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A custom tape image is a plain-text file that starts with a VFU definition line and then contains one channel-
definition line for each line of the form. The number of channel-definition lines establishes the form length.
A semicolon appearing anywhere on a line begins a comment, and the semicolon and all following characters are
ignored. Zero-length lines, including lines beginning with a semicolon, are ignored. Note that a line containing one
or more blanks is not a zero-length line, so, for example, the line “
; a comment starting in column 2
” is not ignored.
The first (non-ignored) line in the file must be a VFU definition line of this exact form:
VFU=<punch characters>,<no-punch character>{,<title>}
...where:
•
punch characters
is a set of one or more characters used interchangeably to represent a punched
location.
•
no-punch character
is a single character representing a non-punched location.
•
title
is an optional description that is printed by the
SHOW LPT VFU
command; the description “Custom
VFU” is used if the title is omitted.
If the
VFU
line is missing or not of the correct form, then
Format error
is displayed on the simulation console, and
the VFU tape is not changed.
The remaining lines define the channels punched for each line of the printed form. The line format consists of a
sequence of punch, no-punch, and “other” characters, in channel order. Each punch or no-punch character defines
a channel state, starting with channel 1 and proceeding left-to-right until all channels for the VFU are defined; any
the extra channel states on the line are ignored. If the line terminates before all channels are defined, the
remaining channels are set to the no-punch state. Any "other" characters, i.e., neither punch characters nor no-
punch characters, are ignored and may be used freely to delineate the tape channels.
For a standard 66-line form, the first printable line (form line 1) is paper line 4, and the last printable line (form line
60) is paper line 63. The first channel-definition line in the file specifies form line 1, i.e., the top of the form, and
must have a punch in channel 1. Channel line 60 defines form line 60, i.e., the bottom of the form. Six more
channel lines follow: three for the bottom margin, and three for the top margin of the next form.
