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Common Data Types in Free Pascal

Here is a list of common data types in Free Pascal, along with a simple example.

See the official docs for more info; Types.

Summary Table

Type Data Type Range / Size
Integer Byte 0 .. 255
Integer ShortInt -128 .. 127
Integer SmallInt -32,768 .. 32,767
Integer Integer -2,147,483,648 .. 2,147,483,647
Integer LongInt Same as Integer
Integer Int64 -9,223,372,036,854,775,808 .. 9,223,372,036,854,775,807
Integer Word 0 .. 65,535
Integer Cardinal 0 .. 4,294,967,295
Integer QWord 0 .. 18,446,744,073,709,551,615
Boolean Boolean True or False
Character Char ASCII characters
String String Default length 255 characters
Floating-Point Single ±1.5 x 10^−45 .. ±3.4 x 10^38
Floating-Point Real Similar to Single
Floating-Point Double ±5.0 x 10^−324 .. ±1.7 x 10^308
Floating-Point Extended More precise than Double (varies by implementation)
Enumerated Enum User-defined values
Subrange Subrange Defined range
Record Record User-defined complex type
Advanced Record Adv Record Records with methods
Array Static Array Fixed size
Array Dynamic Array Variable size
Pointer Pointer Memory address of a type

Integer Types

Byte

  • Range: 0 .. 255
  • Example:
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var
  b: Byte; 
begin   
  b := 100;   
  WriteLn(b); 
end.

ShortInt

  • Range: -128 .. 127
  • Example:
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var   
  s: ShortInt; 
begin   
  s := -50;   
  WriteLn(s); 
end.

SmallInt

  • Range: -32,768 .. 32,767
  • Example:
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var
  sm: SmallInt;
begin
  sm := 32000;
  WriteLn(sm);
end.

Integer

  • Range: -2,147,483,648 .. 2,147,483,647
  • Example:
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var
  i: Integer;
begin
  i := 1234567890;
  WriteLn(i);
end.

LongInt

  • Range: Same as Integer
  • Example:
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var
  li: LongInt;
begin
  li := -2147483648;
  WriteLn(li);
end.

Int64

  • Range: -9,223,372,036,854,775,808 .. 9,223,372,036,854,775,807
  • Example:
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var
  i64: Int64;
begin
  i64 := 9223372036854775807;
  WriteLn(i64);
end.

Word

  • Range: 0 .. 65,535
  • Example:
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var
  w: Word;
begin
  w := 65535;
  WriteLn(w);
end.

Cardinal

  • Range: 0 .. 4,294,967,295
  • Example:
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var
  c: Cardinal;
begin
  c := 4294967295;
  WriteLn(c);
end.

QWord

  • Range: 0 .. 18,446,744,073,709,551,615
  • Example:
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var
  qw: QWord;
begin
  qw := 18446744073709551615;
  WriteLn(qw);
end.

Boolean

  • Values: True or False
  • Example:
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var
  qw: QWord;
begin
  qw := 18446744073709551615;
  WriteLn(qw);
end.

Char (Character)

  • Range: 'A' .. 'Z', 'a' .. 'z', and other ASCII characters
  • Example:
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var
  c: Char;
begin
  c := 'A';
  WriteLn(c);
end.

String

  • Length: Default length is 255 characters
  • Example:
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var
  str: String;
begin
  str := 'Hello, Pascal!';
  WriteLn(str);
end.

Floating-Point Types

Single

  • Range: Approximately ±1.5 x 10^−45 .. ±3.4 x 10^38
  • Example:
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var
  s: Single;
begin
  s := 3.14;
  WriteLn(s);
end.

Real

  • Range: Varies by implementation, usually similar to Single
  • Example:
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var
  r: Real;
begin
  r := 2.71828;
  WriteLn(r);
end.

Double

  • Range: Approximately ±5.0 x 10^−324 .. ±1.7 x 10^308
  • Example:
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var
  d: Double;
begin
  d := 1.7976931348623157E+308;
  WriteLn(d);
end.

Extended

  • Range: Varies by implementation, generally more precise than Double
  • Example:
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var
  e: Extended;
begin
  e := 1.0e+308;
  WriteLn(e);
end.

Enumerated Types

  • Example:
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type
  TColor = (Red, Green, Blue);
var
  color: TColor;
begin
  color := Green;
  WriteLn(color);
end.

Subrange Types

  • Example:
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type
  TSmallRange = 1..100;
var
  r: TSmallRange;
begin
  r := 50;
  WriteLn(r);
end.

Record Types

  • Example:
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type
  TPerson = record
    Name: String;
    Age: Integer;
  end;
var
  person: TPerson;
begin
  person.Name := 'Alice';
  person.Age := 30;
  WriteLn(person.Name, ' is ', person.Age, ' years old.');
end.

Advanced Records (with methods)

  • Example:
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type
  TAdvancedPerson = record
    Name: String;
    Age: Integer;
    procedure DisplayInfo;
  end;
procedure TAdvancedPerson.DisplayInfo;
begin
  WriteLn(Name, ' is ', Age, ' years old.');
end;
var
  person: TAdvancedPerson;
begin
  person.Name := 'Bob';
  person.Age := 40;
  person.DisplayInfo;
end.

Arrays

Static Array

  • Example:
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var   
  arr: array[1..5] of Integer; 
begin   
  arr[1] := 10;
  WriteLn(arr[1]);
end.

Dynamic Array

  • Example:
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var
  arr: array of Integer;
  i: Integer;
begin
  SetLength(arr, 5);

  for i := 0 to High(arr) do
    arr[i] := i * 10;

  for i := 0 to High(arr) do
    WriteLn(arr[i]);
end.

Pointers

  • Example:
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var
  p: ^Integer;
  x: Integer; 
begin   
  New(p);
  p^ := 10;
  x := p^;
  WriteLn(x);
  Dispose(p); 
end.