By default some Commodore computers boot into uppercase/graphics mode (C64, C128, VIC-20, Plus 4, etc.) while others (PET, CBM etc.) boot into lowercase/uppercase mode. Therefore, depending on machine used, the CHR$(14) may or may not be required to switch into mixed-case mode.
10 print chr$(147);chr$(14);:REM 147=clear screen, 14=switch to lowercase mode
20 print "Hello world!"
30 end