TI-57

The TI-57 is a discontinued product line of programmable calculators made by Texas Instruments between 1977 and 1982. There are three devices by this name made by TI. The first TI-57 devices with LED displays were released in September 1977 along the more powerful TI-58 and TI-59. The original devices have 50 program steps and eight memory registers. Two later versions named TI-57 LCD and TI-57 LCD-II have LCDs, but are less powerful and have much less memory: 48 bytes to be allocated between program 'steps' and storage registers.
The TI-57 lacks non-volatile memory, so any programs entered are lost when the calculator is switched off or the battery runs out.
The LED display version of the TI-57 was sold with a rechargeable nickel–cadmium battery pack BP7 containing two AA size batteries and electronics to raise the voltage to the 9V required by the calculator. A popular modification is to power it from a 9V battery and use the battery cover of a LED TI-30 or a part of the dismantled battery pack. This modification provides a better battery life than the original battery pack.
Included, with at least the original version, was a book entitled Making Tracks Into Programming. It is subtitled "A step-by-step learning guide to the power, ease and fun of using your TI Programmable 57".
Radio Shack also marketed this calculator, rebranded as the EC-4000.

Programming

The programming capabilities of the TI-57 are similar to a primitive macro assembler.
Any keystroke can be stored, along with some simple program flow control commands and conditional tests. These include:
GTO : Causes program pointer to jump immediately to a Label or to a specific program step.
SBR : Causes a program to jump to a Label, and on encountering an Inv SBR command, continue executing at the instruction immediately following the original SBR.
DSZ : Decrements storage register zero, and skips the next instruction if the result is zero. There was also an inverse form, Decrement and Skip if Not Zero.
Tests for equality/inequality can be performed against a value on the display and a dedicated test register, t. The result of the test causes the next instruction to be conditionally skipped.
Programs can be edited by inserting, deleting, or overwriting a program step.
A NOP function is provided to allow a program step to be ignored.
Due to the hard limit of 50 program steps, use of NOP is infrequent.
The TI-57 uses the "one step, one instruction" principle, regardless of whether one instruction required one or up to four keypresses.

Sample program

The following program generates pseudo-random numbers within the range of 1 to 6.

Step	Code	Key	Function	Comment
00	30		π	Pi
01	75		+
02	33 0		RCL 0	Recall register 0
03	85		=
04	35		y^x
05	08		8
06	65		−
07	49		Int	Integer function
08	85		=
09	32 0		STO 0	Store result in register 0
10	55		x
11	06		6	Upper bound of the random number
12	75		+
13	01		1
14	85		=
15	49		Int	Integer function
16	81		R/S	Stop
17	71		RST	Reset