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Global Parameters 9!:

9!:(2*n) queries a parameter and (if available) 9!:(1+2*n) sets it. In versions of J with a GUI, these parameters are usually queried and set by the menu item   Edit|Configure...

9!:0 y
9!:1 y
Random Seed. See Roll/Deal (?).
9!:2 y
9!:3 y
Default Displays. The representation(s) to used for default displays of non-nouns. The representations are as defined in 5!:n : 1 atomic, 2 boxed, 4 tree, 5 linear, 6 paren.
9!:6 y
9!:7 y
Box-Drawing Characters. The eleven characters used to draw boxes (initially +++++++++|-).

9!:8 y
9!:9 y
Error Messages. e.g. replace English messages (default) by French.
9!:10 y
9!:11 y
Print Precision. The print precision in default output (initially 6). The precision in particular cases can be set using fit, thus: ":!.p
9!:12 y System Type.
 5 Unix
 6Windows32 (95/98/2000/NT)
 7Windows CE
9!:14 y J Version. For example:
   9!:14 ''
9!:16 y
9!:17 y
Boxed Display Positioning. y is r,c specifying row and column positioning: 0 (top, left); 1 (centre); 2 (bottom, right)
9!:18 y
9!:19 y
Comparison Tolerance. Queries and sets the comparison tolerance. See Equal (=). The tolerance in particular cases can be set using fit, thus: =!.t .
9!:20 y
9!:21 y
Memory Limit. An upper bound on the size of any one memory allocation. The memory limit is initially 2^30 on 32-bit systems and 2^62 on 64-bit systems.
9!:24 y
9!:25 y
Security Level. The security level is either 0 or 1. It is initially 0, and may be set to 1 (and can not be reset to 0). When the security level is 1, executing Window driver commands and certain foreigns (!:) that can alter the external state cause a “security violation” error to be signalled. The following foreigns are prohibited: dyads 0!:n , 1!:n except 1!:40 , 1!:41, and 1!:42 , 2!:n , and 16!:n .
9!:26 y
9!:27 y
Immex Phrase. See 9!:28 and 9!:29 .
9!:28 y
9!:29 y
Immex Flag. If the immediate execution flag is 1, then on entry into immediate execution, the flag is set to 0 and the immediate execution phrase (9!:27) is executed.
9!:32 y
9!:33 y
Execution Time Limit. The execution time limit is a single non-negative (possibly non-integral) number of seconds. The limit is reduced for every line of immediate execution that exceeds a minimum granularity, and execution is interrupted with a “time limit error” if a non-zero limit is set and goes to 0. Current limitations:
  • The resolution is milliseconds.
  • Under Windows the limit is on elapsed time while J is running, instead of the task processor time as is intended.
  • Under Windows the granularity is approximately 1.5 seconds.
   9!:32 ''                    query execution time limit; none is set
   9!:33 ]5.25                 set limit to 5.25 seconds
   9!:32 ''                    current setting

   # %. ? 100 100 $ 1e6        below granularity
   9!:32 ''                    limit unchanged

   ".10#,:'# %. ?(2#100)$1e6'  above granularity
100 100 100 100 100 100 100 100 100 100
   9!:32 ''                    limit reduced

   ".10#,:'# %. ?(2#100)$1e6'  limit exceeded
|time limit
|   #    %.?100 100$1000000
   9!:32 ''
9!:34 y
9!:35 y
Assertions. 1 if and only if assertions are to be evaluated, with a default setting of 1. See the assert. control word.
9!:36 y
9!:37 y
Output Control. A 4-element vector that controls session manager output:
end-of-line sequence    0 line feed; 2 carriage return line feed
maximum line length Output lines are truncated at this length and “...” appended.
maximum line before    If the total number of output lines exceeds the sum of “maximum lines before” b and “maximum lines after” a , then the first b lines are output, followed by a line of “...”, followed by the last a lines.
maximum line after See above.

The defaults for output controls are 0 256 0 222 .
9!:38 y
9!:39 y
Locale Hash Table Size. A 2-element vector that controls the default hash table sizes for named and numbered locales, with a default of 3 2 . A specified size of i indicates a table requiring w*2^6+i bytes where w is the number of bytes in a word. A larger hash table size improves performance; regardless of the hash table size, a locale may contain an effectively unlimited number of names.

The following table lists the initial hash table sizes:
 Category Index   # Entries
named locales   3  499
numbered locales   2  241
table of all named locales    3  499
explicit definition locals   1  113
base   5  2029
z   7  8179

The hash table size of a locale can be individually specified when the locale is created, using the dyad 18!:3 .
9!:40 y
9!:41 y
Retain Comments and White Space. Specifies whether comments and non-essential white space are retained in explicit definitions. The default is 1 (retain comments and white space). A setting of 1 can result in explicit definitions, even commentless ones, requiring double the amount of storage.
9!:42 y
9!:43 y
RNG Select. See Roll/Deal (?).
9!:44 y
9!:45 y
RNG State. See Roll/Deal (?).
9!:46 y
9!:47 y
“Break” File. The name of the file used for “break” handling.
9!:48 y
9!:49 y
Explicit Argument Names. This is a temporary facility that controls whether the names x. y. u. v. m. n. are permitted.

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