2. External Memory Because of the amount of information that CAD/CAM has to process, large-capacity external memories are particularly important. A large amount of information to be processed by the host: such as various software, graphics libraries, and databases are stored in the external memory, and are transferred to the memory through the host to receive CPU processing. At present, external storage mainly includes hard disks, floppy disks, tape drives, optical disks, magneto-optical disks (M), and newly-launched DVD disks. CDs and DVDs will play a unique role in CAD/CAM due to their large capacity and long storage time.
3. The input/output device CAD/CAM system requires high precision and speed of input and output devices because of its unique characteristics. The input device has a digitizer, a graphics tablet, a graphic scan input device and a keyboard, etc.; the output device has a plotter, a printer, a pen plotter, a hard copy machine, and the like. The optical graphic scanning input device has a tendency to replace the digitizer. The optical graphic scanning input device has high precision and high speed, and the scanned image can be edited after being vectorized.
In addition, graphic displays (CAD/CAM systems generally use 20-inch, resolution is divided into 1024 × 768 or 1280 × 1024 graphics display), communication interfaces and production devices (such as data machine tools, automatic test equipment, etc.) are also important for CAD / CAM systems hardware equipment.
Second, the software
While the CAD/CAM system hardware is constantly evolving, the software technology associated with it has also made great progress. Today's CAD/CAM software has become a complete system. This software system can be divided into three levels: system software, supporting software and application software. The figure below shows the CAD/CAM software system.
It can be seen from the above figure that some application software can be developed and run directly under the system software, and some application software needs to have a special supporting software environment.
1. System software It is mainly used for the management, maintenance, control and operation of computers, as well as the translation, loading and operation of computer programs. It includes the following categories:
Operating system: VWS for minicomputers (PDP-II series), UNIX and XENIX for super minicomputers (such as SUN, VAX-II, etc.). There are many operating systems for microcomputers: commonly used are MS-DOS, Windows, PS/2, Os/2, UNIX, XENIX, etc. UNIX was originally an operating system on a minicomputer, and it has been ported to a microcomputer, which has played a very good role in realizing multi-user, multi-tasking and convenient software porting, development and operation. It also greatly enriched the contents of the CAD/CAM system of the microcomputer.
Language Compilation System: Used to translate programs written in high-level languages ​​into machine instructions that the computer can execute directly. At present, the most widely used CAD/CAM systems are: FORTRAN, ALGOL, BASIC, C, LISP, PAS-CAL, COBOL, etc. Among them, C language has strong graphics functions and applications are increasing. LISP is an artificial intelligence language that is often used in the development of expert systems.
2. Supporting software It is the core of the CAD software system and is a general-purpose software developed to meet the common needs of some users in CAD/CAM work. Due to the rapid expansion of the field of computer applications, there has been great progress in supporting software development and development, and commercialization support software has emerged one after another. The general ones can be divided into the following categories:
Computer analysis software: mainly used for various numerical calculation problems in engineering design. Among them, ANSYS, NASTRAN and large-scale dynamic analysis software ADAMS are among the most popular ones.
· Graphics support software system: It can be divided into graphics processing language and interactive drawing software. The former is a language that provides drawing subroutines for high-level programming languages, such as the PLOT10 graphics subroutine library of Tektronix, USA, the instructions RD/GL, DM/PL, HP/GL, etc. for plotters. The latter can generate graphics, edit (add, delete, zoom, pan, etc.) ruler and assembly and other graphics processing work in human-computer interaction form, which does not need to be programmed. These softwares are more than just AutoCAD, CADKEY, CADplan, MicroCAD, etc. on the microcomputer, they all have two-dimensional and three-dimensional drawing functions. In addition, 3D solid modeling software such as CATIA, ICEM, EVCLID, IDEAS, etc. are also included.
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