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  Many interrupt 21H functions introduced in DOS versions 2 and 3 require
  you to pass file and directory names in the form of ASCIIZ strings. An
  ASCIIZ string is simply a string of ASCII characters terminated by a
  single zero byte that marks the end of the string. For example, the ASCIIZ
  representation of the pathname C:\COMMAND.COM would consist of the
  following 15 hexadecimal bytes:

                                                                   null
                                                                   byte
                                                                   |
                        +------------------------------------------.-+
  Characters-----------.|C |: |\ |C |O |M |M |A |N |D |. |C |O |M |  |
                        +--------------------------------------------+
  ASCII values (hex)---. 43 3A 5C 43 4F 4D 4D 41 4E 44 2E 43 4F 4D 00

  The ASCIIZ string format is commonly used within the UNIX operating system
  and the C programming language; it is only one of many new elements with a
  C/UNIX flavor introduced in DOS version 2.0.