Synthetic programming (HP-41): Difference between revisions

Revision as of 18:52, 20 September 2023

Revision as of 18:55, 23 September 2023

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'''Synthetic programming''' is an advanced technique for [[Mathematical programming|programming]] the [[HP-41C]] and [[Elektronika B3-34]] [[Programmable calculator|calculators]], involving creating [[Instruction (computer science)|instructions]] (or combinations of instructions and operands) that cannot be obtained using the standard capabilities of the calculator.<ref name="IEEE"/>

Some HP-41C instructions are coded in memory using multiple [[variable-length instruction set|multiple byte]]s. Some of these sequence of bytes correspond to instructions the calculator is able to execute, but these cannot be entered in the program memory using conventional program entry methods (''i.e.'' using the calculator as described in the user's manual.). Synthetic programming uses a [[software bug|bug]] in the calculator firmware to enter those byte sequences as a sequence of other instructions, then partially skipping halfway through the first instruction, so that the calculator believes the end of the first instruction is actually the beginning of a new one. This was called ''byte jumper'' or ''byte grabber''.

It is not clear if the creators behind the HP-41 were aware of all these "black holes". HP did not officially support these techniques, but probably was intrigued by the strange operations and in some cases allowed enthusiasts to practice in their offices and helped to improve it among a whole sense of curiosity.