About Writing Portable Code

Vermont Views is portable between PCDOS, OS/2, UNIX (including XENIX), VMS and POSIX. You may be able to port Vermont Views to other terminal-based environments. The only requirement is a C compiler that complies with the proposed ANSI C standard.

Most programs written for Vermont Views under PCDOS or OS/2 require only a few changes to operate under a terminal-based system. However, some of the capabilities of the IBM memory-mapped display may not show up on terminal displays. Also, there are certain machine dependencies that you need to handle in order to write portable code.

In particular, you should be aware that some functions behave differently in different environments and that there are some differences in input and output processing.

The differences between the terminal-based and PCDOS versions of Vermont Views are as follows:

• nInitialization and exit procedures differ.
  
  
• nSome functions are not supported under terminal-based operating systems.
  
  
• nSome functions are unique to the terminal-based operating systems.
  
  
• nSeveral functions perform differently under different operating systems.
  
  
• nInput processing and handling are different.
  
  
• nAlthough logical attributes are completely portable, the underlying physical attributes available for different terminals may cause differences in video output.
  
  
• nSupport for lines and borders differs based on the capability of the system to display certain graphics characters and attributes.
  
  
• nOutput to terminals is slow relative to the memory-mapped PC display; therefore, you will have to take care to optimize screen output whenever possible.