1.3 Language Elements

1.3.1 Character set

• The Universal Coded Character Set (UCS) includes all other character sets. It guarantees bi-directional compatibility with other character sets, i.e., if user converts any text string to UCS format and then back to the original encoding, the user does not lose any information.The UCS contains all the characters of known languages.
• According to the national standard GB/T15969.3-2005, the text elements in the text and graphic programming language used by programmable controllers should be composed of 3-7 columns of characters according to the “Basic Code Table” in the programmable controllers and expressed as Chinese characters according to the “Basic Set of Chinese Character Set for Editing Characters for Information Exchange” in the standard GB2312-1980.
• Except for comments, string literals, and string variable values, uppercase and lowercase letters have the same meaning. For example, Control and CONTROL are the same variable name or identifier.

1.3.2 Identifier

• Identifier : A string of letters, numbers, and underscore characters, starting with a letter or underscore character. However, trailing underscores are not allowed, and the font and case of letters in identifiers have no meaning. At the same time, identifiers are not allowed to start with multiple underscores or multiple embedded consecutive underscores. In Baosky PLC namespaces, variables, GVS, PU, FB,FC, etc. follow this specification.
• Identifiers are used to name various variables, programs, configurations, resources, etc.

Serial number	Feature description	Example
1	Uppercase letters and numbers	W4; ER8; RT8
2	Uppercase and lowercase letters, numbers, embedded underscores	Var2; Var2_int; Var2_int_9; var1,var_int
3	Uppercase and lowercase letters, numbers, leading or embedded underscores	_Var2; _12_int

1.3.3 Comments

• Improve code readability: Comments can help other developers better understand the logic and intent of the code, saving time reading the code.

• Convenient code maintenance: As the project iterates, the code may be changed and fixed. Good comments can help developers locate problems and make modifications more easily.

• Comment related instructions are shown in the table below:

Comment description	Example
Single line comment //...	x:=12; //Assign the value of variable x to 12
Multi-line comments (*....*)	(*a:=10; b:=true;*) Comment two lines of code
Multi-line comments /*....*/	/*a:=10; b:=true;*/ Comment two lines of code
Nested comments use (*..(*..*)..*)	(*(*b:=true;*)*) Nested comments
Nested comments use /*../*..*/..*/	/*/*b:=true;*/*/ Nested comments

1.3.4 Literal (constant)

• Literal: A literal is a value that represents the value of some constant. There are three types: numeric literal, string literal, and time literal. In computer science, a literal is a notation used to express a fixed value in source code.
• Numeric literal: defined as a decimal number or base number. In a given implementation, the maximum number of bits for each numeric literal is sufficient to represent the entire range of values ​​of all data types represented by the literal.
• Numeric literals are divided into two categories: integer literals and real number literals. The base of integer literals is decimal, and can also be expressed in base 2 or 16. For integer literals with base 16, use the extended set of digits A through F, which represent decimal 10 through 15. The base number should not contain the prefix "+" or "-". They are interpreted as bit string literals. Real numerical values ​​are distinguished by the presence of a decimal point.
• The characteristics and examples of digital direct quantities are as follows

Serial number	Description	Example	Explanation
1	Integer literal	-12 123_4 +986	123_4 is equal to 1234
2	Real literal	0.0 0.369 3.141592_6	3.1415926 is equal to 3.141592_6
3	Real literal expansion	-1.34E-12,-1.34e-12 1.0E+6,1.0e+6 1.334E6,1.334e6	e (E) is not case sensitive + can be omitted
4	Binary literal	2#1111_1111 2#1110_0000	Binary all 1, represents decimal 255 Binary 111 represents decimal 224
5	Hexadecimal literal	16#FF or 16#ff 16#E0 or 16#e0	Hexadecimal FF represents decimal 255 Hexadecimal E0 represents decimal 224
6	Boolean 0 or 1	Number 0 or 1
7	Boolean true or false	TRUE FALSE
8	Type literal	INT#-12 WORD#16#AFF WORD#1234 1234=16#4D2 UINT#16#89AF CHAR #'A' BOOL#0 BOOL#1 BOOL#FALSE BOOL#TRUE

