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LOCATE

Keyword
Abbreviation Token (hex) Version(s) Classification
LOCATE LO{Shift+C} E6 3.5, 7.0 Command and Statement
USING U{Shift+S}  E6  4.7  Preposition

Syntax  
LOCATE { [ + | - ] xVal , [ + | - ] yVal  distance ; angle } ]
 
Parameters Type Legal Value(s) Default Value Note(s)
xVal Integer*  -32768 to +32767  rectangular X ordinate or offset
yVal  Integer*  -32768 to +32767  rectangular Y ordinate or offset
distance Integer*  -32768 to +32767  polar distance
angle Unsigned Integer  0 to 65535  undefined polar angle
 
 
Purpose  
Bitmap graphics state management; set the pixel cursor.

 
 
Remarks  
LOCATE defines the location of the pixel cursor.  The pixel cursor is an internal variable used by many of the BASIC bitmap graphic commands.  Generally the pixel cursor is used to define another point in relative terms (relative to the pixel cursor) or as a default point when a parameter is ommited, in other bitmap commands, functions, and statments.
 
The specified (or calculated, see below) coordinate will be effected by SCALE if it is active.  The resulting values may be off-screen, as long as the values are legal as shown above.
 
A polar coordinate will always be relative to the (old) pixel cursor.  A coordinate specified in rectangular form will normally be an absolute coordinate (independ of the pixel cursor), but using a + or - in front of the xVal or yVal will make that ordinate relative to the (old) pixel cursor.  The x and y ordinates are processed independantly; either, neither, or both ordinates of the rectangular coordinate may be in relative form (whichever use a leading + or -).  Note these must be literal + and - characters in the command/statement.  So if you have a variable X with a negative value (like -10) then it will be used an absolute coordinate unless you preced it with + or - sign.  You normally wouldn't put a - sign unless you want to reverse the direction of the variable.  So, for this example, use +X for a relative ordinate.  As opposed to a variable, if you want to enter a literal negative value (for an absolute ordinate), you must enclose it in parentheses; otherwise it would interpreted as a relative ordinate.  Sorry if that is confusing!  If so, you need to play with relative and absolute coordinates to see clearly what I mean.
 
Unlike the text-mode cursor, the pixel cursor is never visible on screen.  However you may determine the pixel cursor's value with the RDOT function.
 
*Due to a bug in the original C128 ROMs (start-up message says (c)1985), only positive/unsigned values of 0 to 65535 may be used.
 
Any floating-point numbers will first be converted to integers (see INT).  If any value is out-of-range (see above) an ILLEGAL QUANTITY ERROR is generated.
 
Example of absolute rectangular coordinate:
LOCATE 60,60
 
Example of relative rectangular and polar coordinate:
DRAW 1,60,60: LOCATE +10,-10 : REM LOCATE 70,50

READY.
DRAW 1,60,60: LOCATE 20; 30 : REM ~LOCATE 70,43
 
 
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© H2Obsession, 2014
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