Programming in Free Pascal language

The most important commands from Free Pascal programming language in one place, a unique comparison and each command-operator is shown using a piece of program. Statements-operators of these sample programs are clickable, so with a simple click we have more information available.

Programming language Free Pascal:

Lexical elements

Types and variables

Program structure

Operators

Statements

Lexical elements

Lexical elements are numeric, string constants and comments in the code.

Types and variables

Types and variables are closely related because variables are the most important elements of our program in which we store data, partial results of our calculations. Types tell us what data can be stored in variables.

Basic data types - Simple data types that can be numbers, characters, or logical types. They are suitable for storing one value.
- Logical Boolean data type: boolean
- Numbers - Types for storing numbers.
  - Integers - Types for storing integers.
    - Unsigned - Types for storing unsigned integers.
      8-bit unsigned integer: byte 16-bit unsigned integer: word 32-bit unsigned integer: longword 64-bit unsigned integer: UInt64, qword
    - Signed - Types for storing signed integers.
      8-bit integer: shortint 16-bit integer: smallint 32-bit integer: longint 64-bit integer: Int64
  - Real numbers 32-bit real number: single 64-bit real number: double
Type conversions - Using a type conversion we can change the type of existing types. Thanks to this we can overwrite automatic conversion.
- Explicit - By using an explicit conversion, you can specify exactly what type you want to work with. Thanks to this we can overwrite automatic conversion.
  To 8-bit integer: shortint To 8-bit unsigned integer: byte To 16-bit integer: smallint To 16-bit unsigned integer: word To 32-bit integer: longint To 32-bit unsigned integer: longword To 64-bit integer: Int64 To 64-bit unsigned integer: QWord To 32-bit real number: single To 64-bit real number: double To boolean: Boolean
Variables - Variable is used for storing the data. can be declared in different locations and can be used in different locations. it can be distinguished according to the lifetime: they are global or local static variables. it is possible use in the structure or function.
Variable declaration Variable use

Program structure

Operators

Operators perform an operation between the operands, this operation can be mathematical, logical, or bitwise.

Parenthesis operator: ( )

Arithmetic operators - Are used to perform mathematical operations. the following are basic operations between the arithmetic operators:
Addition: + Subtraction: - Multiplication: * Division: / Integer division: div Modulo: mod Additive inverse: -
Logical - Three or four logical operations are available, exactly how much it depends on the particular programming language that we use. with these operations, we can solve any logical task or condition. these logical conditions are for example connections of comparing values according to certain rules, testing values. logical operations are mainly used in the execution of conditional statements.
Logical and: and Logical or: or Logical negation: not
Bitwise - We have more of the bitwise operators, using the bitwise operator we can set or determine the specific bit in whole numbers.
Bitwise left shift: shl Bitwise right shift: shr Bitwise and: and Bitwise or: or Bitwise not: not Bitwise xor: xor
Relational - The main use of the relational operators is in control of conditional statements. thanks to these, we can decide which direction to continue the conditional statements, or for example, how many iterations of the cycle need to perform.
Less than: < Greater than: > Less than or equal to: <= Greater than or equal to: >= Equal to: = Not equal to: <>
Assignment Assignment: :=

Statements

Statements are important elements for writing programs. Generally one statement line corresponds to one line program. The main group of the statements are: cycles, program branching and flow control.

Block statement: begin end

Free Pascal

 i := x * 5;
 while i>0 do
   if i=10 then
     break
   else 
   begin
     dec(i)
   end;

Examples - Free Pascal

Free Pascal

a and b
a and true
10 >a and a>5

Free Pascal

xmin := 0; ymax := 255;
x:=5;           // x = 5
y:= 15 mod 4;    // y = 3
y := byte((x * y));  // z = 15

Free Pascal

Other pieces of example codes:

if  y < 100 then  
   inc(x);

2 shl 2

b3:= Boolean( 0);

y + 3

15 +7.5

x = 6

Programming languages

Compiler