How much memory can a program use at most?

In virtual address mode , The memory capacity that a program can use is the same as the physical memory of the computer （ That is, your memory module ） It doesn't matter. , It is determined by the value range of the virtual address .

32 Bit operating system

stay 32 Bit operating system , The maximum memory a program can use is 4GB, That is to say 2 Of 32 Power . Even if your computer has 16G My memory module is useless , The rest 12G Can only be idle .

Let you buy so much memory , Waste it ！

64 Bit operating system

stay 64 Bit operating system , Theoretically, the range of virtual addresses that can be accessed is 2^64.

It's a big value , It's almost infinite , In terms of current technology , Not only can the physical memory be so large ,CPU The addressing capability of is not so big , Realization 64 Bit long virtual addresses only increase the complexity of the system , No benefits .

Windows and Linux All have restrictions on virtual addresses , Use only the low address of the virtual address 48 position （6 Bytes ）, The total virtual address size is 2^48 = 256TB.

256TB It's too big , Only in the age of quantum computer can we use so much memory ！

The operating system also takes up memory

The operating system is also a program , And is the leader of other procedures , Always manage other programs , Whoever disobeys will be punished , Let him collapse .

conversely , Ordinary programs also need the help of the operating system , Especially when accessing hardware , For example, allocate memory 、 Open the file on the hard disk 、 Painting on the screen, etc .

The operating system and ordinary programs love and hate each other .

In order to achieve the purpose of love and hate , The operating system also takes up some memory .

32 Bit Windows Default occupation 4GB Medium 2GB, The program can only use the rest 2GB.

32 Bit Linux Default occupation 4GB Medium 1GB, The program can only use the rest 3GB.

64 Bit Windows Default occupation 256TB Medium 248TB, The program can only use the rest 8TB.

64 Bit Linux Default occupation 256TB Medium 128TB, The program can only use the rest 128TB.

Of course , The memory occupied by the operating system can be changed by setting .

In total , How much memory a program can use depends on the operating system , Different operating systems 、 Different digits will be different .

Now most of the operating systems we use are 64 It's a bit , Memory is enough , So if you are not short of silver , Just try to upgrade the memory , the more , the better , It won't be wasted .