TI-57
The TI-57 is a programmable scientific / engineering calculator from Texas Instruments .
Chronological order
The TI-57 was presented by Texas Instruments on May 24, 1977 at the same time as the two much more powerful pocket calculators TI-58 and TI-59 . It replaced the SR-56 .
There are several successor models TI-57 LCD with a power-saving LC display and non-volatile memory. Ultimately, however, they represent a step backwards, as they are significantly slower and have significantly less memory (49 program steps or 7 data registers).
Technical equipment and functions
The TI-57 has a LED - seven-segment display and a keypad with multiple allocation. The keys have a clear but imprecise pressure point - they tend to bounce . A battery with charger is provided for the power supply.
Storage
The main memory comprises 50 program steps (00-49). Some key sequences (up to 4 keys) can be stored by the computer in a single memory step, which saves space. (Example:) INV 2nd Prd 0.
Numbers can be stored in 8 data registers (0-7). Some of these registers are also used for internal operations, so that they cannot always be used arbitrarily. For example, register t is identical to register 7 and the two registers 5 and 6 are also used for complex operations.
The memory is volatile, i. H. the contents of the program memory and the data register are lost when the computer is switched off. Due to an undocumented function, the computer can be put into a sleep mode that only supplies the memory with power.
programming
The TI-57 is programmed simply by pressing the desired key functions in LRNmode. When the program is executed (start through R/S) the computer processes the recorded list of the keys pressed.
The TI-57 offers e.g. B. a start / stop function, counting loops , conditional jump commands , subprograms that can be nested multiple times , direct addressing of data memories or program steps, simple numeric program labels .
Display in programming mode
The seven-segment display used cannot display letters. In programming mode, the program steps are therefore displayed as a two-digit or three-digit number code in addition to the two-digit program step number. The numeric code corresponds to the row and column position of the key pressed on the keyboard.
The numeric codes "00" to "09" correspond directly to the numeric keys 0to for easier readability 9.
To save program memory is u. a. the code for the second assignment of the keys is used as the numerical value of the key position plus 5. Pressing the 2ndkey therefore does not occupy an additional program step. This INVprovides access to reverse functions and is also placed in the same program step via the minus sign.
To make it easier to read this rather cryptic representation, the computer came with a transparent keyboard overlay with the number codes printed in blue.
Undocumented features
The calculator has some functional undocumented commands. The most useful one enables a battery-saving sleep mode in which the contents of the memory are preserved.
Number format and calculation accuracy
The internal number format is 11 decimal places in exponential representation with 2-digit exponents plus the respective sign . Of these, 8 digits of the mantissa are displayed with a two-digit exponent and the sign, which should make calculation inaccuracies due to rounding errors less noticeable.
Sample program
The following simple program generates a pseudo-random number in the range from 1 to 6.
| step | code | Keys) | function | comment |
|---|---|---|---|---|
| 00 | 30th | 2nd yx | π | Circle number Pi |
| 01 | 75 | + | + | |
| 02 | 33 0 | RCL 0 | RCL 0 | Get the content of register 0 |
| 03 | 85 | = | = | |
| 04 | 35 | yx | y x | |
| 05 | 08 | 8 | 8th | |
| 06 | 65 | − | - | |
| 07 | 49 | 2nd ) | Int | Integer function |
| 08 | 85 | = | = | |
| 09 | 32 0 | STO 0 | STO 0 | Save result in register 0 |
| 10 | 55 | x | x | |
| 11 | 06 | 6 | 6th | Desired upper limit of the random number |
| 12 | 75 | + | + | |
| 13 | 01 | 1 | 1 | |
| 14th | 85 | = | = | |
| 15th | 49 | 2nd ) | Int | Integer function |
| 16 | 81 | R/S | R / S | Stop the program |
| 17th | 71 | RST | RST | Reset (back to step 00) |
Web links
- TI Programmable 57 at the Datamath Calculator Museum
- TI-57 on MyCalcDB (database with calculators from the 1970s and 1980s)
- Programmable Calculators: Texas Instruments TI-57 R / S-Key