About I/O Devices

When you install Caché, default devices are defined. These are displayed in the Devices configuration subsection of the Management Portal. Select System, Configuration, Device Settings, Devices. View the list of defined devices.

Caché ships with many default device subtypes. Each device subtype defines device characteristics, such as screen length and form-feed characteristics.

The complete list of subtypes is in the Device Subtypes configuration option of the Management Portal. Select System, Configuration, Device Settings, SubTypes. View the list of defined sub types.

Caché also ships with some magnetic tape devices defined. The complete list of magnetic tape devices is in the Magnetic Tapes Devices configuration option of the Management Portal. Select System, Configuration, Device Settings, MagTapes. View the list of defined magnetic tape devices. Magnetic tape devices can be assigned device numbers 47 through 62; by default, magnetic tape devices are assigned to device numbers 47, 48, 57, and 58. (The magnetic tape devices are also listed in the Devices option.)

You can associate one or more mnemonics with a particular Device. You use a mnemonic in response to the “Device:” prompt issued by the %IS character-based utility.

Mnemonics provide these advantages:

• They are flexible, because you can change where the mnemonic points rather than developers having to change their applications.

• They are easy for users and developers to remember. For instance, you can set up a printer device with the mnemonic Printer, or you can set up a Device ID for a file name and give it the mnemonic FILE.

You can identify devices by a number or by their operating system name. You use this identifier in OPEN commands.

You can define one or more alias values for each Caché device you define. When a user specifies an alias in an OPEN command, Caché translates it into the Device ID.

The default Device IDs that Caché provides are appropriate for most users. However, some users may want to override these defaults, particularly for magnetic tape devices. You can do this by providing an alias as part of the device's configuration settings in the Management Portal.

When you install Caché, these are the default device numbers and mnemonics for each type of device.

However, Caché also recognizes other device numbers that you can use to define devices. The following table lists the recognized default device numbers.

In addition to the mnemonics and device numbers, Caché supports I/O device types. Each internal device number belongs to one of these types. The following table shows the device types:

Before you can use a magnetic tape device with Caché, you must define it in the MagTape configuration settings of the Management Portal. Take the following steps:

1. Select System, Configuration, Device Settings, MagTapes. View the current list of magnetic tape devices.

2. Click Create New Mag Tape.

3. Enter the name of the physical magnetic tape device (for example, \\.\TAPE1).

4. Enter a device number for the magnetic tape device (within the range 47 through 62).

5. Click Save to save the changes.

You should delete outmoded magnetic tape device definitions so that your users do not inadvertently select them.

Many magnetic tape utilities (including %GIF, %GOF, %RIMF, and %ROMF) ask you whether to wait 15 seconds if the utility is not able to open the magnetic tape or cartridge tape device. If you answer “Yes” or do not respond within 10 seconds, the utility lets you decide whether to continue waiting. If you choose not to wait, the system stops trying to open the device.

If you want users of a character-based application to select a device interactively, call the %IS utility from the application. You can learn more about the %IS utility in the section Allowing Users to Specify a Device.

To select a device using the %IS utility:

1. At the Device: prompt, enter a device mnemonic.

   Predefined Mnemonic Spaces

   Mnemonic	Corresponding Device
   <ENTER>	Terminal screen
   SPOOL	Spooler
   2	Spooler
   |PRN|	Default Windows Printer
   File name: MYFILE.TXT DEV$:[TEST]MYFILE.TXT C:\MGR\MYFILE.TXT	File at path specified or, if no path specification, in current directory.
   47, 48	Magnetic tape device
   57, 58	Cartridge tape device

2. Depending on the type of device, you see another prompt:

   Device Utilities

   Device	Prompt	Valid Responses
   Terminal	Right Margin	A number representing the number of characters per line.
   Printer	Right Margin	A number representing the number of characters per line.
   Spooler	Name (of file)	A valid file name for the platform, path optional.
   Magnetic Tape	Parameters Rewind?	A valid parameter list for an OPEN command for the device type.
   File Name	Parameters	A valid parameter list for an OPEN command for the device type.

You can use an OPEN command either at the Caché programmer prompt or within an ObjectScript application to open a specific device for reading and writing. When you specify the device, you can use its Device ID or its alias.

Device identifiers you use with %IS or an OPEN command go through up to three levels of interpretation. Thus, if you enter the mnemonic 47 at the %IS global “Device:” prompt, the final device ID that is used may be different. The three levels are described below.

Caché ships with two predefined (default) mnemonic spaces, described in the following table:

The predefined mnemonic spaces are the default mnemonic spaces for:

• Sequential files (^%X364)

• Magnetic Tape (^%XMAG)

• Terminals (^%X364)

• Other devices (^%X364)

These defaults are defined in the Management Portal. Select System, Configuration, Device Settings, IO Settings.

If you create your own mnemonic space routine(s), you may want to change the default mnemonic spaces Caché uses for one or more of the four device types.