Examples of using PRINT:

PRINT "TEXT",                   TEXT followed by a tab
PRINT "TEXT";"ABC"              Concatenated strings: TEXTABC
PRINT "TEXT":PRINT "ABC"        Two instructions in the same line
PRINT                           New line

The Atari disk input/output commands:

• OPEN #num, code, 0, file
• CLOSE #num
• PRINT #num
• INPUT #num

Example:

DIM F$(20)
F$="H1:TEST.DAT"
 
OPEN #1,8,0,F$                          Open a file TEST.DAT for writing
PRINT #1;"HELLO!"                       Write a string to the file
PRINT #1; 123.4                         Write a number (as a string) to the file
PRINT #1;"THERE IS MORE:"; 987          Write a string and a number (as a string) to the file
CLOSE #1                                Flush the buffer and close the file
 
OPEN #2,4,0,F$                          Open a file TEST.DAT for writing
REM                                     Note that we could use #1 again as the file has been closed
DIM D$(30):REM                          Allocate memory for a string we want to read from the file
INPUT #2,D$                             Read the string to the variable D$
PRINT D$:REM                            Prints HELLO!
INPUT #2,D$:REM                         Read the next string (which is a number stored as a string)
PRINT D$:REM                            Prints 123.4

More on using disks with Atari BASIC can be found here.

• ^ - Control key
• ! - Shift key

• Delete a line by typing its number.
• Stop the LIST instruction: Control + 1
• Display a graphical symbol: Control + key
• Switch to graphical symbols mode: Control + Caps
• Insert a space: Control + Insert
• Insert a line above the current line: Shift + Insert
• Delete the current line: Shift + Delete
• Arrows: Control + arrow key