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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 (such as Windows), these parameters are usually queried and set by the menu item Edit|Configure...

`9!:0 y 9!:1 y` | Random Seed. Queries and sets the random seed used in pseudo-random number generation in the verb`` Roll/Deal (`?`).`` The initial value is`7^5` .
`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.

`0` | PC
`1` | PC386
`2` | Windows
`3` | Macintosh``
`4` | OS2

`5` | Unix
`6` | Windows32 (95/98/2000/NT)
`7` | Windows CE
`_1` | Other

`9!:14 y`

J Version. For example:

       9!:14 ''
    4.01/1998-03-15/10:24

`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`,`8!:n`,`14!:n`, `15!: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 immediate execution phrase`` (`9!:27`)`` is executed and the flag is set to 0.

`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.

Examples:

       9!:32 ''                    query execution time limit; none is set
    0
       9!:33 ]5.25                 set limit to 5.25 seconds
       9!:32 ''                    current setting
    5.25

       # %. ? 100 100 $ 1e6        below granularity
    100
       9!:32 ''                    limit unchanged
    5.25

       ".10#,:'# %. ?(2#100)$1e6'  above granularity
    100 100 100 100 100 100 100 100 100 100
       9!:32 ''                    limit reduced
    2.226

       ".10#,:'# %. ?(2#100)$1e6'  limit exceeded
    |time limit
    |   #    %.?100 100$1000000
       9!:32 ''
    0

`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.

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