path: root/subx/ex4.subx

## read a character from stdin

# opcode        ModR/M                    SIB                   displacement    immediate
# instruction   mod, reg, Reg/Mem bits    scale, index, base
# 1-3 bytes     0/1 byte                  0/1 byte              0/1/2/4 bytes   0/1/2/4 bytes
# 0: e_entry = 0x08048054
  ## read(1, x, 1)
  # fd = 1
  bb                                                                            1/imm32       # copy 1 to EBX
  # set location to write to
  b9                                                                            00 90 04 08   # copy 0x08040000 to ECX
  # size = 1 character
  ba                                                                            1/imm32       # copy 1 to EDX
  # syscall = read
  b8                                                                            3/imm32       # copy 3 to EAX
  # call
  cd                                                                            128/imm8      # int 80h

  ## exit(EBX)
  b8                                                                            1/imm32       # copy 1 to EAX
  cd                                                                            128/imm8      # int 80h

# vim:ft=subx:nowrap