The difference between program and storage memory

Your device has two kinds of main (internal) memory: program memory and storage memory.
Main Memory
Main memory is the internal memory of the device, and it is divided into two types: Program memory and Storage memory.
Program memory
Program memory is temporary memory that programs use when they are running. This can be compared to the RAM (Random Access Memory) of a desktop PC. When you look at a spec sheet for a Windows Mobile device, you'll see this listed as RAM or SDRAM. Windows Mobile 5.0 Pocket PCs and Smartphones use all of the RAM for program memory.
Storage memory
Storage memory is used to save files and programs. All WM5 devices use flash ROM for file storage. Flash ROM is "non-volatile" memory, which means that you don't lose data stored there if the battery dies. Microsoft refers to it as "persistent storage." The Windows Mobile OS and applications are pre-installed in a portion of the flash ROM.
Pre-WM5 Pocket PCs, however, do not use flash ROM for Storage Memory, but instead use a portion of the RAM to store program and data files. If the battery dies on a pre-WM5 device, any program installed in Main Memory or data files saved to Main Memory are lost. Hence, it is particularly important to back up pre-WM5 Pocket PCs.
Storage memory can be added to Windows Mobile devices using CF, SD, miniSD, and microSD storage cards. These use flash ROM technology. Once they are inserted into a card slot on the device, they appear in the File Explorer or File Manager menu.

Here are 2 more types of

Here are 2 more types of memory:
Code Memory

Code memory is the memory that holds the actual 8051 program that is to be run. This memory is limited to 64K and comes in many shapes and sizes: Code memory may be found on-chip, either burned into the microcontroller as ROM or EPROM. Code may also be stored completely off-chip in an external ROM or, more commonly, an external EPROM. Flash RAM is also another popular method of storing a program. Various combinations of these memory types may also be used--that is to say, it is possible to have 4K of code memory on-chip and 64k of code memory off-chip in an EPROM.

When the program is stored on-chip the 64K maximum is often reduced to 4k, 8k, or 16k. This varies depending on the version of the chip that is being used. Each version offers specific capabilities and one of the distinguishing factors from chip to chip is how much ROM/EPROM space the chip has.
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However, code memory is most commonly implemented as off-chip EPROM. This is especially true in low-cost development systems and in systems developed by students.
On-Chip Memory

As mentioned at the beginning of this chapter, the 8051 includes a certain amount of on-chip memory. On-chip memory is really one of two types: Internal RAM and Special Function Register (SFR) memory. The layout of the 8051's internal memory is presented in the following memory map.

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