RPL

RPL is a stack-based programming language designed for programmable calculators, mainly used in Hewlett-Packard handheld devices. It is known for its simplicity and efficient execution of mathematical calculations.

Hello, world code example:

TITLE Goodbye World;

LET NL=10;

EXT PROC(REF ARRAY BYTE) TWRT;

ENT PROC INT RRJOB();

    TWRT("Hello world!#NL#");
    RETURN(1);

ENDPROC;

Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.

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