[c] What do numbers using 0x notation mean?

What does a 0x prefix on a number mean?

const int shared_segment_size = 0x6400;

It's from a C program. I can't recall what it amounts to and particularly what the letter x means.

The numbers starting with 0x are hexadecimal (base 16).0x6400 represents 25600.

To convert,

• multiply the last digit times 1
• add second-last digit times 16 (16^1)
• add third-last digit times 256 (16^2)
• add fourth-last digit times 4096 (16^3)
• ...and so on

The factors 1, 16, 256, etc. are the increasing powers of 16.

0x6400 = (0*1) + (0*16^1) + (4*16^2) + (6*16^3) = 25600 

or

0x6400 = (0*1) + (0*16) + (4*256) + (6*4096) = 25600 

In C and languages based on the C syntax, the prefix 0x means hexadecimal (base 16).

Thus, 0x400 = 4×(16²) + 0×(16¹) + 0×(16⁰) = 4×((2⁴)²) = 2² × 2⁸ = 2¹⁰ = 1024, or one binary K.

And so 0x6400 = 0x4000 + 0x2400 = 0x19×0x400 = 25K

It's a hexadecimal number.

0x6400 translates to 4*16^2 + 6*16^3 = 25600

SIMPLE

It's a prefix to indicate the number is in hexadecimal rather than in some other base. The C programming language uses it to tell compiler.

Example :

0x6400 translates to 6*16^3 + 4*16^2 + 0*16^1 +0*16^0 = 25600. When compiler reads 0x6400, It understands the number is hexadecimal with the help of 0x term. Usually we can understand by (6400)16 or (6400)8 or any base ..

Hope Helped in some way.

Good day,