mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-11-23 06:03:07 +03:00
207 lines
6.6 KiB
Markdown
207 lines
6.6 KiB
Markdown
---
|
||
language: Pascal
|
||
filename: learnpascal.pas
|
||
contributors:
|
||
- ["Ganesha Danu", "http://github.com/blinfoldking"]
|
||
- ["Keith Miyake", "https://github.com/kaymmm"]
|
||
---
|
||
|
||
|
||
>Pascal is an imperative and procedural programming language, which Niklaus Wirth designed in 1968–69 and published in 1970, as a small, efficient language intended to encourage good programming practices using structured programming and data structuring. It is named in honor of the French mathematician, philosopher and physicist Blaise Pascal.
|
||
source : [wikipedia](https://en.wikipedia.org/wiki/Pascal_(programming_language))
|
||
|
||
|
||
|
||
To compile and run a pascal program you could use a free pascal compiler. [Download Here](https://www.freepascal.org/)
|
||
|
||
```pascal
|
||
//Anatomy of a Pascal Program
|
||
//this is a comment
|
||
{
|
||
this is a
|
||
multiline comment
|
||
}
|
||
|
||
//name of the program
|
||
program learn_pascal; //<-- don't forget a semicolon
|
||
|
||
const
|
||
{
|
||
this is where you should declare constant values
|
||
}
|
||
type
|
||
{
|
||
this is where you should declare custom
|
||
data-types
|
||
}
|
||
var
|
||
{
|
||
this is where you should declare a variable
|
||
}
|
||
|
||
//main program area
|
||
begin
|
||
{
|
||
area to declare your instruction
|
||
}
|
||
end. // End of a main program area should require a "." symbol
|
||
```
|
||
|
||
```pascal
|
||
//When declaring variables
|
||
//you can do this
|
||
var a:integer;
|
||
var b:integer;
|
||
//or this
|
||
var
|
||
a : integer;
|
||
b : integer;
|
||
//or this
|
||
var a,b : integer;
|
||
```
|
||
|
||
```pascal
|
||
program Learn_More;
|
||
//Let's learn about data types and their operations
|
||
|
||
const
|
||
PI = 3.141592654;
|
||
GNU = 'GNU''s Not Unix';
|
||
// constants are conventionally named using CAPS
|
||
// their values are fixed and cannot be changed during runtime
|
||
// holds any standard data type (integer, real, boolean, char, string)
|
||
|
||
type
|
||
ch_array : array [0..255] of char;
|
||
// arrays are new 'types' specifying the length and data type
|
||
// this defines a new data type that contains 255 characters
|
||
// (this is functionally equivalent to a string[256] variable)
|
||
md_array : array of array of integer;
|
||
// nested arrays are equivalent to multidimensional arrays
|
||
// can define zero (0) length arrays that are dynamically sized
|
||
// this is a 2-dimensional array of integers
|
||
|
||
//Declaring variables
|
||
var
|
||
int, c, d : integer;
|
||
// three variables that contain integer numbers
|
||
// integers are 16-bits and limited to the range [-32,768..32,767]
|
||
r : real;
|
||
// a variable that contains a real number data types
|
||
// reals can range between [3.4E-38..3.4E38]
|
||
bool : boolean;
|
||
// a variable that contains a Boolean(True/False) value
|
||
ch : char;
|
||
// a variable that contains a character value
|
||
// char variables are stored as 8-bit data types so no UTF
|
||
str : string;
|
||
// a non-standard variable that contains a string value
|
||
// strings are an extension included in most Pascal compilers
|
||
// they are stored as an array of char with default length of 255.
|
||
s : string[50];
|
||
// a string with maximum length of 50 chars.
|
||
// you can specify the length of the string to minimize memory usage
|
||
my_str: ch_array;
|
||
// you can declare variables of custom types
|
||
my_2d : md_array;
|
||
// dynamically sized arrays need to be sized before they can be used.
