Chapter 11: Appendix

This appendix collects reference material for Pascal programming: a list of reserved words, some common compiler directives, and tips and best practices for writing efficient, maintainable Pascal code.

Pascal reserved words

Reserved words are predefined, so you can’t use them as identifiers such as variable or procedure names. Here is a list of them:

and         array       begin       case        const
div         do          downto      else        end
file        for         function    goto        if
in          label       mod         nil         not
of          or          packed      procedure   program
record      repeat      set         then        to
type        until       var         while       with

Common compiler directives

Compiler directives are special instructions that change how the compiler behaves.

Syntax

A compiler directive is usually written between {$ and }.

Examples

• $I includes a file.

  {$I filename.inc}
  

• $R turns range checking on or off.

  {$R+}  { Enable range checking }
  {$R-}  { Disable range checking }
  

• $Q does the same for overflow checking.

  {$Q+}  { Enable overflow checking }
  {$Q-}  { Disable overflow checking }
  

• $M sets the stack and heap sizes.

  {$M 16384,0,655360}
  

• $DEFINE and $UNDEF define and undefine symbols.

  {$DEFINE DEBUG}
  {$UNDEF DEBUG}
  

Tips and best practices

Use meaningful variable names

Descriptive names for variables, procedures, functions, and other identifiers make your code easier to read and maintain.

var
  totalAmount: real;
  studentName: string;

Comment your code

Use comments to explain what your code is for, especially where the logic is complex. They help other people (and you) understand it.

{ Calculate the total amount after applying the discount }
totalAmount := price - (price * discount / 100);

Consistent indentation

Indent your code consistently so it’s easier to read. Two or four spaces per level of indentation is typical.

if condition then
begin
  statement1;
  statement2;
end;

Avoid magic numbers

Instead of hard-coded numbers (magic numbers), use constants with meaningful names.

const
  MaxStudents = 50;

var
  studentCount: integer;

begin
  if studentCount > MaxStudents then
    writeln('Error: Exceeds maximum number of students');
end;

Modularize your code

Break your code into smaller, reusable procedures and functions. Modular code like this is easier to test and maintain.

procedure PrintGreeting(name: string);
begin
  writeln('Hello, ', name);
end;

begin
  PrintGreeting('Alice');
end.

Handle errors gracefully

Use error handling to deal with exceptions and other unexpected situations in your code.

try
  result := StrToInt(input);
except
  on E: EConvertError do
    writeln('Invalid number format');
end;

Optimize for performance

Avoid unnecessary calculations, and choose efficient algorithms and data structures.

for i := 1 to n do
  result := result + values[i];

Test your code thoroughly

Test with both normal and edge cases to make sure your code works correctly in every situation.

procedure TestAddition;
begin
  Assert(Add(2, 2) = 4);
  Assert(Add(-1, 1) = 0);
  Assert(Add(0, 0) = 0);
end;