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Table of Contents
This chapter describes the following topics which relate to input and output processing:
Input/Output Intrinsic Special Variables, and their Maintenance.
GT.M provides several intrinsic special variables that allow processes to examine, and in some cases change, certain aspects of the input/output (I/O) processing. The focus in this chapter is how GT.M handles the standard ones, such as $IO, $X, $Y, and those that are GT.M-specific (for example, $ZA, $ZB).
Each device type supported by GT.M responds to a particular subset of deviceparameters, while ignoring others. Devices may be programmed in a device-specific manner, or in a device-independent manner. This chapter discusses each device type, and provides tables of their deviceparameters.
Input/Output Commands and their Deviceparameters
GT.M bases its I/O processing on a simple character stream model. GT.M does not use any pre-declared formats. This chapter describes the GT.M I/O commands OPEN, USE, READ, WRITE, and CLOSE.
OPEN, USE, and CLOSE commands accept deviceparameters, which are keywords that permit a GT.M program to control the device state. Some deviceparameters require arguments. The current ANSI standard for GT.M does not define the deviceparameters for all devices. This chapter includes descriptions of the GT.M deviceparameters in the sections describing each command.
The term "device" can refer to an entity manipulated by application code using Open, Use, Close, Read and Write commands as well as a device from the perspective of the operating system. We endeavor herein to always make it clear from the context which meaning is intended.