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Types of Memory in Symbian OS
Random Access Memory (RAM)
RAM is the volatile execution and data memory used by running programs. Applications vary in how much RAM they use, and this also depends on what the application is doing at the time. For example, a browser application loading a web page needs to allocate more RAM for the web page data as it’s loaded. Also, the more RAM space you have, the more programs you can run on your smartphone at once. Typically, mobile phones have between 7 and 30MB of RAM available for applications to use.
Read Only Memory (ROM)
The ROM is where the Symbian OS software itself resides. It includes all the startup code to boot the device, as well as all device drivers and other hardware-specific code. This area cannot be written to by a user, although some of it can be seen by the file system as drive z:. Viewing the z: drive will show all the built-in applications of the OS, as well as the system DLLs, device drivers and system configuration files. For added efficiency, code in ROM is executed in place – i.e. it is not loaded into RAM before executing. Typically a phone has between 16 and 32MB of ROM.
Internal Flash Disk
The internal flash acts like a disk drive and allows for reading and writing files to it via the Symbian OS file system. The file system is fully featured and supports a hierarchical directory structure, with very similar features to those you would find on high-end operating systems. The internal flash drive is represented as the c: drive to the file system. This memory contains user-loaded applications, as well as data such as documents, pictures, video, bookmarks, calendar entries, etc.
The size of the internal flash disk varies with the phone, but it can be quite generous. For example, the Nokia 9500 has 80MB of internal flash space available to the user. On many phones, however, available internal user space is significantly less. The Nokia 6600, for example, has 6MB of flash space available to the user.
Removable memory cards
Memory cards act as removable disk drives and allow you to expand the storage provided internally. You can also read from and write to a memory card just as to the internal disk – including operations such as saving user data, and even installing applications. This card is treated as another disk volume by the file system and is represented by a drive letter such as d: or e: (this varies between phones). The memory card formats (MMC and SD are examples) and available sizes vary by phone. Memory card sizes can vary from 16MB (or even less) to 32GB.