SNAP SYSTEMS.— The SNAP systems are used primarily  to  reduce  the  administrative  workload associated  with  equipment  maintenance,  supply  and financial management, and personnel administration. Because   the   SNAP   systems   differ   in   their subsystem configurations, we are only listing the equipment  with  which  they  are  both  capable  of interfacing. Some SNAP systems communicate via modems  and  specialized  interfacing  techniques  and hardware.   SNAP   computers   interface   with   the following equipment: . Disk drive units l Magnetic tape drive units l Keyboard/video display units (KVDTs) .  Printers—High  speed,  display,  line,  and  word processing Some   SNAP   systems   use   specialized   com- munications  hardware  and  interfacing  methods.  They use processors, adapters, and modems. PERSONAL COMPUTER/DESKTOP MICROCOMPUTER  SYSTEMS.—  Personal  com- puter/desktop microcomputer systems (PC) software enables  PC  systems  to  perform  word  processing, database management, spreadsheets, graphics, and desktop   publishing. For  these  functions,  off-the- shelf software packages can be installed in each PC system. There are also many programming languages for  programming  the  PC;  they  include  BASIC, FORTRAN,  COBOL,  PASCAL,  C,  and  many  others. These  languages  allow  you  to  design  your  own programs  to  perform  functions  exactly  the  way  you want them. Figure 1-7 is a simplified block diagram of a PC system. A PC can interface with other hardware. The following  are  examples: Secondary storage units—hard disk drive units, floppy disk drive units, and/or tape cassette units Monitor—color or monochrome Printer Modem PCs can be operated as stand-alone systems or as remote units to a larger system. They can also be configured  in  local-area  networks  (LANs).  With LANs, the PC can talk with other PCS and share data files, peripherals, and software. COMPUTER SYSTEMS CONFIGURATIONS AND SETUPS The computer system you are working with must be correctly configured/setup or it will be useless for operational  purposes. You will need to be able to configure and set up the computer system for both operational  purposes  and  for  maintenance.  You  need  to be aware of two things—the hardware and the software. Figure  1-7.—A  simplified  block  diagram  of  a  PC  system. 1-9