IBM 5150 Manual To Operations page 49

These are program function keys. They are used to make the
system perform the commands listed below:
Key Description
FI "LIST" displays the lines of your program on the
screen.
F2 "RUN" causes your program to begin execution
from the beginning of the program.
!
F3 "LOAD" reads your program from auxiliary storage
e
(e.g., cassette) and stores it in main memory.
~
F4
"SAVE" stores your program on auxiliary storage
(e.g., cassette).
F5 "CONT" restarts your program after you have
interrupted it by a STOP or CTRL BREAK.
F6 "LPTI:" refers to line printer and transfers data
from screen to printer.
F7 "TRON" means trace on and causes the line numbers
of program lines to be displayed as the lines are
executed.
F8
"TROFF" means trace off and cancels command F7.
F9 "KEY" is used to change the function of other
function keys.
FlO "SCREEN" returns program to character mode
from graphics mode and turns off color.
Keyboard 3-3