Hình 5,20 gốc máy tính LAN phần cứng và các mối quan hệ phần mềm trong một môi trường máy tính IBM. Với việc giới thiệu mạng đầu tiên của IBM khu vực địa phương, được gọi là các mạng máy tính, trong tháng 8 1984, IBM đã phát hành tất cả ba thành phần yêu cầu thi hành một mạng lưới IBM khu vực địa phương | 226 chapter five Figure Original PC LAN hardware and software relationships in an IBM PC environment. With the introduction of IBM s first local area network referred to as the PC Network in August 1984 IBM released all three components required to implement an IBM local area network using IBM equipment the IBM PC Network Program PC DOS and the IBM PC Network Adapter. The IBM PC Network Program was actually a tailored version of Microsoft Corporation s Microsoft Networks MS-NET software which is essentially a program that overlays DOS and permits workstations on a network to share their disks and peripheral devices. DOS also developed by Microsoft added file- and record-locking capabilities to DOS permitting multiple users to access and modify data. Without file- and record-locking capabilities in DOS custom software was required to obtain these functions without them the last person saving data onto a file would overwrite changes made to the file by other persons. Thus DOS provided networking and application programmers with a set of standards they could use in developing network software. Included on the IBM PC Network Adapter card in ROM is an extensive number of programming instructions known as NetBIOS. The middle portion of Figure illustrates the hardware and software components of an IBM PC LAN network. When the IBM Token-Ring Network was introduced NetBIOS was removed from the adapter card and incorporated as a separate software program activated from DOS. The right-hand column of Figure illustrates this new relationship between hardware and software. At first NetBIOS was designed to operate with Token-Ring adapter cards. Later IBM extended NetBIOS to work with CSMA CD Ethernet adapter cards. networking hardware and software 227 Due to the standardization of file-and-record locking under DOS any multiuser software program written for DOS Version or later will run on any LAN that supports this version of DOS. Although DOS .