# System Functions

- [millis()](/latest_en/api-reference/funcs/systemfunc/millis.md): Obtain the system time, \[ms].
- [delay()](/latest_en/api-reference/funcs/systemfunc/delay.md): Waiting for time by polling.
- [delayMicroseconds()](/latest_en/api-reference/funcs/systemfunc/delaymicroseconds.md): Wait for time by polling (specified in μsec).
- [random()](/latest_en/api-reference/funcs/systemfunc/random.md): Generates an random number.