Pascal · Lesson 1 · On the house

Program structure

Program headers, begin/end blocks, writeln, compiler modes, and building with Free Pascal.

Lessons · Pascal · Lesson 1 of 10 · On the house

Program structure

Program headers, begin/end blocks, writeln, compiler modes, and building with Free Pascal.

Illustration for Pascal — Lesson 1 is on the house.

A Pascal program starts with program Name;, optional uses units, declarations, then a main block begin ... end. (note the final period).

writeln('text') prints a line, and write prints without a newline. Strings use single quotes. To put a quote inside one, double it: 'it''s'.

Free Pascal compiles with fpc hello.pas then ./hello. {$mode objfpc}{$H+} selects modern Object Pascal and long (AnsiString) strings. Most modern code uses it.

Pascal is case-insensitive. Statements are separated by ;.

Comments go in { ... } or (* ... *), or after // ... for the rest of the line.

hello

program Hello;
{$mode objfpc}{$H+}
begin
  writeln('Hello from Pascal');
  write('same ');
  write('line');
  writeln;
  writeln('it''s ', 3, ' items');
  WriteLn('case-insensitive');
end.

Match this when you type.

Quiz

What ends the main program block?

}
end.
end;
return

Quiz

How do you write a single quote inside a string?

\'
"'"
"
Double it: ''

Quiz

What does {$H+} change?

Hides warnings
string becomes a long AnsiString
Enables threads
Enables hex output

Quiz

Which call prints without a newline?

puts
print
writeln
write

Check

Match the still for: Program structure.

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