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Call by Reference The call by reference method of passing arguments to a subprogram copies the address of an argument into the formal parameter. Inside the subprogram, the address is used to access the actual argument used in the call. This means that changes made to the parameter affect the passed argument. In order to pass the arguments by reference, Pascal allows to define variable parameters. This is done by preceding the formal parameters by the keyword var. Let us take the example of the procedure swap() that swaps the values in two variables and reflect the change in the calling subprogram. procedure swap(var x, y: integer); var temp: integer; begin temp := x; x:= y; y := temp; end; Next, let us call the procedure swap() by passing values by reference as in the following example: program exCallbyRef; var a, b : integer; (*procedure definition *) procedure swap(var x, y: integer); var temp: integer; begin temp := x; x:= y; y := temp; end; begin a := 100; b := 200; writeln('Before swap, value of a : ', a ); writeln('Before swap, value of b : ', b ); (* calling the procedure swap by value *) swap(a, b); writeln('After swap, value of a : ', a ); writeln('After swap, value of b : ', b ); end. TUTORIALS POINT Simply Easy Learning Page 68
When the above code is compiled and executed, it produces the following result: Before swap, value of a : 100 Before swap, value of b : 200 After swap, value of a : 200 After swap, value of b : 100 Which shows that now the procedure swap() has changed the values in the calling program. TUTORIALS POINT Simply Easy Learning Page 69
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Pascal Tutorial
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ABOUT THE TUTORIAL Pascal Tutorial
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Declaring Constants ...............
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Accessing Two-Dimensional Array Ele
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CHAPTER 1 Pascal Overview This chap
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CHAPTER 2 Environment This section
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Name and version of text editor can
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Pascal Hello World Example Followin
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CHAPTER 4 Basic Syntax You have see
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The Pascal character set consists o
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Type Declarations: The type declara
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Subrange Types Subrange types allow
Page 25 and 26: Pascal programming language also al
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
Page 75: procedure swap(x, y: integer); var
Page 79 and 80: Now, let us extend the program litt
Page 81 and 82: Let us change the previous example
Page 85 and 86: 12 function AnsiStrLower( Str: PCha
Page 87 and 88: CHAPTER 15 Boolean This section sho
Page 89 and 90: CHAPTER 16 Arrays This section show
Page 91 and 92: Initializing Arrays In Pascal, arra
Page 93 and 94: Two-Dimensional Arrays: The simples
Page 95 and 96: The following example declares and
Page 97 and 98: Passing Arrays as Subprogram Argume
Page 99 and 100: Following are some valid pointer de
Page 101 and 102: To check for a nil pointer, you can
Page 103 and 104: program exPointers; const MAX = 3;
Page 105 and 106: program exPointers; const MAX = 3;
Page 107 and 108: Value of num = 3000 Value available
Page 109 and 110: CHAPTER 18 Records This section sho
Page 111 and 112: (* book 2 specification *) Book2.ti
Page 113 and 114: type record-ptr = ^ record-name; re
Page 115 and 116: (* book 1 specification *) Book1.ti
Page 117 and 118: Example: The following example woul
Page 119: Set Operators You can perform the f
Page 122 and 123: CHAPTER 21 File Handling This secti
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When the above code is compiled and
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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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