Volatile?

[Shraddha]

What does volatile keyword actually used for?

 

[Carramba]

Shraddha skrev:

What does volatile keyword actually used for?

http://publications.gbdirect.co.uk/c_book/chapter8/const_and_volatile.html

nice explanation

 

[Malcolm McLean]

What does volatile keyword actually used for?

It means "read this value from memory every time you use it". Normally all
you will achieve is to slow down the computer. However sometimes the
variable might be modified by something outside of the program. Also
occasionally you want to force a memory read for timing purposes.

For instance if we make a loop counter "volatile" then effectively the
compiler cannot optimise the loop away, because it doesn't know how many
times it will need to step through it. So we might have a fairer comparison
of run times.

 

[Jack Klein]

It means "read this value from memory every time you use it".

[snip]

That's part of what it means, but at least as important is:

Write all modified values to the object, and write them in the order
in which the writes appear in the source.

Consider:

extern volatile unsigned char *Uart_Tx_Register;

void send_char(char ch)
{
if ('\n' == ch)
*Uart_Tx_Register = '\r';
*Uart_Tx_Register = ch;
}

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.learn.c-c++
http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html