Thanks James. That clears my concept. Just one doubt, are you talking about CPU registers below? Can we get address of them? How?
Regards, Hans Raj From: [email protected] [mailto:[email protected]] On Behalf Of John Matthews Sent: Wednesday, June 10, 2009 1:27 PM To: [email protected] Subject: [c-prog] Re: Volatile variable in C --- In [email protected] <mailto:c-prog%40yahoogroups.com> , "Sharma, Hans Raj \(London\)" <hansraj_sha...@...> wrote: > > Can someone please help me understand how can I write a program which, > using volatile variable, access some memory mapped devices? If you have an 8 bit register at address 0x1234 containing an unsigned 8 bit value, then you might do something like: volatile unsigned char *const reg = 0x1234; printf("reg = %u\n", *reg); It might work without the volatile, but the volatile tells the compiler that the contents of the register might change outside of the thread's control eg. because another thread is modifying it. Thus it shouldn't do any optimizations which assume its value is constant between accesses. -------------------------------------------------------------------------- This message w/attachments (message) may be privileged, confidential or proprietary, and if you are not an intended recipient, please notify the sender, do not use or share it and delete it. Unless specifically indicated, this message is not an offer to sell or a solicitation of any investment products or other financial product or service, an official confirmation of any transaction, or an official statement of Merrill Lynch. Subject to applicable law, Merrill Lynch may monitor, review and retain e-communications (EC) traveling through its networks/systems. The laws of the country of each sender/recipient may impact the handling of EC, and EC may be archived, supervised and produced in countries other than the country in which you are located. This message cannot be guaranteed to be secure or error-free. References to "Merrill Lynch" are references to any company in the Merrill Lynch & Co., Inc. group of companies, which are wholly-owned by Bank of America Corporation. Securities and Insurance Products: * Are Not FDIC Insured * Are Not Bank Guaranteed * May Lose Value * Are Not a Bank Deposit * Are Not a Condition to Any Banking Service or Activity * Are Not Insured by Any Federal Government Agency. Attachments that are part of this E-communication may have additional important disclosures and disclaimers, which you should read. This message is subject to terms available at the following link: http://www.ml.com/e-communications_terms/. By messaging with Merrill Lynch you consent to the foregoing. -------------------------------------------------------------------------- [Non-text portions of this message have been removed]
