by a 9v battery. When switch S1 is pressed, IC1 is triggered at its pin 2 and output pin 3 goes high for a time period set using preset VR1 and capacitor C1. The high output if IC1 resets Ic2 and it starts oscillating to produce a bell tone through the loudspeaker. The frequency of oscillation of IC2 can be varied with the help of preset VR2, so various tones can be heard through loudspeaker LS1.

 

Components required

              IC1- NE555

     IC2- NE555

LS1 (loudspeaker)-8Ώ, 1W

VR1-100k

VR2-100k

R1- 4.7K

R2- 10k

R3-1K

C1-33μ

C2-0.01 μ

C3- 0.01 μ

C4- 0.01 μ

C5-100 μ, 25