How PDAs Work

The PDA Computer
The parts that can make up a PDA
The parts that can make up a PDA

Microprocessors and Memory

Like standard desktop and laptop computers, PDAs are powered by microprocessors. The microprocessor is the brain of the PDA, and it coordinates all of the functions according to programmed instructions. Unlike desktop PCs and laptops, PDAs use smaller, cheaper microprocessors. Although these microprocessors tend to be slower than their PC counterparts, they're adequate for the tasks that PDAs perform. The benefits of small size and price outweigh the cost of slow speeds.

A PDA doesn't have a hard disk. It stores basic programs (address book, calendar, memo pad and operating system) in a read-only memory (ROM) chip, which remains intact even when the machine shuts down. Your data and any programs you add later are stored in the device's random-access memory (RAM). Information in RAM is only available when the device is on. Due to their design, PDAs keep data in RAM safe because they continue to draw a small amount of power from the batteries even when you turn the device off.

Less powerful PDAs have lower amounts of RAM. However, many application programs take up significant memory space, so most models have more memory. Also, Pocket PC devices generally require more resources and have even more RAM. To provide additional memory, many PDAs accept removable flash media add-on cards. These are handy for storing large files or multimedia content, such as digital photos.

Some newer PDAs, such as the Palm Tungsten E2, use flash memory instead of RAM. Flash memory is non-volatile, which means it preserves the data and applications it stores -- even when all battery power is depleted.

Operating Systems

The operating system contains the pre-programmed instructions that tell the microprocessor what to do. The operating systems used by PDAs are not as complex as those used by PCs. They have fewer instructions, which require less memory.

Here's an inside view of a PDA. The circuit board folds away from the screen. In the middle of the single-layer circuit board is the microprocessor, and to the left and above are the memory chips.

PDAs and smartphones typically have one of two types of operating systems: Palm OS or Windows Mobile. However, RIM makes a specific OS for its BlackBerry devices, and the Symbian OS operates some smartphones.

In the next section, we'll look at the other parts that make up a PDA.