INT - x86-64 instruction reference

intCall to interrupt procedure 
Causes a software interrupt through the given vector number, from 0 to 255.
8086 and later
Intel's reference: INTn/INTO/INT3/INT1 
CFPFAFZFSFTFIFDFOF –––––0●––
● set from the result
0 always 0
– not changed
Forms  int   
Operands imm8 An 8-bit immediate, -128 to 255. Instructions that sign-extend it to a wider operand interpret the byte as -128 to 127; shift counts do not use this sign extension. 
The code generated by the INT instruction is always two bytes
long: although there are short forms for some INT instructions,
NASM does not generate them when it sees the INT mnemonic. In
order to generate single-byte breakpoint instructions, use the
INT3 or INT1 instructions instead.