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Live_Feeds

Live Feeds are real time data, such as stock prices or fx rates, that are fetched from live feed providers and displayed on the spreadsheet.

Deriscope is capable of retrieving live feeds both synchronously and asynchronously from these
Live Feeds Providers.

The synchronous mode is the simplest and derives its name from the fact that the time demanding process of acquiring the data from the provider's server runs synchronously with everything else Excel is doing at that time.
One says that a process A runs synchronously with another process B, if both processes run on the same execution thread, which simply means that while one process is active, the other process cannot run simultaneously but must wait until the active process finishes its job.
Using thread terminology then, the synchronous mode means that the data acquisition process runs on the same thread as the main (user interface) Excel thread.

The asynchronous mode is more complex and derives its name from the fact that the data acquisition process runs asynchronously with everything else Excel is doing at that time.
One says that a process A runs asynchronously with another process B, if the two processes run parallel to each other on separate execution threads, which simply means that both processes can be active on the same time.
Using thread terminology again, the asynchronous mode means that the data acquisition process runs on the same thread as the main (user interface) Excel thread.

Deriscope implements synchronous live feeds through the Excel formula named
dsLiveGetSync

The asynchronous live feeds acquisition requires the usage of two Excel formulas, one named
dsLiveStartEngine and another one named dsLiveGetAsync
The former formula must run only once in order to start the asynchronous thread of acquiring the live data from the provider's server at regular time intervals.
The second formula simply returns the most recently acquired data.
It is declared volatile so that it automatically runs as soon as new feeds arrive and a recalculation event is raised.
Provided Excel is in automatic calculation mode, such a recalculation event is raised automatically upon the arrival of new feeds if the Auto Refresh setting is turned ON.