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OUT;

For a second example, as the Time Sharing Director bootstraps into action it issues a series of requests for basic

configuration parameters. The following data in FW0 supplies suitable responses without user intervention:

CORE MODULES;8.|

OUT 8 REEL NO;9.|

LEVELS;N.|

DATE D/M/Y;4/5/67.|

TIME ON 24-HOUR CLOCK®HOURS/MINS;1/23.|

This facility had a real equivalent: the Flexowriter had an ‘edge-punched card’ reader. It read data (in paper tape code)

from the edge of a non-standard punched card. Cards prepared with replies to prompts could be inserted into the reader

and read at the maximum rate, thus speeding input and avoiding any delay due to typing errors by the operator.

Note that ee9 requires every Flexowriter input string to be terminated by a RETURN, even when a read-to-End

Message instruction is being obeyed. In reality, KDF9 would end the transfer immediately at the End Message, or when

the required number of characters had been read; but data is not transferred to ee9’s input buffer until a RETURN is

typed. A purely terminating RETURN is discarded from the input buffer by ee9, and is not passed to the KDF9 program.

In response to CTRL-C, ee9 outputs a prompt of its own that lets the diagnostic mode be changed. Replying with a

RETURN (only) causes a FLEX interrupt; when running Director in boot mode, this evokes a ‘TINT;’ prompt.

3.3: READING MORE THAN ONE ROLL OF PAPER TAPE OR DECK OF CARDS

A means is provided to simulate the way in which KDF9’s computer operators could satisfy a program’s demand for data

with several physically-separate rolls of paper tape, loaded into a tape reader in succession. If a program attempts to read

from a tape reader, and the end of the associated file has been reached, ee9 allows the user to specify a successor file to

which the paper tape reader is re-attached. These files are named ‘TRdr’ where d is the device number (0 or 1) and r is a

letter identifying the “roll of tape”. On reaching the end of the current file, ee9 asks for the next letter r; if none is given

the reader is left in the ‘abnormal’ condition and any further attempt to read from it provokes a parity error. Again, it may

be convenient for the files ‘TRdr’ to be realized as links to actual data files with more mnemonic names.

The above also applies, mutatis mutandis, to the punched card reader. Lines of less than 80 characters are padded with

blanks to fill all 80 columns of the card; any line longer than a card is truncated. In ‘direct’ mode, lines may have up to

160 characters, notionally two per column. Any attempt to read a character not in the card set causes a parity error. (The

card punch always generates files suitable as input to the card reader.)

3.4: REPRESENTING THE KDF9 CHARACTER SETS

External data is read and written in the ISO Latin-1 character set, with automatic conversion between Latin-1 and KDF9’s

internal character codes (which are somewhat device-dependent). Several graphic characters in the KDF9 paper tape set

are absent from Latin-1, so a simple transliteration is used to represent them externally. See Appendix 2. The break

character is used for the non-escaping KDF9 underline, so that an Algol 60 reserved word such as ‘real’, seen on KDF9

as ‘real’, appears as ‘_r_e_a_l’, and an underlined End Message, ‘→’, appears as ‘_|’.

In the case of the Flexowriter, tape punches, and tape readers, Case Normal and Case Shift characters are generated on

input, and interpreted on output. This means that when you are typing an input text, it is not necessary to type Case

Normal and Case Shift characters, although it does no harm to do so. When such a text is being read as the input stream

for a two-shift device, an appropriate case-character is generated automatically by the emulator, if the Latin-1 character

being read is not available in the input device’s current shift state. Two-shift devices always start out in the Case Normal

condition. For example, the external Latin-1 string ‘Bill Findlay’ is read into the KDF9 core store as the characters

‘BßILL ñFßINDLAY’, with ß denoting the Case Shift character and ñ denoting the Case Normal character. A KDF9

program that writes the characters ‘BßILL ñFßINDLAY’ to a two-shift device will generate the Latin-1 string

‘Bill Findlay’ as its external representation.

Non-graphic KDF9 characters also have Latin-1 external representations, to enable faithful 1-to-1 conversion between

the internal and external data formats. Apart from the format effectors (Horizontal Tab, New Line, Form Feed), users

should never need to type these characters, as they could not be typed on a Flexowriter.

The format effectors are displayed in tracing output and core dumps using the line printer code, except as follows:

• the KDF9 Tab character is represented by ¬

• the KDF9 Carriage Return character is represented by ®

• the KDF9 Filler, and other non-legible characters, are represented by Ø

Bootable Directors and compiled problem programs are not encoded in Latin-1, but natively, in the KDF9 paper tape

code. They use an 8-bit byte to encode 6 data bits; 8 of these bytes are packed into a 48-bit KDF9 word.

3.5: CHARACTER I/O UNDER WINDOWS

The eccentric behaviour of Windows in relation to text files may cause some problems. Text data input to ee9 may use

CR, LF, or a CRLF pair as the line terminator: ee9 treats all three the same. Textual output from ee9 always uses LF as

the line terminator. Some editors, and other text-processing programs, on Windows may not be able to display it properly.

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MTD 122-250 User Manual Page 3

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