Can you store all of the possible (Java) byte numbers on your laptop memory?

Q- Can you store all of the possible (Java) byte numbers on your laptop memory?
A- Probably yes. To build the answer, let's follow these steps:

1- How much memory 1 byte uses in Java?
8 bits (= 2^3 bits).
        Please check this post and this one on a new window.

2- How many possible representations of numbers in byte are available in Java?
256 (=2 ^ 8) possibilities, which can vary between -2^7 and +2^7 -1.
        Please check the reference on a new window.

3- How much memory is needed to store all the possible representations of numbers in byte?
2 K bits or 256 bytes  (256 x 8 bits = 2^8 * 2^3 = 2^[8+3] = 2^ 11 bits).
      
4- How much memory is available on your laptop?
I don't know, but you probably have enough!



http://interviewqa4java.blogspot.com/2014/02/how-many-bytes-are-in-1-gb.html

How many bytes are in 1 GB?

Q) How many bytes are in 1 GB?
We could approximate that 1 Gigabyte has 1 billion bytes, but the correct answer is  2^30 bytes.

How can I remember this answer in the future? Well here is one trick to always remember this.  Please read how to build the following table:

1. Starting with 1 byte = 2^0 bytes, make a table multiplying the previous row by 2, or just annotate the next power of 2:   2^0, 2^1, 2^2, 2^3, etc.
2. Once you reach 2^10 bytes, you can call it  1 KB (which is not 1,000, but 1024 bytes) 
3. For 2^10 to 2^19, the table mirrors the first 10 rows, except for we add the unit K (Kilo). So 2^10 B is 1 KB, 2^11 B is 2 KB, 2^12 B is 4 KB, and so forth.
4. Once you reach 2^20 bytes, you can call it  1 MB (which is not precisely 1million bytes, but 1024^2 bytes)
5. The rule #3 is analog for 2^20 to 2^29,  2^30 to 2^39, etc. So 2^25 B [= 2^(20+ 5) B] is 2^5 MB or  32 MB and 2^37 [= 2^(30+ 7) B] is 2^7 MB 128 GB.

Decimal (Bytes)	Digital Storage (Bytes)
2^0	1
2^1	2
2^2	4
2^3	8
2^4	16
2^5	32
2^6	64
2^7	128
2^8	256
2^9	512
2^10	1 K (1024)
2^11	2 K
2^12	4 K
...	...
2^20	1 M (1024^2)
2^21	2 M
...	...
2^30	1 G (1024^3)
2^40	1 T

How many bits are in 1 byte?

Q-01) How many bits are in 1 byte?
In most of the cases, 1 byte refers to 8 bits.

Q-10) - How many possible numbers can be represented with 1 bit? 
Each 1 bit can hold 2 (= 2^1) possible values: 0 or 1.

Q-11) How many possible numbers can be represented with 1 byte? 
Each 1 byte (=8 bits) can hold 256 (= 2^8) possible values: 0, 1, 10, 11, 100, 101, 110, 111, 1000, ... , 11111111 .

Binary	Decimal
00000000	0
00000001	1
00000010	2
00000011	3
00000100	4
...	...
11111101	253
11111110	254
11111111	255

How many bits are used to store a long variable, in Java?

How many bits are used to store a long variable, in Java?
64-bits.

Here are the primitive data types in Java and their sizes:

• byte       8-bits
• short    16-bits
• int        32-bits
• long     64-bits
• float     32-bits
• double 64-bits
• char     16-bits
• boolean  unknown (I know it seems weird why the answer is not 1-bit. If you know the reason, please add a comment!)

 
 For more details, check the reference.