CONSOLE TYPEINS

The console contains a keyboard as shown in Figure 9-2. From this keyboard messages can be typed into the store. Typeins are accepted from the console by the executive routine.

Fig ure 9-2. Console Keyboard

The executive routine then routes the message to the proper program by means of a flag character typed in conjunction with the message.

All typeins to programs begin with the character "R". (An exception will be discussed in Section 13 Symbionts). The next character typed in is the flag character. A space is typed next. Then the message is typed.

The program must tell the executive routine what character it wishes to use as its flag. This is done by storing in the label TABB a word with the desired flag character in bits 19 through 24. This operation must be done before the program expects any typeins. Characteristically, if a program expects typeins, one of the first operations to be done in the program is to store its flag in TABB.

At the same time that the flag is delivered to the executive routine, the address of a word in the program is also delivered. This is the address of the typein word. The typein address is delivered in bits one through 15 of the word stored in TABB. The typein word is used by the program to tell the executive routine when it is ready to accept a typein. This is done by storing binary zeros in the type in word. If the typein word contains anything other than binary zeros, the executive routine will not deliver a typed in message to the program even if a message flagged for the program has been received.

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If the type in word contains binary zeros, when the executive routine receives a message flagged for the program, it will do an SL] to the typein address. Consequently, follow ing the typein word of a program should be a short acceptance routine designed to accept the typein. When the ac-ceptance routine receives control, index register one will contain the typein address and index register two will contain the address of the zero word of the area in which the executive rou tine has stored the typed in message. No other index registers will be properly loaded. Consequently, the cover index register for the acceptance routine will be index register one, all index register specifications in the instructions constituting the acceptance routine must be explicit, and only expressions involving binary numbers and reflexive addressing (use of the dollar sign element) ca n appea r in the ope rands of these in s tru ctions. As a c onseq uence, the ac ceptance rou tin e should be designed to do little more than transfer the message from the executive routine typein area to an area in the program and set a connector in the program to indicate that the typein has been received. Control sh ould then be returned to the executive routine by executing a jump with indirect addressing to the typein address. It should be noted that, in doing an SL] to the typein ad,dre ss, the execu ti ve routine ch an ges the contents of the ty pein word to som ethin g other than binary zeros.

When the executive routine transfers control to the acceptance routine, the zero word of the executive routine's typein area will contain I~Rf~, where f is the program's flag. Consequently.

the message the program is looking for actually begins in word one of the executive routine's type in area. Moreove r, before accep ting a typein from the co nsole into the type in area, the executive routine will clear the typein area to all spaces. Consequently, any character positions following the typein in the typein area will contain space symbols. If proper preparation for receiving a message has not been programmed, the message will be lost i.e., no indication of the presence of message is transmitted to the program.

1. Example

A program is designed to execute one of two branches dependent on a typein. If FORCE is typed in, the program is to jump to the label FORCED. If RECHECK is typed in, the program is to jump to the label RECHECK. The typein is requested by typing out TYPEIN.

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A schematic of the UNISERVO IlIA Tape Unit is shown in Figure 9-4. Tape is said to be moving forward when the tape is traveling from the lefthand supply reel to the righthand tape reel, backward when the tape is traveling from the righthand reel to the lefthand reel. The righthand reel is permanent. Consequently, a reel of tape to be read from or written on is mounted on the lefthand hub. The tape is connected to a prethreaded leader fastened to the righthand reel. Because of the prethreaded leader, removal of a reel and the mounting of a new reel takes only about 15 seconds. The reel is removed by pressing the center of the hub.

SUPPLY REEL (QUICK-CHANGE HUB)

TAPE CLAMP TAPE WIPER

VACUUM COLUMN

TAKE UP

---1. _ _ _ - REEL

~-+ ________________ ~r-~~ERASE HEAD

Figure 9-4. Tape Path

VACUUM COLUMN

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If a reel of tape is read or written in a forward direction and is then to be dismounted, it must first be rewound onto the left hand reel. A tape of maximum length is rewound in 125 seconds.

Tape may be written forward, read forward, or read backward. When a block is read backward, the words in each item in the block are stored in the store in the same order as they are stored when the block is read forward.

As many as 16 UNISERVO IlIA Tape Units may be attached to the Processor by a UNISERVO IlIA Synchronizer. The Synchronizer has two channels, one for reading and one for reading or writing. Thus, the Processor can be reading information from one UNISERVO IlIA Tape Unit at the same time it is writing information on another. In addition, transfer of information between the store and the UNISERVO IliA Tape unit is buffered by the Synchronizer. This allows the reading and writing of tapes to occur simultaneously with the use of the store by the Processor to execute ins tructions.

Any number of UNISERVO IlIA Tape Units may be rewound simultaneously. Once rewind on a UNISERVO IlIA Tape Unit is initiated, the Synchronizer is free to control reading, writing, and rewinds on other UNISERVO IlIA Tape Units. The UNISERVO IlIA Tape units are identified by number, the numbers being 0 through 15.

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Although input/output handling is not a programmer responsibility, the user must allocate those areas which will contain the data to be read or written. This function is accomplished by means of the RES directive. Since information must be read and written a block at a time, sufficient area to contain one block must be reserved for each input and output area.

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