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Left Hand Pointer

$IO

M[UMPS] by Example

Right Hand Pointer

Introduced in the 1977 ANSI M[UMPS] language standard.

The value of this variable identifies the current input/output device.

New %IO Set %IO=$IO
Use OTHERDEV
Do ANYTHING
Use %IO

would make it possible to stack the usage of a device-specifier.

Note that common practice like:
For ... Use ONEDEV Do SUB1 Use OTHERDEV Do SUB2 ...
is a situation where stacking of device-specifiers makes little or no sense.

Approved for addition in a future M[UMPS] Language Standard.

The initial value of $IO is equal to the value of $Principal if the implementation executes implicit Open and Use commands while creating a job, so that the initial current device is indeed the device identified by the value of $Principal. Otherwise, the initial value of $IO is the empty string.

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Copyright © Standard Documents; 1977-2017 MUMPS Development Committee;
Copyright © Examples: 1995-2017 Ed de Moel;
Copyright © Annotations: 2003-2017 Jacquard Systems Research.

The information in this page is NOT authoritative and subject to be modified at any moment.
Please consult the appropriate (draft) language standard for an authoritative definition.

Some specifications are "approved for inclusion in a future standard". Note that the MUMPS Development Committee cannot guarantee that such future standards will indeed be published.

This page most recently updated on 13-Sep-2014, 07:20:51 .

For comments, contact Ed de Moel (demoel@jacquardsystems.com)