Original
Character strings
A
character string, also called a string literal or string constant,
consists of a quoted string, a control string, or a combination
of quoted and control strings. Separators can occur only within quoted strings.
A quoted string
is a sequence of up to 255 characters from the extended ASCII character set,
written on one line and enclosed by apostrophes. A quoted string with nothing
between the apostrophes is a null string. Two sequential apostrophes in
a quoted string denote a single character, namely an apostrophe. For example,
'BORLAND' {
BORLAND }
'You''ll
see' { You'll see }
'''' {
' }
'' {
null string }
' ' {
a space }
A control
string is a sequence of one or more control characters, each of which
consists of the # symbol followed by an unsigned integer constant from 0 to 255
(decimal or hexadecimal) and denotes the corresponding ASCII character. The
control string
#89#111#117
is equivalent to the quoted string
'You'
You can
combine quoted strings with control strings to form larger character strings.
For example, you could use
'Line
1'#13#10'Line 2'
to put a carriage-return-line-feed between
Line 1 and Line 2. However, you cannot concatenate two quoted strings in this
way, since a pair of sequential apostrophes is interpreted as a single
character. (To concatenate quoted strings, use the + operator or simply combine them into a
single quoted string.)
A character string’s length is the number of characters in the string. A character string of any length is compatible with any string type and with the PChar type. A character string of length 1 is compatible with any character type, and, when extended syntax is enabled ({$X+}), a nonempty character string of length n is compatible with zero-based arrays and packed arrays of n characters. For more information about string types, see String types.
See also
Fundamental syntactic elements:
Overview
译文
字符串
字符串也叫做文本串或串常量，它由引用串、控制串组或二者联合组成。分隔符只能出现在引用串中。
在扩展ASCII字符集中，用前后两个单引号括起来的单个引用串是一个最长可达255个字符的序列。单引号之间没有字符的引用串是空串（null string）。引用串中连续的两个单引号表示一个字符，即单引号。例如：
'BORLAND' {
BORLAND }
'You''ll
see' { You'll see }
'''' {
' }
'' {
空串 }
' ' {
空格 }
控制串是有一个或更多控制字符的序列，每个控制字符都由 # 号及紧随其后的无符号整型常量（0..255之间，10进制或16进制）组成并且表示响应的ASCII字符。控制串
#89#111#117
等价于引用串
'You'
开可以联合引用串与控制串以构成大的字符串。例如，字符串
'Line
1'#13#10'Line 2'
在Line 1和Line2之间放置了回车换行。然而，不能通过这种方法连接两个引用串（例如不能试图将引用串 ‘Hello’ 与引用串 ‘World’连接在一起写成 ‘Hello’’World’，该字符串表示的是“Hello’World”，而不是预期结果），因为连续的两个引号将被解释成单个字符。（要连接两个引用串，可以使用串运算符中的加号 + 运算符或简单地将其合并到一对引号中，如’Hello’ + ‘World’，或者直接写成’HelloWorld’。）
字符串的长度是指串中字符的数量。任意长度的字符串与任意串类型（包括PChar类型）兼容。长度为1的字符串与任意字符类型兼容。此外，当扩充语法有效（编译指示{$X+}）时，长度为n的非空字符串与零基字符数组、容量为n的压缩字符数组兼容。有关串类型的更多信息，见串类型。
相关主题
编者注
零基数组形如 array
[0..m] of ...；零基字符数组形如 array
[0..m] of Char 。其中的m是非负的整数。压缩数组形如
packed
array [a..b] of ... 。下面的代码就字符数组与字符串兼容性进行了典型说明：
var
PA: packed array [2..5] of
Char; //压缩字符数组
A: array [0..5] of Char; //零基字符数组
B: array [2..5] of Char; //一般字符数组
S: string; //最常用的串
procedure
Test;
begin
PA := 'OK ?'; //类型兼容
A
:= 'Hello!'; //类型兼容
B
:= 'Bye.'; //类型兼容
ShowMessage(PA);
ShowMessage(A);
ShowMessage(B);
S := PA; //类型兼容
ShowMessage(S);
S := A; //类型兼容
ShowMessage(S);
S := B; //类型兼容
ShowMessage(S);
// PA := S; //类型不兼容
// A
:= S; //类型不兼容
// B
:= S; //类型不兼容
end;
通过本例还可以看出，字符串常量和字符串变量对字符数组的兼容性是有区别的（作为传递给过程ShowMessage的参数，定义的四个标识符兼容，而PA、A、B却都不能向S赋值）。