Project PDA

Option to change the operating system, only achievable in those PDAs that have flash ROM memory. A classic advice to system administrators says one should upgrade only if something does not work and there is a chance that an upgrade will fix the problem. Different PDAs use different versions of the operating system. For example, the Palm Zire utilizes OS v.4 and the Zire 71 uses OS v.5. If you have a specific software need, ensure that the operating system is capable of running it. Upgrading the operating system is close to impossible.

Every program running on a computer, be it background services or applications, is a process.

As long as a von Neumann architecture is used to build computers, only one process per CPU can be run at a time. Older microcomputer OS such as MS-DOS did not attempt to bypass this limit, with the exception of interrupt processing, and only one process could be run under them (although DOS itself featured TSR as a very partial and not too easy to use solution). Mainframe operating systems have had multitasking capabilities for since the late 1960's. Modern operating systems are able to simulate execution of many processes at once via multitasking even with one CPU.

Process management is an operating system's way of dealing with running multiple processes. Since most computers contain one processor with one core, multitasking is done by simply switching processes quickly. Depending on the operating system, as more processes run, either each time slice will become smaller or there will be a longer delay before each process is given a chance to run. Process management involves computing and distributing CPU time as well as other resources.

Most operatings sytems allow a process to be assigned a priority which impacts its allocation of CPU time. Interactive operating systems also employ some level of feedback in which the task with which the user is working receives higher priority. Interrupt driven processes will normally run at a very high priority. In many systems there is a background process, such as the System Idle Process in Windows, which will run when no other process is waiting for the CPU.

Many operating systems include some level of security. Security is based on the two ideas that:

• The operating system provides access to a number of resources, directly or indirectly, such as files on a local disk, privileged system calls, personal information about users, and the services offered by the programs running on the system.
• The operating system is capable of distinguishing between some requesters of these resources who are authorized (allowed) to access the resource, and others who are not authorized (forbidden). While some systems may simply distinguish between "privileged" and "non-privileged", systems commonly have a form of requester identity, such as a user name.