Texas Instruments 990 Operation Manual page 116

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The Up (U) command is used to move the pointer up a specified number of lines. The Top (T)
command moves the pointer to the top (first line) of the buffer. The Bottom (B) command
moves the pointer to the bottom (last line) of the buffer.
The pointer commands permit the user to move the pointer as desired for effective use of
commands that identify lines by specifying the displacement from the pointer.
4.4.3 MOVING LINES TO OR FROM BUFFER. PX9EDT allows the user to edit data in a
buffer and identifies lines of data in the buffer with line numbers or with a pointer.
Source lines or object records are placed in the buffer for editing by PX9EDT by reading lines
from the input file or by entering lines at the keyboard. The Down (D) command is used to read
lines from the input file and move them to the buffer. The Insert
(1)
and Change (C) commands
are used to enter lines from the keyboard. When data is read from the input file, PX9EDT
assigns a line number to each line or record. The line number mayor may not be printed, but it
is not written on the output file. When lines of data are moved in the buffer, each line retains its
line number. When lines are removed from the buffer, the line numbers are not reassigned. No
line numbers are assigned to lines of data that are entered at the keyboard.
After data has been edited, the buffer may contain lines without line numbers, and the lines in
the buffer are not necessarily in line number sequence. When a line has a line number, the line
may be specified by line number. Any line may be specified by a displacement from the pointer.
Only data in the buffer may be edited; therefore, it may be necessary to move data from the
buffer to the output file to leave more space in the buffer so that additional
line~
may be read
from the input file or entered from the keyboard.
The Keep (K) command writes a specified number of lines from the buffer to the output file.
The number of lines specified by the Keep command is written from the top of the buffer
regardless of the location of the pointer line. If a number is not specified, all lines in the buffer
are written to the output file. This makes these lines unavailable for further editing in this
session.
The Quit (Q) command writes lines from the buffer and input file followed by an end-of-file
record, and terminates PX9EDT. The Quit command may write lines from the buffer and input
file, or from the buffer only. Quit should be used as the final command in an edit session so
that an end of file will be written to the output file.
4.4.4 HANDLING OF FILE DATA FORMATS. The following special characters are recognized
by the text editor I/O routines. A backspace character (CTRL H) backspaces one character
position. A RUB OUT character deletes the current input line. A tab (CTRL
I)
echoes as one
space upon character input, but moves to the nearest tab stop when the line is printed. Tab
stops are defined at character positions 8, 13, 31, and 33. An escape (ESC) entered from the
keyboard during cassette or print output causes the current I/O operation and the command to
be aborted. Control returns to the command handler, and another command may be entered
when a "?" is printed.
All other characters from keyboard input, printer output, and cassette read and write are
handled as specified in Appendix C.
4-4
Digital Systems Division .