Hi Riya,
From Whatever you have explained till now I would like to give you some information which might be useful to you.

Many microntrollers in the MCS-family have in-built Program memory. Refer to their data sheets for the amount, and type (EPROM, Flash, ROM,OTP,etc) of Program memory.
Now get your hex (or Bin) file ready to be downloaded into the program memory.
There are many ways of prorgamming the program memory of the microcontroller.
Two of them are :

1. Parallel programmer: These have a cable which is used for reading the hex(or bin) from the computer using the Serial Port/Parallel Port/etc. of the computer. They give a dedicated software for sending the Hex(or Bin) file to the Programmer through this cable. You insert the CPU into the socket provided on the programmer. Using further instructions (as per the programmer) you can write the Hex (or Bin) file into the CPUs program memory.

2. ISP: In-system programming: Using this method you do not need a programmer at all !!! Make a provision in your circuit board to bring out certain pins of the CPU on a connector, with very few additional passive components and some driver ICs (which are easily available), you can directly write the Hex File into the CPUs program memory. The programming software(s) are freely available on the net.

The above are the methods of transfering your hex file into the program memory of the CPU. The above is just an overview; but enough for you to take a decision of the programmer. Remember each one has got its own advantages and disadvantages.

Since your question was how to write the data in RAM into the CPUs Program memory; here is my suggestion:

If you have selected a CPU that does not have IAP: your product requirement is overdesign, unecessary, useless, bad design of the product, etc. ... and above all: WRONG desicion of selecting the CPU.

The best way, is to choose a CPU which allows IAP.
There are some type of CPUs which support IAP (In-Application Programming). You have to include a short routine in your source code, and you can directly write the data into the CPUs program memory (unused area of the program memory). There are some limitations to this method.

So if you need further clarification post your exact requirement, with reference to the above information.

AND PLEASE DO NOT EVER USE SMS, WHENEVER YOU ARE POSTING ON THIS FORUM (or on any forum).

Please Note: In case you are not aware: All capital letters means shouting.

Bye,
From Mr. Kiran V. Sutar.