How to measure a time difference in miliseconds?

[TomASS]

Hi,

I'ld like to measure a time difference (in miliseconds) between two operations. How to get a current time in milliseconds?
for example

int microStart = function_time_in_miliiseconds();
operationr1();
int microEnd = function_time_in_miliiseconds();
ind difference = microEnd-mircoStart;

int microStart = function_time_in_miliiseconds();
operationr1();
int microEnd = function_time_in_miliiseconds();
ind difference = microEnd-mircoStart;

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thanks