If a function is executed in a program, execution of RTN resumes the program.   A function executed from the keyboard or a nonfunction program can execute another function. The latter, however, cannot properly execute yet another function. Note that: 1. LBL can prefix a digit as well as a top row key, thus allowing up to 15 unique labels. We shall presently use a digit label in a program that repeats. 2. RTN can be used if pressed manually to move the program pointer to the top of memory. We shall use this to start execution at the very first step in program memory. 3. If a program calls another programmed function, the RTN terminating the function does not cause a stop, but rather resumes the sequential execution of the calling program.