|
||
|
||
// additional integer data types
|
||
b : byte; // range [0..255]
|
||
shi : shortint; // range [-128..127]
|
||
smi : smallint; // range [-32,768..32,767] (standard Integer)
|
||
w : word; // range [0..65,535]
|
||
li : longint; // range [-2,147,483,648..2,147,483,647]
|
||
lw : longword; // range [0..4,294,967,295]
|
||
c : cardinal; // longword
|
||
i64 : int64; // range [-9223372036854775808..9223372036854775807]
|
||
qw : qword; // range [0..18,446,744,073,709,551,615]
|
||
|
||
// additional real types
|
||
rr : real; // range depends on platform (i.e., 8-bit, 16-bit, etc.)
|
||
rs : single; // range [1.5E-45..3.4E38]
|
||
rd : double; // range [5.0E-324 .. 1.7E308]
|
||
re : extended; // range [1.9E-4932..1.1E4932]
|
||
rc : comp; // range [-2E64+1 .. 2E63-1]
|
||
|
||
Begin
|
||
int := 1;// how to assign a value to a variable
|
||
r := 3.14;
|
||
ch := 'a';
|
||
str := 'apple';
|
||
bool := true;
|
||
//pascal is not a case-sensitive language
|
||
//arithmetic operation
|
||
int := 1 + 1; // int = 2 overwriting the previous assignment
|
||
int := int + 1; // int = 2 + 1 = 3;
|
||
int := 4 div 2; //int = 2 division operation where result will be floored
|
||
int := 3 div 2; //int = 1
|
||
int := 1 div 2; //int = 0
|
||
|
||
bool := true or false; // bool = true
|
||
bool := false and true; // bool = false
|
||
bool := true xor true; // bool = false
|
||
|
||
r := 3 / 2; // a division operator for real
|
||
r := int; // can assign an integer to a real variable but not the reverse
|
||
|
||
c := str[1]; // assign the first letter of str to c
|
||
str := 'hello' + 'world'; //combining strings
|
||
|
||
my_str[0] := 'a'; // array assignment needs an index
|
||
|
||
setlength(my_2d,10,10); // initialize dynamically sized arrays: 10×10 array
|
||
for c := 0 to 9 do // arrays begin at 0 and end at length-1
|
||
for d := 0 to 9 do // for loop counters need to be declared variables
|
||
my_2d[c,d] := c * d;
|
||
// address multidimensional arrays with a single set of brackets
|
||
|
||
End.
|
||
```
|
||
|
||
```pascal
|
||
program Functional_Programming;
|
||
|
||
Var
|
||
i, dummy : integer;
|
||
|
||
function factorial_recursion(const a: integer) : integer;
|
||
{ recursively calculates the factorial of integer parameter a }
|
||
|
||
// Declare local variables within the function
|
||
// e.g.:
|
||
// Var
|
||
// local_a : integer;
|
||
|
||
Begin
|
||
If a >= 1 Then
|
||
// return values from functions by assigning a value to the function name
|
||
factorial_recursion := a * factorial_recursion(a-1)
|
||
Else
|
||
factorial_recursion := 1;
|
||
End; // terminate a function using a semicolon after the End statement.
|
||
|
||
procedure get_integer(var i : integer; dummy : integer);
|
||
{ get user input and store it in the integer parameter i.
|
||
parameters prefaced with 'var' are variable, meaning their value can change
|
||
outside of the parameter. Value parameters (without 'var') like 'dummy' are
|
||
static and changes made within the scope of the function/procedure do not
|
||
affect the variable passed as a parameter }
|
||
|
||
Begin
|
||
write('Enter an integer: ');
|
||
readln(i);
|
||
dummy := 4; // dummy will not change value outside of the procedure
|
||
End;
|
||
|
||
Begin // main program block
|
||
dummy := 3;
|
||
get_integer(i, dummy);
|
||
writeln(i, '! = ', factorial_recursion(i));
|
||
// outputs i!
|
||
writeln('dummy = ', dummy); // always outputs '3' since dummy is unchanged.
|
||
End.
|
||
|
||
```
|
||
|