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CHAPTER 6 Variable Types This section shows the variable types used in a Pascal program. A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in Pascal has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable. The name of a variable can be composed of letters, digits, and the underscore character. It must begin with either a letter or an underscore. Pascal is not case-sensitive, so uppercase and lowercase letters mean same here. Based on the basic types explained in previous chapter, there will be following basic variable types: Basic Variables in Pascal Type Character Integer Real Boolean Enumerated Subrange String Description Typically a single octet (one byte). This is an integer type. The most natural size of integer for the machine. A single-precision floating point value. Specifies true or false logical values. This is also an integer type. Specifies a user-defined list. Represents variables, whose values lie within a range. Stores an array of characters. TUTORIALS POINT Simply Easy Learning Page 16
Pascal programming language also allows defining various other types of variables, which we will cover in subsequent chapters like <strong>Point</strong>er, Array, Records, Sets, and Files, etc. For this chapter, let us study only basic variable types. Variable Declaration in Pascal All variables must be declared before we use them in Pascal program. All variable declarations are followed by the var keyword. A declaration specifies a list of variables, followed by a colon (:) and the type. Syntax of variable declaration is: var variable_list : type; Here, type must be a valid Pascal data type including character, integer, real, boolean, or any user-defined data type, etc., and variable_list may consist of one or more identifier names separated by commas. Some valid variable declarations are shown here: var age, weekdays : integer; taxrate, net_income: real; choice, isready: boolean; initials, grade: char; name, surname : string; In the previous <strong>tutorial</strong>, we have discussed that Pascal allows declaring a type. A type can be identified by a name or identifier. This type can be used to define variables of that type. For example: type days, age = integer; yes, true = boolean; fees, expenses = real; Now, the types so defined can be used in variable declarations: var weekdays, holidays : days; choice: yes; student_name, emp_name : name; capital: city; cost: expenses; Please note the difference between type declaration and var declaration. Type declaration indicates the category or class of the types such as integer, real, etc., whereas the variable specification indicates the type of values a variable may take. You can compare type declaration in Pascal with typedef in C. Most importantly, the variable name refers to the memory location where the value of the variable is going to be stored. This is not so with the type declaration. TUTORIALS POINT Simply Easy Learning Page 17
Page 1 and 2: Pascal Tutorial
Page 3 and 4: ABOUT THE TUTORIAL Pascal Tutorial
Page 5 and 6: Declaring Constants ...............
Page 7 and 8: Accessing Two-Dimensional Array Ele
Page 9 and 10: CHAPTER 1 Pascal Overview This chap
Page 11 and 12: CHAPTER 2 Environment This section
Page 13 and 14: Name and version of text editor can
Page 15 and 16: Pascal Hello World Example Followin
Page 17 and 18: CHAPTER 4 Basic Syntax You have see
Page 19 and 20: The Pascal character set consists o
Page 21 and 22: Type Declarations: The type declara
Page 23: Subrange Types Subrange types allow
Page 27 and 28: Enumerated Variables You have seen
Page 29 and 30: CHAPTER 7 Constants This section sh
Page 31 and 32: CHAPTER 8 Operators This section sh
Page 33 and 34: Checks if the value of left operand
Page 35 and 36: When the above code is compiled and
Page 37 and 38: program beBitwise; var a, b, c: int
Page 39 and 40: CHAPTER 9 Decision Making This sect
Page 41 and 42: Example: Let us try a complete exam
Page 43 and 44: Example: Let us try a complete exam
Page 45 and 46: Nested if-then Statements It is alw
Page 47 and 48: The following rules apply to a case
Page 49 and 50: Flow Diagram: Example: The followin
Page 51 and 52: CHAPTER 10 Loops This section shows
Page 53 and 54: Flow Diagram: Here, key point of th
Page 55 and 56: Flow Diagram Example: program forLo
Page 57 and 58: Example: program repeatUntilLoop; v
Page 61 and 62: Example: program exBreak; var a: in
Page 63 and 64: Example: program exContinue; var a:
Page 65 and 66: Example: The following program illu
Page 67 and 68: Defining a Function: In Pascal, a f
Page 71 and 72: variable named m. The variable m is
Page 73 and 74: program exRecursion; var num, f: in
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procedure swap(x, y: integer); var
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When the above code is compiled and
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Now, let us extend the program litt
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Let us change the previous example
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12 function AnsiStrLower( Str: PCha
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CHAPTER 15 Boolean This section sho
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CHAPTER 16 Arrays This section show
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Initializing Arrays In Pascal, arra
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Two-Dimensional Arrays: The simples
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The following example declares and
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Passing Arrays as Subprogram Argume
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Following are some valid pointer de
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To check for a nil pointer, you can
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program exPointers; const MAX = 3;
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program exPointers; const MAX = 3;
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Value of num = 3000 Value available
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CHAPTER 18 Records This section sho
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(* book 2 specification *) Book2.ti
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type record-ptr = ^ record-name; re
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(* book 1 specification *) Book1.ti
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Example: The following example woul
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Set Operators You can perform the f
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CHAPTER 21 File Handling This secti
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Reads data from a file into memory
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Reads from file into variable and g
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CHAPTER 22 Memory Management This s
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Resizing and Releasing Memory When
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Frees dynamically allocated memory
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Returns segment 37 procedure SetMem
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eadkey; clrscr; gotoxy(20,3); write
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Program DateDemo; uses sysutils; va
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14 function EncodeDate( Year: Word;
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39 function TimeStampToDateTime( co
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Objects This section shows the conc
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type Rectangle = object private len
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egin r1.init(3, 7); writeln('Draw a
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function TableTop.getmaterial(): st
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Classes This section shows the clas
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{$mode objfpc} // directive to be u
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Constructors and Destructors for Pa
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program inheritanceExample; {$MODE
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