Chapter 19 The OLIVETTI Programma 101 desk calculator 239
Fig. 3. Programma 101 keyboard. (Courtesy of Olivetti Underwood Corporation.)
The record program switch (6). When this switch is off, the commands pressed on the keyboard are executed directly. When this switch is on, it directs the computer to store instructions either in the memory from the keyboard or onto a magnetic program card from the memory.
The record program switch must be off to load instructions from a magnetic program card into the memory.
The print program switch (7). When this switch is on (in), it directs the computer to print out the instructions stored in memory from its present location in the program to the next Stop instruction (5), whenever the print key (20) is depressed.
The magnetic program card (8). This is a plastic card with a ferrous oxide backing, used to record programs for external storage. The card is inserted into a magnetic reader/writer (9) to record instructions and/or constants into or from the computer memory. Once inserted, the card may be removed from the computer (10) without disturbing the stored instructions.
(Note: The magnetic-card reader/writer uses only half the magnetic card at a time; consequently, two sets of 120 instructions and/or constants may be stored on a single card.)
The keyboard release key (11). This key reactivates a locked keyboard. If two or more keys are depressed simultaneously, the keyboard will lock to indicate a misoperation. Because the operator does not know what entry was accepted by the computer, after touching the keyboard release key, the clear entry key (16) must be depressed and the complete figure reentered.
Tape advance (12). This advances the printing paper tape.
Tape release lever (13). This enables adjustment when changing tape rolls.
The routine selection (keys V, W, Y, and Z). These keys direct the computer to the proper program or subroutine.
The numeric keyboard (keys 0, 1 , . . . , 9, . , -). This keyboard allows entry of a signed, mixed decimal number. Keyboard entries are automatically stored in the M register.
The clear entry key. This key clears the entire keyboard entry. When keying in the program, a depression of the clear key will erase the last instruction that has been entered into the memory. The printing tape will be spaced.
The start key (5). This key restarts the computer in programmed operation; it is used to code a stop instruction when keying in programs.
The register address (keys A, B, C, D, E, F, and R). These keys identify the corresponding registers. The operating register M has no keyboard identification since the computer automatically relates all instructions to the M register unless otherwise instructed.
The split key (/). This key combined with a register (for example, C/) divides that register into two equal parts. When storage registers are split, the right portion of the split register retains the original designation, and the left side is identified on the tape with the corresponding lowercase letter (for example, C/º c).
The print key ( à ). This key prints the contents of an addressed register.
The clear key (*). This key clears the contents of an addressed register. When the computer is operated manually, a depression of this key will print the number in the register and clear it.
The transfer keys (¯ , , ½ ,). These keys perform transfer operations between the storage registers and the operating registers.
The arithmetic keys (- , +, x, ¸ , Ö ). These keys perform their indicated arithmetic function.
Keyboard and stored-program operations
All the following keys can be used as direct instructions (i.e., manually) if the record program switch is off. Alternatively, if the