char

A character char is 1 byte in pascal.

AnsiChar is an alias to Char. See https://www.freepascal.org/docs-html/rtl/system/ansichar.html.

'a' is a char. Note only single quote is used. Double quotes are not correct.

See https://wiki.freepascal.org/Character_and_string_types for different types of strings:

• AnsiChar

• Static array of char

• Dynamic array of char, see also https://www.freepascal.org/docs-html/rtl/system/setlength.html We need to free the memory by passing 0 to SetLength

var
  a: char;
begin
  a := 'a';
  a := #65; // equivalent to a := 'a'

  a := ''''; // a is a single quote here.
end.

There is also a string type, which can contain at most 255 characters.

var
  s: string;
  s2: string[255]; // both s ans s2 have 256 bytes.
 begin
   writeln ('SizeOf(s) is ', SizeOf(s)); // Sizeof(s) is 256
   writeln ('SizeOf(s2) is ', SizeOf(s2)); // Sizeof(s2) is 256
   s := 'hello';
   writeln('s[0] is ', ord(s[0])); // s[0] is 5
 end.

Note var s: string[size] will allocate size + 1 bytes. size can be any value from 1 to 255. s[0] contains the length of the string. If [size] is not specified, then it is equivalent to [255].

pchar:

• It is similar to the strings in C, which ends with 0. pchar is a pointer

• See https://www.freepascal.org/docs-html/ref/refsu12.html

var
 p: pchar;
begin
  p := 'hello world';
  writeln ('p is ', p); // p is hello world
end.

Example 2:

var
 s: string;
 p: pchar;
begin
  s := 'hello world'#0; // Use #0 to append a \0 at the end
  p := @s[1]; // s[0] is the length of the string, so we use @s[1] here
  writeln ('p is ', p); // p is hello world
end.

• Use StrLen for pchar, but use Length for string.