HP 3000 Manuals HP 3000 Manuals
16-bit Environments Native DOS DOS limits the total amount of memory available in which programs can run to 640 Kbytes. Some of this memory is used up by DOS itself, network drivers, file buffers and sundry other software that remains continuously in memory. Some COBOL utilities and applications can run in such restricted memory, but many cannot. Your COBOL system provides the utility XM which enables COBOL programs to use memory beyond the DOS limit of 640 Kbytes without requiring any modification. You can use XM to run COBOL system utilities as well as your own application programs created using these development tools. DOS does not detect any protection violations that might corrupt the operating system, but XM does this for you too. Your COBOL system allows you to build an application as a dual-mode .exe file that will run under DOS or an alternative operating system that can be either Windows or OS/2. Your COBOL utilities that are held as dual- mode .exe files have OS/2 as the alternative operating system. Windows Windows is a graphical operating system that runs on top of the DOS operating system. Unlike DOS, it is designed to allow several programs to be run at the same time as separate sessions. Each session runs in one of two environments: DOS emulation or native Windows. Windows Emulation of DOS. Your COBOL utilities, including XM, will run successfully in a DOS session using the DOS versions of the executable files and libraries. Your COBOL applications will also run successfully. If your application directly accesses DOS system routines or structures then you must Animate and run under DOS emulation. If your application directly accesses Windows system routines or structures then you cannot successfully Animate or run under DOS emulation. The terminal I-O in a DOS session is character-based and so character- based COBOL utilities or applications will generally run faster than under a native Windows session. A DOS session does not trap protection violations so the session can become corrupted. However, Windows will trap protection violations that reference memory outside the DOS session so Windows is protected. Native Windows. Your COBOL utilities will run successfully in a native Windows session, either from the file/run option or from an icon. Your COBOL utilities that are provided as dual-mode .exe files have OS/2 as the alternative run environment and so will not run correctly under native Windows. Alternative .exe files are provided for running under native Windows which are held in files that have a letter "w" appended to the name of the file. For example, if you run the utility animate, then this will run as a DOS emulation session. If you run the utility animatew, then this will run as a native Windows session. The terminal I-O in a native Windows session is graphics-based and so character-based utilities and applications will run slower than under a DOS session. A native Windows session does trap protection violations, in which case it displays an error box and abandons the application. OS/2 v1.x OS/2 is both a character and a graphical operating system. Like Windows, it is designed to allow several programs to be run at the same time as separate sessions. Unlike Windows, each session executes concurrently and runs in one of four environments: DOS emulation, Windows emulation, native OS/2 or Presentation Manager (PM) which is a graphical session. OS/2 v1.x Emulation of DOS. Your COBOL utilities, including XM, will run successfully in a DOS session using the DOS versions of the executable files and libraries. Your COBOL applications will also run successfully. If your application directly accesses DOS system routines or structures then you must Animate and run under DOS emulation. If your application directly accesses OS/2 system routines or structures then you cannot successfully Animate or run under DOS emulation. A DOS session does not trap protection violations so the session can become corrupted. However, OS/2 will trap protection violations that reference memory outside the DOS session so OS/2 is protected.