Apple II User Manual

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    Z1        ZIABCD (variable name too long)
    TP        TO (variable names cannot be reserved words)
    PSTG$     RGOTO (variable names cannot contain reserved words)
    COUNT
ASSIGNING VARIABLES WITH A LET OR ASSIGNMENT STATEMENT
Besides having values assigned to variables with an input statement, you can also set the value of a
variable with a LET or assignment statement.
Try the following examples:
    A=5
    PRINT A, A*2
    5         10
    LET Z=7
    PRINT Z, Z-A
    7         2
As you will notice from the examples, the "LET" is optional in an assignment statement.
BASIC "remembers" the values that have been assigned to variables using this type of statement.
This "remembering" process uses space in the memory to store the data.
The values of variables are discarded (and the space in memory used to store them is released) when
one of four conditions occur:
*   A new line is typed into the program or an old line is deleted
*   A CLEAR command is typed in
*   A RUN command is typed in
*   NEW is typed in
Another important fact is that if a variable is encountered in a formula before it is assigned a value,
it is automatically assigned the value zero.  Zero is then substituted as the value of the variable in
the
particular formula.  Try the example below:
    PRINT Q;Q+2;Q*2
    0 2 0
RESERVED WORDS
The words used as BASIC statements are "reserved" for this specific purpose.  You cannot use these
words as variable names or inside of any variable name.  For instance, "FEND" would be illegal
because "END" is a reserved word.
Table 206-1 is a list of the reserved words in BASIC.
    Table 206-1.  AIM 65 BASIC Reserved Words
    ABS       FN        LIST      PRINT     SPC
    AND       FOR       LOAD      POS       SQR
    ASC       FRE       LOG       READ      STEP
    ATN       GET       MID$      REM       STOP
    CHR$      GOSUB     NEW       RESTORE   STR$
    CLEAR     GOTO      NEXT      RETURN    TAB
    CONT      IF        NOT       RIGHT$    TAN
    COS       INPUT     NULL      RND       THEN
    DATA      INT       ON        RUN       TO
    DEF       LEFT$     OR        SAVE      USR
    DIM       LEN       PEEK      SGN       VAL
    END       LET       POKE      SIN       WAIT
    EXP