Signed variable - Revision history

Actual-nh: Grammar/style

2021-05-23T15:36:33Z

Grammar/style

Jayt: category:development

2006-09-20T15:40:14Z

category:development

Eidolos: Another spelling error.. bad Eidolos!

2006-08-26T17:27:27Z

Another spelling error.. bad Eidolos!

Eidolos: Signedness isn't spelled signedeness, oops :) Also a cleverly hidden link to integer overflow.

2006-08-26T17:18:14Z

Signedness isn't spelled signedeness, oops :) Also a cleverly hidden link to integer overflow.

Ray Chason: Notes on pre-ISO coding practices; non-two's complement notations

2006-08-26T17:09:10Z

Notes on pre-ISO coding practices; non-two's complement notations

Eidolos: Rewrote first sentence.

2006-08-26T16:50:19Z

Rewrote first sentence.

Eidolos: Expanded.

2006-08-26T16:38:11Z

Expanded.

Jayt: moved info from scumming

2006-08-26T11:30:37Z

moved info from scumming

New page

A '''signed variable''' is a data type used within the NetHack [[source code]]. Its use is reponsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest [[AC]] attainable is -128, because the AC value is stored in a signed char variable (<code>schar</code>) which can (on most platforms) store up to 256 values: 127 positive numbers, zero, and 128 negative numbers.

{{stub|Would a C-head like to clarify "on most platforms", and expand this article to explain other data types?}}

[[Category:Annotations]]

@@ Line 1: / Line 1: @@
 {{Wikipedia|Signed number representations}}
-'''Signedness''' is a property of nearly all of the numeric data types used within the NetHack [[source code]]. The word "signed" refers to the fact that these variables can store negative values; unsigned variables cannot. Its use is reponsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest [[AC]] attainable on most machines is -128, because the AC value is stored in a signed 8-bit variable (<code>schar</code>) which can store up to 256 values: 127 positive numbers, zero, and 128 negative numbers. The lack of symmetry is due to the use of [[wikipedia:Two's complement|two's complement]]. An unsigned 8-bit variable would be able to store zero and 255 positive values.
+'''Signedness''' is a property of nearly all of the numeric data types used within the NetHack [[source code]]. The word "signed" refers to that these variables can store negative values; unsigned variables cannot. Their use is responsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest [[AC]] attainable on most machines is -128, because the AC value is stored in a signed 8-bit variable (<code>schar</code>) which can store up to 256 values: 127 positive numbers, zero, and 128 negative numbers. The lack of symmetry is due to the use of a [[wikipedia:Two's complement|two's complement]] representation. An unsigned 8-bit variable would be able to store zero and 255 positive values.
 Some older machines use other [[wikipedia:Signed number representations|signed number representations]], ending up with a different range of integers than two's complement.  These notations are rarely seen on the average person's desktop.  (Excess-N notation is still used for exponents of floating point numbers, but is rare for integers.)
-Signed variables are ubiquitious in the NetHack source code, even where it doesn't particularly make sense.  This is possibly due to different coding practices that prevailed among early developers -- [[Hack 1.0]] was released in December 1984, well before [[ISO C]] existed, and developers wrote their C code in quite different styles than what prevails today. Unsigned variables were possibly a new addition to C, and then-active programmers were not yet accustomed to using them.
+Signed variables are ubiquitous in the NetHack source code, even where it doesn't particularly make sense.  This is possibly due to different coding practices that prevailed among early developers -- [[Hack 1.0]] was released in December 1984, well before [[ISO C]] existed, and developers wrote their C code in quite different styles than what prevails today. Unsigned variables were possibly a new addition to C, and then-active programmers were not yet accustomed to using them.
 [[Score]], for example, is a signed variable (whose magnitude is dependent on machine word size; generally it's 32 bits, but today computers are shifting to 64-bit). Does a negative score make sense? It'd almost certainly be better to have the additional 2147483648 positive score values. Portability might be an issue -- perhaps unsigned variables are less portable than signed ones. Or it could be that the [[DevTeam]] simply didn't think anyone would achieve two billion points.

← Older revision		Revision as of 15:40, 20 September 2006
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	Whether a variable is signed or not affects what happens during [[integer overflow]].		Whether a variable is signed or not affects what happens during [[integer overflow]].

−	[[Category:~~Annotations~~]]	+	[[Category:Development]]

