The Structure of a Pascal Program in Java

Encoding QR-Code in Java The Structure of a Pascal Program

Although it s unlikely that Pascal will ever regain its popularity as a major programming language, Pascal has inspired other programming languages, most notably the Ada programming language, which is used in critical, realtime systems, such as the Boeing 777 avionics system As a result, Pascal remains an influential programming language to this day

The strength (or weakness, depending on your point of view) of Pascal is that it forces you to structure your programs At the beginning of a Pascal program, you must declare any constants, types, or variables, such as

Program name; Const (* Constants here *) Type (* Type definitions here *) Var (* Variable declarations here *) Begin (* Commands here *); End

A typical Pascal program might look like this:

Program TaxRefund; Const TaxRate = 035; Type ClassLevel = (Upper, Middle, Lower); Var MyClass : ClassLevel; TaxesOwed, Income : integer; Begin Income := 60000; TaxesOwed := Income * TaxRate; If MyClass = Upper then Begin Writeln ( Bribe a corrupt politician ); End; End

Pascal/Delphi allows you to enclose comments with curly brackets {} or a parentheses and an asterisk pair (* *), such as

Program name; (* This is a short Pascal program *) Begin {The Writeln command is used to display text on the screen, much like the Print command in other languages} Writeln ( This is a simple Pascal program ); End

In every Pascal/Delphi program, define a separate section for declaring your variables by using the Var keyword, such as

Program namehere; Var Variablename1 : datatype; Variablename2 : datatype; Begin (* Commands go here *) End

Unlike C/C++, Pascal isn t a case-sensitive language, so the variable names TaxRate, taxrate, and Taxrate are all considered the same variable

Strings represent text, such as a single character ( A ) or several words ( This is a string of text ) To declare a string variable, use the String keyword, such as

Var Variablename1 : String;

In Pascal, strings are enclosed in single quote marks (not double quote marks as in other languages) After you declare a variable to hold a string, you can assign a string to that variable, such as

Variablename1 := This string gets stored in the variable ;

Var Variablename1 : Char;

To assign values to a variable in Pascal, use the colon and the equal sign symbols, such as :=, instead of just the equal sign (=) like other programming languages

Whole numbers represent integers such as 349, 152, or 41 A whole number can be positive or negative The most common type of integer data type is Integer and is used as follows:

Var Variablename1 : Integer;

To accept different ranges of integer values, Pascal offers several integer data types For example, if a variable needs only to hold a positive value, you can declare it as a Byte data type, such as

Var Variablename1 : Byte;

Besides limiting the range of integer values, different integer data types also require different amounts of memory to store that data The greater the range of values you need to store, the more memory needed (measured in bytes) The smaller the range of values, the less memory required Table 4-1 shows different integer data types, the memory needed, and the range of values they can hold

Table 4-1

0 to 255 128 to 127 0 to 65,535 32,768 to 32,767 2,147,483,648 to 2,147,483,647 0 to 4,294,967,295 9,223,372,036,854,775,808 to 9,223,372,036,854,775,807

Decimal values are numbers such as 188 or 914 Just as you can limit the range of integer values a variable can hold, so can you limit the range of decimal values a variable can hold In Visual Basic, the four types of decimal data types are Single, Double, Currency, and Extended, as shown in Table 4-2