Atari BASIC included the "ENTER" keyword, which was the "opposite of" LIST. Whereas LIST wrote a program to text, ENTER read a program from text. One could use ENTER to read libraries by adding those lines to an existing program.

Atari BASIC included the "ENTER" keyword, which was the "opposite of" LIST. Whereas LIST wrote a program to text, ENTER read a program from text. One could use ENTER to read libraries by adding those lines to an existing program.

In contrast to most BASICs, Atari BASIC did not have any limitations between which keywords would operate in interactive mode vs. program mode. Thus:

1 L. 

Would cause the program to output itself when run. Likewise, you could use the ENTER in the program to have the program load more code and add it to itself.