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Resizing and Releasing Memory When your program comes out, operating system automatically releases all the memory allocated by your program, but as a good practice when you are not in need of memory anymore, then you should release that memory. Pascal provides the procedure dispose to free a dynamically created variable using the procedure new. If you have allocated memory using the getmem subprogram, then you need to use the subprogram freemem to free this memory. The freemem subprograms have the following syntax: procedure Freemem( p: pointer; Size: PtrUInt ); function Freemem( p: pointer ):PtrUInt; Alternatively, you can increase or decrease the size of an allocated memory block by calling the function ReAllocMem. Let us check the above program once again and make use of ReAllocMem and freemem subprograms. Following is the syntax for ReAllocMem: function ReAllocMem( var p: pointer; Size: PtrUInt ):pointer; Following is an example which makes use of ReAllocMem and freemem subprograms: program exMemory; var name: array[1..100] of char; description: ^string; desp: string; begin name:= 'Zara Ali'; desp := 'Zara ali a DPS student.'; description := getmem(30); if not assigned(description) then writeln('Error - unable to allocate required memory') else description^ := desp; (* Suppose you want to store bigger description *) description := reallocmem(description, 100); desp := desp + ' She is in class 10th.'; description^:= desp; writeln('Name = ', name ); writeln('Description: ', description^ ); freemem(description); end. TUTORIALS POINT Simply Easy Learning Page 126
Name = Zara Ali Description: Zara ali a DPS student. She is in class 10 th When the above code is compiled and executed, it produces the following result: Name = Zara Ali Description: Zara ali a DPS student. She is in class 10th Memory Management Functions Pascal provides a hoard of memory management functions that is used in implementing various data structures and implementing low-level programming in Pascal. Many of these functions are implementation dependent. Free Pascal provides the following functions and procedures for memory management: S.N. Function Name & Description 1 function Addr(X: TAnytype):Pointer; Returns address of variable 2 function Assigned(P: Pointer):Boolean; Checks if a pointer is valid 3 function CompareByte(const buf1; const buf2; len: SizeInt):SizeInt; Compares 2 memory buffers byte per byte 4 function CompareChar(const buf1; const buf2; len: SizeInt):SizeInt; Compares 2 memory buffers byte per byte 5 function CompareDWord(const buf1; const buf2; len: SizeInt):SizeInt; Compares 2 memory buffers byte per byte 6 function CompareWord(const buf1; const buf2; len: SizeInt):SizeInt; Compares 2 memory buffers byte per byte 7 function Cseg: Word; Returns code segment 8 procedure Dispose(P: Pointer); Frees dynamically allocated memory 9 procedure Dispose(P: TypedPointer; Des: TProcedure); TUTORIALS POINT Simply Easy Learning Page 127
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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
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Pascal programming language also al
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Enumerated Variables You have seen
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CHAPTER 7 Constants This section sh
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CHAPTER 8 Operators This section sh
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Checks if the value of left operand
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When the above code is compiled and
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program beBitwise; var a, b, c: int
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CHAPTER 9 Decision Making This sect
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Example: Let us try a complete exam
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Example: Let us try a complete exam
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Nested if-then Statements It is alw
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The following rules apply to a case
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Flow Diagram: Example: The followin
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CHAPTER 10 Loops This section shows
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Flow Diagram: Here, key point of th
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Flow Diagram Example: program forLo
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Example: program repeatUntilLoop; v
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Example: program exBreak; var a: in
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Example: program exContinue; var a:
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Example: The following program illu
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Defining a Function: In Pascal, a f
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variable named m. The variable m is
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program exRecursion; var num, f: in
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procedure swap(x, y: integer); var
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Now, let us extend the program litt
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Let us change the previous example
Page 83 and 84: When the above code is compiled and
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
Page 128 and 129: Reads data from a file into memory
Page 130 and 131: Reads from file into variable and g
Page 132 and 133: CHAPTER 22 Memory Management This s
Page 136 and 137: Frees dynamically allocated memory
Page 138 and 139: Returns segment 37 procedure SetMem
Page 140 and 141: eadkey; clrscr; gotoxy(20,3); write
Page 144 and 145: Program DateDemo; uses sysutils; va
Page 146 and 147: 14 function EncodeDate( Year: Word;
Page 148 and 149: 39 function TimeStampToDateTime( co
Page 150 and 151: Objects This section shows the conc
Page 152 and 153: type Rectangle = object private len
Page 156 and 157: egin r1.init(3, 7); writeln('Draw a
Page 158 and 159: function TableTop.getmaterial(): st
Page 160 and 161: Classes This section shows the clas
Page 162 and 163: {$mode objfpc} // directive to be u
Page 164 and 165: Constructors and Destructors for Pa
Page 166 and 167: program inheritanceExample; {$MODE
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