List of useful Atari BASIC commands

List of useful Atari BASIC commands

Atari specs | ASCII chart | conversions | online emulator

Program Flow

• GOTO [line#] — jump to a new line
• GOSUB [line#] — jump to a subroutine
• RETURN — returns from a subroutine
• ON [##] goto/gosub [line#1],[line#2],[line#3]… — jumps to a line# in the list (1,2,3…)
• IF [expression] THEN [statement]//[GOTO/GOSUB] [line#] — logic check
  • e.g. IF x=5 then y=0 | IF a$=”abcd” then gosub 100
  • operators include: =, >, <, >=, <=, <>, and, or, not
• FOR [variable#] = [##] TO [##] {STEP ##}optional — sets up a loop
• NEXT [variable#] — returns to the top of the loop
  • e.g. for x = 1 to 5 : print x : next x — prints numbers 1 through 5
• END — stops the program
• STOP — stops the program displaying a line# error code | mostly for debugging

Variables

Apple uses two letter variables e.g. STored is the same as STopped
There some 2 letter variables you can NOT use:
AT, FN, GR, IF, ON, OR, TO

• CLEAR — clears all of the variables
• LET [##/$$] = [##/$$] — assigns a value to a number or string
  • e.g. LET x=0 | LET a$=”abc” | can also use: x=0 or a$=”abc”
• DEF FN name=[formula] — sets up the function
  • e.g. DEF FN add(x,y)= x+y
• FN name — calls the function & passes x & y & etc… to it
  • e.g. a= FN add (3,6) — passes 3 & 6 & executes the formula x+y | result is 9

Text

• PRINT [xx,xx$] or [xx+yy] or [aa$+bb$] or [“abc”] {, or ;}optional [more items]
  • at the end of an item use the ; for close spacing or , for wide or nothing for new line
  • e.g. PRINT “x= “; x | PRINT “hello” | PRINT x*2 | PRINT “go “+”home”
• INPUT {[“description”;] optional} [xx1,xx1$], [xx2,xx2$], etc…
  • e.g. INPUT x,y | INPUT “name=”; aa$
• GET [xx,xx$] — waits for a single key-press & sets it to the variable
  • note: a numeric value (X vs X$) you will get an error if you don’t press a # key
• HOME — clears the screen [some BASIC’s use CLS or CLEAR]
• HTAB / VTAB [xx] — moves the cursor horizontally or vertically
• FLASH — starts flashing text
• INVERSE — starts inverse text
• NORMAL — resets to normal text

Data Arrays

• DIM name/name$,{more can be added}
  • e.g. DIM aa$(15) | 2 dimensional array= DIM xx(5,5) | 3D= DIM xx$(5,5,5)
• DATA [xx,xx$],[xx2,xx2$],etc…
  • sets up the data for variables | can be numbers or text
  • no spaces between commas, quotes around text is not necessary
• READ variable — loads data into variable (number) e.g. READ x$(2)
• RESTORE — resets to the first variable in the list i.e. x$(1)

String/Conversion Functions

• LEN(xx$ or “abc”) — outputs the length (# of characters) of a string
• LEFT$(xx$ or “abc”],[x) — same, but left characters up to x
• RIGHT$(xx$ or “abc”],[x) — same, but right characters back to x
• MID$(xx$ or “abc”],[x],[y) — middle chars starting at x to length y
  • e.g. print mid$(“testing”,2,3) outputs: est
• ASC(xx$) — gives the ASCII value of first character in xx$
• CHR$(xx) — gives the character of ASCII # xx
• STR$(xx) — converts numbers into strings
• VAL(xx$) — converts numeric strings into numbers | stops if it hits a letter
  • e.g. ASC(“f”) outputs: 102 | CHR$(102) outputs f | VAL(“123a45”) outputs: 123

Math Functions

= , > , < , >= , <= , <>
equal,greater,less,greater or equal,lesser or equal, not equal
, – , * , / , ^
add,subtract,multiple,divide,power
AND , OR , NOT — boolean operators
note the plus(+) sign can be used to put strings together e.g. a$= “ab”+”cd”

• ABS (xx) — absolute value of xx, always positive
• ATN (xx) — arc-tangent of xx
• COS (xx) — cosine of xx
• EXP (xx) — raise e to xx | e is Euler’s Number = 2.71828
• INT (xx) — integer part of xx, gets rid of decimals
• LOG (xx) — natural log of xx
• RND (xx) — generates a random number between 0 and 1
• SGN (xx) — sign of xx : -1 for neg #, 0 for zero, 1 for positive #
• SIN (xx) — sine of xx
• SQR (xx) — square root of xx
• TAN (xx) — tangent of xx

Miscellaneous

• REM [comments] — treats all text after it as a comment (not executable)
• TRACE / NOTRACE — shows/hides line numbers while running | used for debugging
• ONERR GOTO [line number] — sends program to a line# if an error occurs
• RESUME — tries the line that caused an error again (similar to gosub/return)

Atari | ASCII table | Converting

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