Page:CTSS programmer's guide.djvu/32

 mapping tables (Figure 3.1) for both the 6-bit and 12-bit character codes. (The high order 6 bits will be referred to as logical case bits.) In addition each console has a particular quit signal technique. All characters are interpreted individually; hence any combination of legal characters may be used in a message. In particular, the physical case is automatically kept track of on both input and output, so that the user need not program physical case shifts.

In the case of 6-bit normal BCD mode input, characters which do not map into normal BCD characters or functions are enclosed in parentheses on the following chart and are ignored on input. The 6-bit normal BCD mapping is obtained by deleting the 6 high-order case bits. In a l2-bit mode input, all characters are coded and kept in a message.

In the case of console output, in the 6-bit normal BCD mode, logical case 0 will be used, while in the full 12-bit mode, all characters will be printed as specified with unused codes being ignored. After all output messages, the console physical case will be restored to its previous case before output, except for the IBM 1014 and 1050 Selectric typewriter consoles, where lower case will be restored after output.

When using Model 28 Teletype consoles, the quit signal is generated by depressing and relasing the break key. There are no backspace or color shift functions available.

When using the IBM 1014 Selectric typewriter consoles, the quit signal is generated by the sequence of: inquiry request, "#," inquiry release. To initiate each line of input, the inquiry request key must be depressed. If the check light comes on from typing too fast, inquiry cancel must be given and the line reinitiated. Inquiry release acts as a carriage return signal. The color shift function automatically reverses between input and output and is not codable. The only break character possible is carriage return. Type balls may be changed by a  command. It is not possible to input a non-printing message, hence when it is desired to issue a carriage return with no message, the character "π," which is always ignored, is issued before the carriage return.

When using the Flexowriter consoles, the quit signal is generated, 18