@@ Line 5: / Line 5: @@
 Some older machines use other [[wikipedia:Signed number representations|signed number representations]], ending up with a different range of integers than two's complement.  These notations are rarely seen on the average person's desktop.  (Excess-N notation is still used for exponents of floating point numbers, but is rare for integers.)
-Signed variables are ubiquitious in the NetHack source code, even where it doesn't particularly make sense.  This is possibly due to different coding practices that prevailed among early developers -- [[Hack 1.0]] was released in December 1984, well before [[ISO C]] existed, and developers wrote their C code in quite different styles than what prevails today.  Unsigned variables were possibly a new addition to C, and then-active programmers were not yet accustomed to using them.
+Signed variables are ubiquitious in the NetHack source code, even where it doesn't particularly make sense.  This is possibly due to different coding practices that prevailed among early developers -- [[Hack 1.0]] was released in December 1984, well before [[ISO C]] existed, and developers wrote their C code in quite different styles than what prevails today. Unsigned variables were possibly a new addition to C, and then-active programmers were not yet accustomed to using them.
-[[Score]], for example, is a signed variable (whose magnititude is dependent on machine word size; generally it's 32 bits, but today computers are shifting to 64-bit). Does a negative score make sense? It'd almost certainly be better to have the additional 2147483648 positive score values. Portability might be an issue -- perhaps unsigned variables are less portable than signed ones. Or it could be that the [[DevTeam]] simply didn't think anyone would achieve two billion points.
+[[Score]], for example, is a signed variable (whose magnitude is dependent on machine word size; generally it's 32 bits, but today computers are shifting to 64-bit). Does a negative score make sense? It'd almost certainly be better to have the additional 2147483648 positive score values. Portability might be an issue -- perhaps unsigned variables are less portable than signed ones. Or it could be that the [[DevTeam]] simply didn't think anyone would achieve two billion points.
 Whether a variable is signed or not affects what happens during [[integer overflow]].
 [[Category:Annotations]]

@@ Line 1: / Line 1: @@
 {{Wikipedia|Signed number representations}}
-'''Signedeness''' is a property of nearly all of the numeric data types used within the NetHack [[source code]]. The word "signed" refers to the fact that these variables can store negative values; unsigned variables cannot. Its use is reponsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest [[AC]] attainable on most machines is -128, because the AC value is stored in a signed 8-bit variable (<code>schar</code>) which can store up to 256 values: 127 positive numbers, zero, and 128 negative numbers. The lack of symmetry is due to the use of [[wikipedia:Two's complement|two's complement]]. An unsigned 8-bit variable would be able to store zero and 255 positive values.
+'''Signedness''' is a property of nearly all of the numeric data types used within the NetHack [[source code]]. The word "signed" refers to the fact that these variables can store negative values; unsigned variables cannot. Its use is reponsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest [[AC]] attainable on most machines is -128, because the AC value is stored in a signed 8-bit variable (<code>schar</code>) which can store up to 256 values: 127 positive numbers, zero, and 128 negative numbers. The lack of symmetry is due to the use of [[wikipedia:Two's complement|two's complement]]. An unsigned 8-bit variable would be able to store zero and 255 positive values.
 Some older machines use other [[wikipedia:Signed number representations|signed number representations]], ending up with a different range of integers than two's complement.  These notations are rarely seen on the average person's desktop.  (Excess-N notation is still used for exponents of floating point numbers, but is rare for integers.)
@@ Line 8: / Line 8: @@
 [[Score]], for example, is a signed variable (whose magnititude is dependent on machine word size; generally it's 32 bits, but today computers are shifting to 64-bit). Does a negative score make sense? It'd almost certainly be better to have the additional 2147483648 positive score values. Portability might be an issue -- perhaps unsigned variables are less portable than signed ones. Or it could be that the [[DevTeam]] simply didn't think anyone would achieve two billion points.
 [[Category:Annotations]]

@@ Line 1: / Line 1: @@
-'''Signedeness''' is a property of nearly all of the numeric data types used within the NetHack [[source code]]. The word "signed" refers to the fact that these variables can store negative values; unsigned variables cannot. Its use is reponsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest [[AC]] attainable is -128, because the AC value is stored in a signed 8-bit variable (<code>schar</code>) which can store up to 256 values: 127 positive numbers, zero, and 128 negative numbers. The lack of symmetry is due to the use of [http://en.wikipedia.org/wiki/Two%27s_complement two's complement]. An unsigned 8-bit variable would be able to store zero and 255 positive values.
+{{Wikipedia|Signed number representations}}
-Signed variables are ubiquitious in the NetHack source code, even where it doesn't particularly make sense. [[Score]], for example, is a signed variable (whose magnititude is dependent on machine word size; generally it's 32 bits, but today computers are shifting to 64-bit). Does a negative score make sense? It'd almost certainly be better to have the additional 2147483648 positive score values. Portability might be an issue -- perhaps unsigned variables are less portable than signed ones. Or it could be that the [[DevTeam]] simply didn't think anyone would achieve two billion points.
+'''Signedeness''' is a property of nearly all of the numeric data types used within the NetHack [[source code]]. The word "signed" refers to the fact that these variables can store negative values; unsigned variables cannot. Its use is reponsible for the many seemingly non-round numbers found as limits within the game. For example, the lowest [[AC]] attainable on most machines is -128, because the AC value is stored in a signed 8-bit variable (<code>schar</code>) which can store up to 256 values: 127 positive numbers, zero, and 128 negative numbers. The lack of symmetry is due to the use of [[wikipedia:Two's complement|two's complement]]. An unsigned 8-bit variable would be able to store zero and 255 positive values.
 [[Category:Annotations]]