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2.1 Defining the output terminal

Before an image can appear on a terminal's screen, the terminal must first be selected. This selection, performed by programs DEVICE  and DEFDEV , must imperatively precede the description of the objects.

To choose a terminal interactively  and initialize it totally for input and output, we use DEFDEV 

      SUBROUTINE DEFDEV(DEVIC, PAROUT, PARIN, CPARAM)
      INTEGER DEVIC, PAROUT(10), PARIN(10) 
      CHARACTER*(*) CPARAM

which defines a terminal interactively; this subroutine poses ad hoc questions and initializes the terminal for output and, in certain cases, input.

Input:

DEVIC, where:

• If DEVIC = 0: The user chooses a terminal interactively. The terminal number chosen is stored in DEVIC and is used if necessary. PAROUT, PARIN and CPARAM contain the initialization parameters corresponding to this terminal;

• If DEVIC > 0: The subroutine chooses terminal DEVIC and poses other questions. It returns the supplementary parameters in PAROUT on exit from this terminal, and in PARIN on entry to this terminal;

• If PAROUT(i) is a string: PAROUT(i) is the number of characters (of the order of 80) in the string stored in CPARAM. If there are several strings, they are concatenated in CPARAM;

• If DEVIC < 0: The subroutine chooses terminal |DEVIC| and does not poses any additional questions. It returns the initialization parameters in PAROUT, PARIN and CPARAM.

      SUBROUTINE DEVICE(N, IPARAM, CPARAM)
      INTEGER N, IPARAM(*)
      CHARACTER*(*) CPARAM

Input:

N, the terminal number, where:

• If N > 0: Initialize terminal number N;

• If N = 0: Enumerate the terminals available;

• IPARAM is an array containing complementary parameters. In general, it is not necessary to initialize it. For more information about this array refer to the paragraph concerning the description of terminals;
• CPARAM is an array of complementary parameters.

Remark:

DEVICE only initializes the terminal on exit. To initialize the terminal on entry, we need to use program DEVICI  described in the section on input management.

Subroutine ENDDEV  indicates the end of utilization  of a terminal.

 

      SUBROUTINE ENDDEV(N)
      INTEGER N

Input:

N, the terminal number.