Hardware

• Computer system: any system which can run either VAX/VMS or UNIX operating systems. MIDAS implementations have been made on a large number of systems from vendors e.g. VAX stations, DEC stations, SUN SPARCstations, HP 700 series, IBM RS/6000 systems, PCs. The availability for a specific system can be checked by asking the MIDAS Hot--line.
• Memory: depending on the number of users of the systems but normally at least 8 Mbyte. A physical memory that is too small may significantly reduce the performance due to swapping of data to disk.
• Disk: the full MIDAS system requires of the order of 100 Mbyte of disk storage depending on the type of CPU. During installation an extra 10 Mbyte should be available for temporary files such as object code. The size of the system can be reduced in three ways: a) source files can be deleted after implementation, b) help--files can be removed if on--line help is not required, and c) parts of the system which are not used ( e.g. crowded field photometry or echelle packages) need not be loaded. Implementations using shared libraries are available on some systems ( e.g. SPARCstations and PCs). This reduces the needed disk space significantly.

  A typical disk size for a single user system is approximately 200 Mbyte assuming 60 Mbyte for the operation system, 80 Mbyte for MIDAS, and 50-100 Mbyte for a user with 2--dimensional data.

• Terminals: any alpha-numeric terminal can be used. MIDAS can either work in a simple line-by-line mode or provide special features such as line editing by using a terminal definition file for special terminal features.
• Graphic display: the graphics software of MIDAS uses the device independent plotting library AGL made by the italian ASTRONET. Drivers for a significant number of different devices are available e.g. Tektronix 4010/4015, X Window System, version 11 and PostScript (see a complete list in Chapter ). It is possible to write drivers for devices for which none exist (see the AGL driver manual).
• Image displays: MIDAS uses the Image Display Interfaces which provides a general interface to image display devices. IDI-routines are available for DeAnza IP 8500 and X Window. X Window System, version 11, will be supported as the general interface to workstations. Other devices can be used if an appropriate set of IDI-routines are written. A list of currently available IDI-routines can be obtained from the User Support Group.