• String literal

  • Single byte: Occupying one byte, a single-byte string literal is a sequence of zero or more characters, beginning or ending with a single quote character. In a single-byte string, the three-character combination of the dollar sign followed by two hexadecimal digits can be understood as the hexadecimal representation of the 8-bit character code.
  • Single-byte string literals are shown in the following table:

  Serial number	Description	Example
  1	Null (zero length)	''
  2	Char	'a'
  3	Space	' '
  4	Single quotes	'$''
  5	Dollar	'$$'
  7	Line break, input line	'$L' or '$l'
  8	New line	'$N' or '$n'
  9	Page change, input page	'$P' or '$p'
  10	Enter	'$R' or '$r'
  11	TAB key	'$T' or '$t'
  12	Supports single byte with $ character and two hexadecimal characters	'$0A'
  13	String	STRING#'OK'
  14	Character	CHAR#'X'

• Time literal

• Duration data shall be defined by the keywords T#, TIME#, or LTIME# on the left. Duration data shall support representation by days, hours, minutes, seconds and milliseconds (LTIME# supports nanoseconds), and any combination thereof, with units permitted to be separated by an underscore character, and units of time such as seconds, milliseconds, etc., may be represented by uppercase or lowercase letters.

• The inherent elements of time direct literal are shown in the following table:

Serial number	Description	Example
1	d	days
2	h	hours
3	m	minutes
4	s	seconds
5	ms	milliseconds
6	us	microseconds
7	ns	nanoseconds

• The common expressions of time literal length and short prefixes are as shown in the following table:

Serial number	Description	Example
1	Short prefix	T#14ms T#-14ms LT#14.7s T#14.7m T#14.7h t#14.7d t#25h15m t#5d14h12m18s35ms lt#12h4m34ms230us400ns
2	Short prefix (units separated by underscore character)	t#25h_15m t#5d_14h_12m_18s_35ms
3	Long prefix	TIME#14msTIME#-14ms time#14.7s LTIME#5m30s500ms100.1us
4	Long prefix (units are separated by underscore characters)	TIME#25h_15m ltime#5d_14h_12m_18s_3.5ms LTIME#34s_345ns

• The common expressions of the literal length and short prefixes of time and date are as shown in the following table:

Serial number	Description	Example
1	Date (long prefix)	DATE#1984-06-25 date#2010-09-22
2	Date (short prefix)	D#1984-06-25
3	Time (long prefix)	TIME_OF_DAY#12:36:45.32
4	Time (short prefix)	TOD#15:15:15.36
5	Time and date (long prefix)	DATE_AND_TIME#1956-03-14-12:56:22
6	Time and date (short prefix)	DT#2021-03-25-14:56:23

warning

Only the smallest unit does not support floating point numbers

1.3.5 Keywords

• A keyword is a combination of offset characters that is used as a separate syntax element.

• Includes: basic data types, language elements, etc.

• Keywords are shown in the table below:

Serial number	Description	Keywords
1	BOOL	BOOL
2	Byte	BYTE
3	Word
4	Double word	DWORD
5	Long word	LWORD
6	Short integer type	SINT
7	Unsigned integer type	UINT
8	Integer type	INT
9	Unsigned integer type	UINT
10	Double Integer	DINT
11	Unsigned double	UDINT
12	Long Integer	LINT
13	Unsigned long	ULINT
14	real number	REAL
15	Long real number	LREAL
16	single-byte character	CHAR
17	String	STRING
20	Duration (ms)	TIME
21	Date	DATE
22	Day and time	TIME_OF_DAY
23	Date and time	TOD
24	Date and time	DATE_AND_TIME
25	Date and time	DT
26	Long time	LTIME
32	User-defined type	TYPE
33	Type end definition	END_TYPE
34	Array	ARRAY ARRAY
35	Array or CASE statement OF	OF
58	Logical true	TRUE
59	Logical false	FALSE
60	Start of variable segment within GVS	GLOBAL VARIABLE
61	Start of variable segment in PU	VAR
62	Start of temporary variable segment in PU	TEMP
63	Start of input variable section	INPUT
64	Start of output variable section	OUTPUT
65	Start of input and output variable section	INOUT
66	Start of variable segment within GVS	GLOBAL CONSTANT
67	Constant	LOCAL CONSTANT
68	Save variables after power off	RETAIN
69	Negate (find the complement code)	NOT
70	Modulo operation (representing the remainder when a is divided by b)	MOD
71	"AND" operation	AND
72	"XOR" operation	XOR
73	"OR" operation	OR
74	IF instruction	IF
75	Instruction part of the IF instruction	THEN
76	Selection conditions of IF instruction	ELSIF
77	Alternative branches in IF and CASE statements	ELSE
78	End IF instruction	END_IF
79	Introduction of CASE statement	CASE
80	End CASE statement	END_CASE
81	Introducing the FOR statement	FOR
82	Define the entire range of values ​​for the FOR statement	TO
83	FOR loop increment	BY
84	Introducing the directive section in the FOR and WHILE directives	DO
85	End FOR statement	END_FOR
86	Introduction of REPEAT	statement REPEAT
87	End REPEAT	Instruction part of statement UNTIL
88	End REPEAT statement	END_REPEAT
89	Introduction of WHILE instruction	WHILE
90	End WHILE command	END_WHILE
91	Terminate the current program channel in the loop and enter the next loop	CONTINUE
92	Instruction to exit the loop	EXIT
93	Introduction of GOTO statement	GOTO
94	Exit this program unit	RETURN

1.3.6 Delimiter

• Delimiters are used in “instructions” or statements to isolate, identify, etc. Commas are used to separate multiple variables; semicolons indicate the end of a one-day statement in ST;
• The explanation part of the program and statements is stored between asterisks + brackets (**); the colon plus the equal sign indicates assignments in ST programming statements, etc.
• Commonly used decomposition sets are shown in the following table:

Delimiter	Application	Notes and examples
Space	Spaces can be inserted anywhere in the PLC program	Direct insertion of spaces in keywords, text, identifiers and enumeration values ​​is not allowed
TAB	TAB can be inserted anywhere in the PLC program	Direct insertion of TAB in keywords, text, identifiers and enumeration values ​​is not allowed
+	Decimal prefix symbol (positive number); Add operator	+456, +147; 22+78
-	Prefix sign of decimal number (negative number); Year-month-day separator; Subtraction operator	-753; D#2024-05-13; 15-2
#	Base number delimiter; Data type delimiter; Time literal delimiter	2#1110; SINT15; T#20ms
.	Separator for positive numbers and decimals; Hierarchical addressing address character; Structure element separator; Function block instance structure separator; Global namespace ;Namespace delimiter	3.14; IABC.3//IBC is a bit string data type; Channel[0].type/abc.number; TON1.Q; SYS .SR
E/e	Exponent delimiter	1.0e+6
' '	String start/end character	'HelloWorld'
$	The beginning of special characters in the string	'$L' means line feed; '$R' means carriage return
:	Time text delimiter; Variable/type delimiter	TOD#12:41:21.11; Test: INT
:=	Input variable connection operator; Assignment operator	INT_1(SINGLE:=Z2,PRIORITY:=1)
()	Subrange section break; Initialization repetition factor; Instruction list modifier; Function argument; Subexpression classification; Function block Input table delimiter	DATA:INT(-100..100); ARRAY[1..2,1..3] OF INT:=1,2,3(4),6; (A>B); ARlimit(Var1); (a(b-c)+d);< br/>TON_1(IN:=a,PT:=T#5m)
[]	Array subscript delimiter	ARRAY[1..2,1..3] OF INT; MMOD_5_CFG.CH[5].Range:=BI_10V
,	Array subscript delimiter; Function block initial value delimiter; Function block input table delimiter; Function argument table delimiter; Case to table delimiter Symbol	ARRAY[1..2,1..3] OF INT := 1,2,3(4),6; TON_1(IN:A,pt:=50ms) SR_1(S1:=A,REAL:=B); LIMIT(MN:=4,IN=A,MX:=20) CASETEP OF 1,5:DISPLAY:=FALSE
;	Statement separator	a:=15
..	Array range delimiter; Subrange; Case range delimiter	ARRAR[1..2]; DATA:INT(-1000..1000); CASETEPOF(1..5):display:=FALSE
%	Directly represents the prefix of the variable	%IW0
=>	Output connection operator	C10(CU:=iNPUT, Q=>Out)