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Preparation
Lesson One - Sample Program
Lesson Two - Program Structure
Lesson Three - Data Types
and Constants
Lesson Four - Variables
Lesson Five - Text I/O
Lesson Six - Subroutines
Lesson Seven - Conditional
Statements
Lesson Eight - Arrays
Lesson Nine - Loops
Lesson Ten - Units
| | Lesson Three - Data Types and Constants
In pascal, you have a number of different ways to store data. In short, you can store it as a number, as text, as binary data, or any combination of the three. You should become familiar with the basic data types.
Numerical Types
Text/Character Types
Binary Types
| Numbers |
| Data Type | Bytes | Number type | Range |
| byte | 1 | integer | 0..255 |
| shortint | 1 | integer | -127..128 |
| word | 2 | integer | 0..65535 |
| smallint | 2 | integer | -32767..32768 |
| longword | 4 | integer | 0..4294967295 |
| longint | 4 | integer | -2147483648 .. 2147483647 |
| qword | 8 | integer | 0 .. 18446744073709551615 |
| int64 | 8 | integer | -9223372036854775808 .. 9223372036854775807 |
| integer | 2, 4 or 8 | integer | same as smallint, longint or int64 |
| cardinal | 2, 4 or 8 | integer | same as word, longword or qword |
| real | 4 or 8 | floating point | system dependent |
| single | 4 | floating point | 1.5E-45 .. 3.4E38, 7-8 significant digits |
| double | 8 | floating point | 5.0E-324 .. 1.7E308, 15-16 significant digits |
| extended | 10 | floating point | 1.9E-4951 .. 1.1E4932, 19-20 significant digits |
| comp | 8 | floating point | -2E64+1 .. 2E63-1, 19-20 significant digits |
| currency | 8 | fixed point | -922337203685477.5808..922337203685477.5807 (fixed at 4 digits < 1) |
As you can see, there are a LOT of different ways to describe numbers. In general, if you need an integer, use the integer type. The compiler will automatically decide which size integer to use. If you need a floating point number, you'll need to determine the largest number it should hold, and select your type based off of that. You should become accustomed to this method for selecting your data types.
| Text and Characters |
| Data Type | Size in bytes | Description |
| char | 1 | Stores a single ASCII character. i.e. 'a' |
| string[size] | size | Also known as a shortstring. This is the original Pascal string. It works as an array of characters, with the length of the actual string stored in varname[0]. |
| string | variable | The current default string type is a dynamically allocated array of characters. To get or change the length, use the Length and SetLength procedures. See Lesson 8 for more information on dynamic arrays. |
| widestring | variable | Same as string, but in Unicode format - that means that each character now takes twice as much space. It also allows you to create multi-lingual applications, since Unicode is required for many international characters. |
| pchar | 4+size of string | pchar is a pointer to a null terminated string. This is useful when working with routines written in other languages, such as C. |
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