SQR(<numeric expression>)
Returns the square root of <numeric expression>.  An error message
will result if <numeric expression> evaluates to a negative number.
Examples:  SQR(B*B-4*A*C)    SQR(2)    SQR(X)

STR$(<numeric expression>)
Returns the string representation of <numeric expression>,
without leading or trailing spaces.
Examples:  STR$(3052.67)    STR$(NUMBER)    STR$(X*Y/Z)

TAB(<numeric expression>)
Spaces to column <numeric expression> on the PRINT device.
If tabbed column is less than the present position, the next
output from PRINT will go on the next line in the correct
position.
Examples:  TAB(20)    TAB(30)    TAB(N*2)    TAB(POSITION)

TAN(<numeric expression>)
Returns the tangent of angle <numeric expression>, which is in radians.
Examples:  TAN(DEGREES*3.14/180)    TAN(.25)    TAN(X^2/Y)

USR(<expression>)
Calls a user (machine language) subroutine at the address in
location USER.  The address of location USER is in the 11th
and 12th bytes after the start of BASIC (see appendix C).
The <numeric expression> is evaluated and placed in registers
D&E.  The USR function returns with the value that is returned
in registers D&E.  For example, if the machine language subroutine
decremented D&E by 5, the value of the USR function would be 5
less than it's argument.  Of course, anything may be done in a
USR subroutine, but it is recommended that all registers that
are changed besides D&E should be saved and restored on a stack.
Example:   USR(0)   USR(N)   USR(N*M)   USR(ARG)

VAL(<string expression>)
Returns the numerical value of the string <string expression>.
Leading spaces are ignored.  If the string expression is not a
valid number, zero is returned.
Examples:  VAL(FIELD4$)    VAL(COST$)    VAL(A$)    VAL("3.14")





IMPORTANT NOTE:
Functions are never to be used by themselves, but only
where variables, constants, and expressions can be used.
For example:  CALL(PLOT,X) would be incorrect,
whereas       LET Y=CALL(PLOT,X) would be correct, even
though Y was not used for anything else.  This is because
the CALL function, like other functions, returns a value
which must be assigned to something, in this case, Y.







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