user19942: I am trying to upload a single program to a number of Arduinos one by one. But it is time consuming. So I would like to know if there is any way to upload the code at once to multiple Arduinos.
I have tried as follows:
3 Arduino with all the Rx, Reset, Vcc, Gnd line connected to each other. Only pin left is Tx line. So I just connect the Tx line of one arduino and program it and so on.
Is there any other way?

user21504: Arduino uses a microcontroller from Atmel and uses a programming tool that is designed for development use and not for production programming. 
What you are looking for are tools that are called "production programming tools". Atmel has a nice documentation which describes their different programming solutions: link.

user27125: Are you programming them for the first time or doing a update?
If is the first programming, I cant see another way. 
Otherwise, If is a update and your Arduino have a Wifi module you could try something like an update on the air, where you put your new firmware in a server for example and all devices updates yourself automatically or by a command.
Google for Arduino OTA (on the air) you will get a lot of source code and examples of doing that.

19942: <p>I am trying to upload a single program to a number of Arduinos one by one. But it is time consuming. So I would like to know if there is any way to upload the code at once to multiple Arduinos.</p>

<p>I have tried as follows:</p>

<p>3 Arduino with all the Rx, Reset, Vcc, Gnd line connected to each other. Only pin left is Tx line. So I just connect the Tx line of one arduino and program it and so on.</p>

<p>Is there any other way?</p>
 21504: <p>Arduino uses a microcontroller from Atmel and uses a programming tool that is designed for development use and not for production programming. </p>

<p>What you are looking for are tools that are called "production programming tools". Atmel has a nice documentation which describes their different programming solutions: <a href="http://www.atmel.com/Images/Atmel-42215-Production-Programming-of-Atmel-Microcontroller_AP-Note_AT06015.pdf" rel="nofollow">link</a>.</p>
 27125: <p>Are you programming them for the first time or doing a update?</p>

<p>If is the first programming, I cant see another way. </p>

<p>Otherwise, If is a update and your Arduino have a Wifi module you could try something like an update on the air, where you put your new firmware in a server for example and all devices updates yourself automatically or by a command.</p>

<p>Google for Arduino OTA (on the air) you will get a lot of source code and examples of doing that.</p>
