The PROC processor uses four variable length I/O buffers—a primary and secondary input buffer and a primary and secondary output buffer. These buffers are the stack. Basically, the function of a Proc is to move data from the input buffers to the output buffers. At any time, one of the input buffers is considered active, and so is one of the output buffers. Buffers are selected as active by certain Proc commands.
The primary input buffer contains the Proc name and optional arguments, if any. The primary output buffer is used to build the command that ultimately is submitted to TCL for processing. The secondary input buffer contains data subsequently entered by the user in response to an IN command. Usually, the data in this buffer is tested before it is transferred to the secondary output buffer. When all data has been moved to the secondary output buffer, control is passed to the primary output buffer via a P or a PP command. The command that resides in the primary output buffer is executed at the TCL level. The data in the secondary output buffer, if any, is used to feed other processors, such as AQL or the Update Processor. When the process is finished, control returns to the Proc and new data can be moved to the output buffers.
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