TI-57

The TI- 57 is a programmable scientific / technical calculator from Texas Instruments.

Temporal classification

The TI -57 was introduced at the same time with the two much more powerful calculators TI -58 and TI -59 on May 24, 1977 by Texas Instruments. It replaced the SR- 56th

There are several successor models TI -57 LCD with a power-saving LCD display and a non-volatile memory. Ultimately, however, they represent a step backwards, since they are significantly slower and much less memory have (49 program steps or 7 data register ).

Technical Features and functions

The TI -57 has a Seven-segment LED display and a membrane keyboard with multiple allocation. The keys have a distinct but relatively inaccurate pressure point - they tend to bounce. For the power supply a battery is provided with the charger.

Memory

The RAM is firmly fixed to 50 program steps; this key sequence of up to 4 keys are combined (Example: INV 2nd Prd 0).

Numbers can be stored in 8 data registers. Some of these registers are also used for internal operations so that they can not be used arbitrarily. T is identical to the register 7 and registers the two tabs 5 and 6 are co-used for complex operations.

The memory is volatile, ie the contents of the program memory and the data register is lost when you turn off the computer. Through an undocumented feature of the computer can be put into a sleep mode that supplies only the memory with a current.

Programming

Programming the TI -57 is done by simply pressing the desired key functions in the LRN mode. When you run the program (Start by R / S), the computer processes the recorded list of pressed keys.

For program flow control, the TI -57, for example, a start-stop function, counting loops, conditional jump instructions, multiple, nestable each other subroutines that direct addressing of data storage or program steps, simple numerical program brands (labels ).

Display in programming mode

The seven-segment display used can not display letters. In programming mode, therefore the display of program steps are in addition to the two -digit program step number as a two - or three-digit numeric code. The code number corresponds to the row and column position of the key pressed on the keyboard.

The numeric codes "00" to "09" correspond to the simplified readability directly the numeric keys 0 to 9

In order to save program memory, among other things, the code for the second key assignments used as the numerical value of the key position plus 5. The press on the 2nd button thus does not occupy any additional program step. The Inv provides access to inverse functions, and is also located on the minus sign in the same program step.

To facilitate reading this rather cryptic representation of the computer was a transparent keyboard Auflegefolie with printed in blue at number codes.

Undocumented functions

The computer has some functional undocumented commands. The most useful allows the preservation of the memory even after turning off the computer.

Number format and calculation accuracy

The internal number format is 11 decimal places in exponential notation with 2- digit exponent plus respective sign. Of these 8 digits mantissa are shown with double-digit exponent and sign, thereby increasing computing inaccuracies due to rounding errors are less obvious.

Program Example

The following simple program will generate a pseudo-random number in the range 1 to 6