. Real-time  clock —Allows real-time clock to be updated internally or externally Consult  your  technical  manuals  for  exact operations  used  in  the  different  computer  operating modes. MAN/MACHINE INTERFACE FUNCTIONS The man/machine interface is used to perform a variety of general functions. These functions include, but are not limited, to the following: l o l l l l l l l Configure the computer/processor system Apply power Enter data and display data Execute internal diagnostics Execute bootstrap Initiate operational programs Execute auto restart operations Execute diagnostics Patch or revise software Not every man/machine interface function applies to every type of computer; therefore, we look at the three  general  types  of  computers  (microcomputers, minicomputers,  and  mainframes)  and  give  an  overview of the man/machine interfaces used for each particular type  as  it  applies  to  you.  We  do  not  address microprocessors  as  such.  We  consider  them  as replaceable or repairable components of the larger device. We also do not discuss peripheral devices used for  system  control  and  configuration  operations.  The following  discussion  covers  only  those  man/machine interface   devices   considered   as   components   or assemblies of the particular type of computer. With all types   of   computers,   consult   the   appropriate documentation  for  your  system  to  ensure  proper operation. This  last  statement  cannot  be  over emphasized. Microcomputers The   man/machine   interfaces   used   with   the microcomputers you maintain will be system oriented. Let’s take a look at the options available to you for microcomputers. CONFIGURE    THE    PROCESSOR.— Microcomputer systems are designed to be flexible in their   configuration. You can easily modify most desktop  systems  to  incorporate  additional  disk  units (hard  or  floppy),  expanded  memory,  other  components, as  well  as  specific  operator  requirements.  The ROM-based firmware that the system uses for booting the operating system as well as other system software must   be   configured   for   the   current   system interconnection scheme. Three methods are commonly used to inform the processor of the system configuration. They are DIP switches,  jumpers,  and  battery  protected  storage  of configuration  data. DIP   Switches.—Dual-inline   package   (DIP) switches are made to be instilled into integrated circuit sockets or board connections. Each switch in the package (fig. 8-18) normally indicates one of two conditions by its ON/OFF status. The board mounted DIP switches are designed so you can manually position them  during  component  installation,  removal,  or  initial system  configuration  to  inform  the  processor  of  the availability of the particular components as well as the requirements of the system operators. They affect such operations as video display (color and resolution) and port(s) selections. Individual switches or combinations of two or three switches are used to specify a variety of configuration   options. Jumpers.  —In some units, jumpers are used to make additional configuration changes. Jumpers (fig. 8-19) can be likened to dual-inline package (DIP) Figure 8-18.—DIP switches. 8-16