Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I think you are mixing up two concepts. One, how does the C++ language store variables in memory. Two, how does the computer and operating system manage that memory. </p> <p>In C++, variables can be allocated on the stack, which is memory that is reserved for the program's use and is fixed in size at thread start or in dynamic memory which can be allocated on the fly using new. A compiler can also choose to store the variables on registers in the processor if analysis of the code will allow it. Those variables would never see the system memory. </p> <p>If a variable ends up in memory, the OS and the processor chip set take over. Both stack based addresses and dynamic addresses are virtual. That means that they may or may not be resident in system memory at any given time. The in memory variable may be stored in the systems memory, paged onto disk or may be resident in a cache on or near the processor. So, it's hard to know where that data is actually living. If a program hasn't been idle for a time or two programs are competing for memory resources, the value can be saved off to disk in the page file and restored when it is the programs turn to run. If the variable is local to some work being done, it could be modified in the processors cache several times before it is finally flushed back to the system memory. The code you wrote would never know this happened. All it knows is that it has an address to operate on and all of the other systems take care of the rest.</p>
    singulars
    1. This table or related slice is empty.
    1. POWhere are variables in C++ stored?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USTodd
    1. USTodd
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COIn most modern systems, the stack is not fixed in size, but is automatically extended by the operating system on the occurrence of a page fault (because of an empty stack).
      singulars
      1. PO
      1. USPaul de Vrieze
    2. COIn your answer, it becomes very clear that two different things are going on: the language's "object model" and the RAM/SwapFile/Caching system. Nice answer!
      singulars
      1. PO
      1. USxtofl
    3. COHi Paul. Thanks for the comment. You're right that the stack is virtual memory and can be paged. My point was that it was fixed in size when allocated at thread start. This is governed by the linker.
      singulars
      1. PO
      1. USTodd
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload