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   Defines a symbolic name for a character string or integer value.

   Format

     symbol-name =[=] expression

     symbol-name[bit-position,size] =[=] replacement-expression

                                  NOTE

      Digital advises against assigning a symbolic name that is
      already a DCL command name. Digital especially discourages
      the assignment of symbols such as IF, THEN, ELSE, and GOTO,
      which can affect the interpretation of command procedures.
 

2  Parameters
 

symbol-name

   Specifies a string of 1 to 255 characters for the symbol name.
   The name can contain any alphanumeric characters from the DEC
   Multinational character set, the underscore (_),  and the dollar
   sign ($).  However, the name must begin only with an alphabetic
   character (uppercase and lowercase characters are equivalent),
   an underscore, or a dollar sign. Using one equal sign (=)  places
   the symbol name in the local symbol table for the current command
   level. Using two equal signs (==) places the symbol name in the
   global symbol table.
 

expression

   Names the value on the right-hand side of an assignment
   statement. This parameter can consist of a character string, an
   integer, a symbol name, a lexical function, or a combination of
   these entities. The components of the expression are evaluated,
   and the result is assigned to the symbol. All literal character
   strings must be enclosed in quotation marks (" ").  If the
   expression contains a symbol, the expression is evaluated using
   the symbol's value.

   The result of expression evaluation is either a character string
   or a signed integer value. If the expression is evaluated as a
   string, the symbol is assigned a string value. If the expression
   is evaluated as an integer, the symbol is assigned an integer
   value. If the integer value exceeds the capacity of the 4-byte
   buffer that holds it, no error message is issued.

   For a summary of operators used in expressions, details on
   how to specify expressions, and details on how expressions are
   evaluated, see the OpenVMS User's Manual.

   DCL uses a buffer that is 1024 bytes long to hold an assignment
   statement and to evaluate the expression. The length of the
   symbol name, the expression, and the expression's calculations
   cannot exceed 1024 bytes.
 

[bit-position,size]

   States that a binary overlay is to be inserted in the current
   32-bit value of a symbol name. The current value of the symbol
   name is evaluated. Then, the specified number of bits is replaced
   by the result of the replacement expression. The bit position is
   the location relative to bit 0 at which the overlay is to occur.
   If the symbol you are overlaying is an integer, then the bit
   position must be less than 32. The sum of the bit position and
   the size must be less than or equal to 32.

   If the symbol you are overlaying is a string, then the bit
   position must be less than 6152. Because each character is
   represented using 8 bits, you can begin an overlay at any
   character through the 768th character. (The 768th character
   starts in bit position 6144.) The sum of the bit position and
   the size must be less than or equal to 6152.

   The size is the number of bits to be overlaid. If you specify a
   size that is greater than 32, DCL reduces the size to 32.

   The brackets are required notation; no spaces are allowed between
   the symbol name and the left bracket. Specify values for the bit
   position and size as integers.
 

replacement-expression

   Specifies the value that is used to overlay the symbol you are
   modifying. Specify the replacement expression as an integer.

   If the symbol you are modifying is an integer, the replacement
   expression defines a bit pattern that is overlaid on the value
   assigned to the symbol. If the symbol you are modifying is
   a character string, the result of the replacement expression
   defines a bit pattern that is overlaid on the specified bits
   of the character string. If the symbol you are modifying is
   undefined, the result of the replacement expression is overlaid
   on a null string.
 

2  Examples

   1.$ LIST == "DIRECTORY"

     The assignment statement in this example assigns the user-
     defined synonym LIST as a global symbol definition for the DCL
     command DIRECTORY.

   2.$ COUNT = 0
     $ LOOP:
     $      COUNT = COUNT + 1
     $      IF P'COUNT' .EQS. "" THEN EXIT
     $      APPEND/NEW &P'COUNT' SAVE.ALL
     $      DELETE &P'COUNT';*
     $      IF COUNT .LT. 8 THEN GOTO LOOP
     $ EXIT

     This command procedure, COPYDEL.COM, appends files (specified
     as parameters) to a file called SAVE.ALL. After a file has been
     appended, the command procedure deletes the file. Up to eight
     file names can be passed to the command procedure. The file
     names are assigned to the symbols P1, P2, and so on.

     The command procedure uses a counter to refer to parameters
     that are passed to it. Each time through the loop, the
     procedure uses an IF command to check whether the value of
     the current parameter is a null string. When the IF command is
     scanned, the current value of the symbol COUNT is concatenated
     with the letter P. The first time through the loop, the IF
     command tests P1; the second time through the loop it tests
     P2, and so on. After the expression P'COUNT' is evaluated, the
     substitution of the file names that correspond to P1, P2, and
     so on is automatic within the context of the IF command.

     The APPEND and DELETE commands do not perform any substitution
     automatically, because they expect and require file
     specifications as input parameters. The ampersand (&) precedes
     the P'COUNT' expression for these commands to force the
     appropriate symbol substitution. When these commands are
     initially scanned each time through the loop, COUNT is
     substituted with its current value. Then, when the commands
     execute, the ampersand causes another substitution: the first
     file specification is substituted for P1, the second file
     specification is substituted for P2, and so on.

     To invoke this procedure, use the following command:

       $ @COPYDEL ALAMO.TXT BEST.DOC

     The files ALAMO.TXT and BEST.DOC are each appended to the file
     SAVE.ALL and are then deleted.

   3.$ A = 25
     $ CODE = 4 + F$INTEGER("6") - A
     $ SHOW SYMBOL CODE
       CODE = -15   HEX = FFFFFFF1   Octal = 1777761

     This example contains two assignment statements. The first
     assignment statement assigns the value 25 to the symbol A. The
     second assignment statement evaluates an expression containing
     an integer (4), a lexical function (F$INTEGER("6")), and the
     symbol A. The result of the expression, -15, is assigned to the
     symbol CODE.

   4.$ FILENAME = "JOBSEARCH" - "JOB"
     $ FILETYPE = ".OBJ"
     $ FILESPEC = FILENAME + FILETYPE
     $ TYPE 'FILESPEC'

     The first command in this example assigns the symbol FILENAME
     the value "SEARCH". Notice that the string "SEARCH" is the
     result of the string reduction operation performed by the
     expression. The second command assigns the symbol FILETYPE
     the character string ".OBJ". The symbols FILENAME and FILETYPE
     are then added together in an expression assigned to the
     symbol FILESPEC. Because the values of the symbols FILENAME
     and FILETYPE are concatenated, the resultant value assigned
     to FILESPEC is the character string "SEARCH.OBJ". The symbol
     FILESPEC is then used as a parameter for the TYPE command. The
     single quotation marks (' ')  request the command interpreter
     to replace the symbol FILESPEC with its value SEARCH.OBJ. Thus,
     the TYPE command types the file named SEARCH.OBJ.

   5.$ BELL[0,32] = %X07
     $ SHOW SYMBOL BELL
       BELL = ""

     In this example, the symbol BELL is created with an arithmetic
     overlay assignment statement. Because the symbol BELL is
     previously undefined, the hexadecimal value 7 is inserted
     over a null character string and is interpreted as the ASCII
     code for the bell character on a terminal. When you issue the
     command SHOW SYMBOL BELL, the terminal beeps.

     If the symbol BELL had been previously defined with an integer
     value, the result of displaying BELL would have been to show
     its new integer value.

   6.$ $=34
     %DCL-W-NOCOMD, no command on line - reenter with alphabetic first
     character
     $ $$=34
     $ SHOW SYMBOL $$
     %DCL-W-UNDSYM, undefined symbol - check validity and spelling
     $ SHOW SYMBOL $
     $ = 34   Hex = 00000022  Octal = 00000000042

     If you begin a symbol name with the dollar sign ($),  use two
     dollar signs ($$)  because DCL discards the first instance of
     the dollar sign.
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