commands for minicomputers are also specific. Refer to their system manuals and desktop guides for details. The  operational  software  a  microcomputer  uses  can be off-the-shelf software or it can be software designed by an outside support activity to meet the specific requirements  of  a  platform  or  system.  Before  a microcomputer may be used, you must configure and set up the software. When configuring and setting up the software for a microcomputer, there are several things you must be aware of. The operating system must be customized to the hardware of the computer system.  This  can  be  accomplished  by  following  the step-by-step procedures in the users/owners manual. You will use operating system commands to setup the software to execute the program exactly as you have specified.  For  example,  you  could  specify  to  the operating  system  program  to  automatically  load  a  word processing program when the computer is turned on. You may want a beeper to alert you to a given situation such as when certain error conditions occur. You can set this. When using applications software with your operating system, you must ensure that the application software is compatible with the operating system. The application software will also use commands to execute its  functions.  Refer  to  operating  systems  and application software users manuals for details. ONLINE AND OFFLINE MODES OF OPERATION Modes of operation are designed into the data systems and can be selected through hardware or software  manipulation.  Basically  you  can  operate  the computer either in an online or offline mode. What the computer can do in these modes depends on the type of computer and the software. Online When  a  computer  is  in  the  online  mode  of operation, it is performing operational functions. It is interfacing  with  other  computers,  peripherals,  display systems, and communication systems to perform many tasks. And operationally, this means you must rely on the  loaded  software  for  the  computer  to  perform  its functions. The type of software the computer will use online will depend on the platform of the system (tactical, tactical support, and nontactical). A computer may perform the following types of operations in the online  mode: Operational  (includes  application  software) 1-12 Maintenance   (only   when   the   computer’s memory  is  large  enough  to  accommodate  the software can maintenance be performed while the operational program is still running) Offline In the offline mode of operation, a computer is limited to performing maintenance. The computer can be either powered or unpowered depending on the maintenance you are performing. When you take the computer offline, you remove the computer from controlling a whole system. The computer is limited to interfacing with only a single system, such as a display system or a peripheral system, to perform controlled tests or a diagnostic to test itself. In this mode some computers have the capability to not only operate in the run mode but other detailed steps such as instruction mode and sequence mode. These modes are quite useful for troubleshooting malfunctions that can’t be isolated  using  diagnostics  or  self-tests.  Figure  1-10 shows the operating mode selections of a mainframe computer. In the offline mode, you can perform the following types of maintenance: Preventive  maintenance —Testing the computer using program controlled tests and internal tests such as diagnostics and self-checks; and cleaning filters, heat exchangers, and so on. Corrective   maintenance  —Troubleshooting  the computer using program controlled tests and manual tests to isolate faults; and repairing faults by replacing bad parts or using solder and solderless techniques. Figure  1-10.—The  mode  selections  of  a  mainframe  computer.