what is : int x and int 0x80

[mIXpRo]

how does the compiler/assembler differenciate between those two commands ,
is because one starts with a number ??

[Jan Pasierb]

The

int x

reserves (usually) 4 bytes for a decimal number;

int 0x80

also declares an integer but in a hexadecimal form: http://en.wikipedia.org/wiki/Hexadecimal

0x stands for hexadecimal, and 80 is just 128 in decimal.

EDIT: also it is mainly used to manipulate bits so unless you're doing that, then you won't be needing octal or hexadecimal in your programs.

[modoran]

0x prefix means that what follows is a number in hexadecimal format.
0x80 means: 00000000 00000000 00000000 10000000 (little endian notation)

[mIXpRo]

in linux kernel :
we use "int 0x80" for calling interrupt (in this case system_call)
how can you explain that ?
why didn't the compiler declared it as integer instead it called an interrupt ??

thnx for the quick replay

[Disch]

int 0x80; is not valid C++. It will give you an error in any C++ compiler. Variables cannot be in "hexadecimal form". hexadecimal/decimal/octal/binary forms are merely different textual representations of the same number. They do not change how that number is stored in the computer.

int x; creates a variable of type 'int' which is named 'x'.

x = 0x80; assigns the hexadecimal value $80 to the variable 'x'. In this case it is basically the same as saying this: x = 128;

mIXpRo wrote:

in linux kernel :

The Linux kernel has absolutely nothing to do with C++. It can (and apparently does) mean something entirely different in that context and trying to compare the two is pointless.

[Cheraphy]

mIXpRo,

int 0x80 is assembly, it has nothing to do with the compiler.

[zienke]

int x; creates a variable of type 'int' which is named 'x'.

x = 0x80; assigns the hexadecimal value $80 to the variable 'x'.

[mIXpRo]

xander337

thnx this is the answer