Byte: what changed
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Title: Byte
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| 1 | + | A `byte` is an unsigned [[Integer|integer]] in the range of `0..255`. A `byte` is 8 bits long. A `byte` and a [[Char|char]] are virtually the same thing as of version 3 of [[FPC]]. | |
| 2 | + | ||
| 3 | + | ## Valid values | |
| 4 | + | ||
| 5 | + | The key difference is, a `byte` can only be referred to as a numeric [[Type|type]], while a `char` can be used as a character, or as part of a string type, and cannot be used in an arithmetic expression. A `byte` will always be the same size as an [[AnsiChar|ansiChar]], but in the future `char` may be considered a synonym for [[WideChar|wideChar]], not `ansiChar`. | |
| 6 | + | ||
| 7 | + | For example: | |
| 8 | + | ||
| 9 | + | ``` pascal | |
| 10 | + | program byteDemo(input, output, stderr); | |
| 11 | + | ||
| 12 | + | var | |
| 13 | + | foo: byte; | |
| 14 | + | bar: char; | |
| 15 | + | ||
| 16 | + | begin | |
| 17 | + | // those two assignments are physically the same | |
| 18 | + | foo := 65; | |
| 19 | + | bar := 'A'; | |
| 20 | + | ||
| 21 | + | // although they are the same action, | |
| 22 | + | // the following would be illegal | |
| 23 | + | //foo := 'A'; | |
| 24 | + | //bar := 65; | |
| 25 | + | end. | |
| 26 | + | ``` | |
| 27 | + | ||
| 28 | + | The use of `byte` or `byte` as a data type provides better documentation as to the purpose of the use of the particular variable. | |
| 29 | + | ||
| 30 | + | ## Standard functions | |
| 31 | + | ||
| 32 | + | ### Conversion to and from character | |
| 33 | + | ||
| 34 | + | The `byte` type can be [[coersion|coerced]] to `char` by using the [[Chr|chr function]]. Char type values can be coerced to byte by using the [[Ord|ord function]]. | |
| 35 | + | ||
| 36 | + | The above program corrected to legal use: | |
| 37 | + | ||
| 38 | + | ``` pascal | |
| 39 | + | program ordChrDemo(input, output, stderr); | |
| 40 | + | ||
| 41 | + | var | |
| 42 | + | foo: byte; | |
| 43 | + | bar: char; | |
| 44 | + | ||
| 45 | + | begin | |
| 46 | + | foo := 65; | |
| 47 | + | bar := 'A'; | |
| 48 | + | ||
| 49 | + | foo := ord('A'); | |
| 50 | + | // chr(65) is equivalent to #65 | |
| 51 | + | bar := chr(65); | |
| 52 | + | bar := #65; | |
| 53 | + | ||
| 54 | + | // alternatively: typecasts | |
| 55 | + | // typecasts of constant expressions | |
| 56 | + | // are guaranteed to happen at compile-time | |
| 57 | + | foo := byte('A'); | |
| 58 | + | bar := char(65); | |
| 59 | + | end. | |
| 60 | + | ``` | |
| 61 | + | ||
| 62 | + | ### String representation | |
| 63 | + | ||
| 64 | + | The [`binStr` function](https://www.freepascal.org/docs-html/rtl/system/binstr.html) from the [[System unit|system unit]] can be used to get a [[String|string]] showing the [[Binary numeral system|binary representation]] of a `byte`: | |
| 65 | + | ||
| 66 | + | ``` pascal | |
| 67 | + | program binStrDemo(input, output, stderr); | |
| 68 | + | ||
| 69 | + | var | |
| 70 | + | foo: byte; | |
| 71 | + | ||
| 72 | + | begin | |
| 73 | + | foo := 10; | |
| 74 | + | writeLn(binStr(foo, 8)); | |
| 75 | + | end. | |
| 76 | + | ``` | |
| 77 | + | ||
| 78 | + | The output is: | |
| 79 | + | ||
| 80 | + | ```text | |
| 81 | + | 00001010 | |
| 82 | + | ``` | |
| 83 | + | ||
| 84 | + | A more versatile function is [`intToBin` provided by the `strUtils` unit](https://www.freepascal.org/docs-html/rtl/strutils/inttobin.html). | |
| 85 | + | ||
| 86 | + | --- | |
| 87 | + | *From the Free Pascal wiki, page "Byte", as it stood on 2022-05-26 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).* |