The 5100 keyboard (Figure 2) has alphameric and numeric keys. The alphameric
keys are grouped together and are similar to those on a typewriter keyboard.
When the keys are pressed, the characters entered appear in the input line (one
of the bottom two lines) on the display screen. If either shift key is pressed and
held, the upper symbol on the key pressed is entered. The top row of alphameric
keys ban be used to enter numbers; however, numbers can be conveniently en-
tered using the numeric keys on the right side of the keyboard. The arithmetic
symbols (+ - f x) located on the top row of the alphameric keyboard can also
be entered using keys to the right of the numeric keys.
The keyboard contains some keys that perform operations in addition to those
performed by a typewriter. These keys are discussed in the following text. Uses
of the APL language symbols on the keyboard are discussed in the APL language
chaptier (Chapter 4) of this manual.
Pressihg ATTN (attention) when entering information from the keyboard erases
everything from the cursor to the end of line 0.
Pressing ATTN during execution of any expression or user-defined function stops
system operation at the end of the statement currently being processed. To re-
start the execution of a user-defined function, enter -toLC.
Output that was being generated before the system operation stopped may not be
displayed because there is a delay between the execution of the statement that
causes the output and the actual display of the output.
When ATTN is pressed twice during the execution of a statement (either inside
or outside a user-defined function), the execution of that statement stops im-
medidtely. Also, the message INTERRUPT, the statement, and a caret (A) that
indicates where the statement was interrupted are displayed.
When pressed once, HOLD causes all processing to stop; when pressed again, it
allows processing to resume. The primary purpose of HOLD is to permit reading
the display information during an output operation, when the display is changing
rapidlb. When the hold is in effect (HOLD pressed once), only the COPY DISPLAY
key is active.
1. Holding down the CMD key and pressing HOLD is restricted to use by the
service personnel.
2. When the hold is in effect (HOLD pressed once), the use of the arithmetic
keys (+ - f x) on the right side of the keyboard are restricted to use by
service personnel.
When this key is pressed, the input line of information on the display screen is
processed by the system. This key must be
pressed for any input to be processed.
When this key is pressed and held, pressing an alphameric key in the top row
causes the APL command keyword or character above that key to be entered
in the input line. The command keywords are: )LOAD, )SAVE, ICONT, )LIB,.
Note: Holding down the CMD key and pressing HOLD is restricted to use by the
service personnel.
Positioning the Cursor and Information on the Display Screen
The following keys are used to position the cursor and information on the display
Forward Space
When this key is pressed once, the cursor moves one position to the right. When
this key is held down, the cursor continues to move to the right. When the cursor
reaches the last position on one input line (line 1 or 0), it wraps around to the
first position on the other input line.
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