Each graphics protocol command consists of an operator and, optionally, one or more operands.
Operator: An operator defines the function of the command (for example, a command to draw a circle.) It consists of one or two uppercase alphabetical characters.
Operand: The operand defines the limits of the operator (for example, the radius of a circle). It consists of a series of characters representing a signed or unsigned integer, or a character string. An operand is delimited by a valid delimiter, another operator, an invalid operand, or an ETX character.
The number and type of operands allowed vary for each command. A null operand (consecutive delimiters) is valid and is considered to have a value of zero.
The delimiter between numeric operands is a comma (x,y); the delimiters for text are single quotation marks ('text'.)
The valid operands and types are listed below:
|
Valid Operand |
Type |
|---|---|
|
Absolute coordinate (x or y) |
Unsigned integer |
|
Relative coordinate (x or y) |
Signed integer |
|
Radius (r) |
Unsigned integer |
|
Angle (sa or ea) |
Signed integer-Modulus 360 |
|
Attribute |
Unsigned integer |
|
Text string |
Character string |
|
Control |
Unsigned integer |