GEINOS - I/O request.

Usage:

mme     geinos
operation_word_1
identification_word_1
operation_word_2         -- sometimes omitted
identification_word_2    -- sometimes omitted
return_word

Where:

operation_word_1

indicates the I/O operation to be performed.

identification_word_1

points to a file control word that identifies the file on which the I/O operation is to take place. If the file control word is invalid, MME GEINOS will abort the user program. Bits 18-19 of the file code word can contain:

00: indicates a normal MME GEINOS request.
01: indicates that a Relinquish Control (MME GERELC) operation should immediately follow the MME GEINOS on the file.
10: indicates that a Roadblock (MME GEROAD) should be performed as part of the MME GEINOS operation.

operation_word_2 identification_word_2

are present in I/O requests where two related operations must be performed sequentially (e.g. SEEK/READ, SEEK/WRITE).

Description:

MME GEINOS issues an I/O request. It will abort the program if the request is found to be invalid. Otherwise, it may:

postpone acceptance of the request if the request queue is already in use;
queue the request (which initiates the I/O action immediately if the channel and device are not busy);
erase all data from the point at which the tape is positioned when the erase-to-end-of-tape command is received.