# Assembly ## Registers Generally, `r`-prefixed registers are 64-bit, `e`-prefixed registers are 32-bit, non-prefixed registers are 16-bit, and `l`-suffixed registers are 8-bit. For `r8-15` see the special cases below ([source](https://stackoverflow.com/a/20637866/10508498)):

64-bit register	Lower 32 bits	Lower 16 bits	Lower 8 bits
`rax`	`eax`	`ax`	`al`
`rbx`	`ebx`	`bx`	`bl`
`rcx`	`ecx`	`cx`	`cl`
`rdx`	`edx`	`dx`	`dl`
`rsi`	`esi`	`si`	`sil`
`rdi`	`edi`	`di`	`dil`
`rbp`	`ebp`	`bp`	`bpl`
`rsp`	`esp`	`sp`	`spl`
`r8`	`r8d`	`r8w`	`r8b` (`r8l`)
`r9`	`r9d`	`r9w`	`r9b` (`r9l`)
`r10`	`r10d`	`r10w`	`r10b` (`r10l`)
`r11`	`r11d`	`r11w`	`r11b` (`r11l`)
`r12`	`r12d`	`r12w`	`r12b` (`r12l`)
`r13`	`r13d`	`r13w`	`r13b` (`r13l`)
`r14`	`r14d`	`r14w`	`r14b` (`r14l`)
`r15`	`r15d`	`r15w`	`r15b` (`r15l`)

See [shellcode](https://book.jorianwoltjer.com/binary-exploitation/shellcode "mention") for writing malicious Assembly code and some examples of compiling