dbexport - Components that allow exporting datasets to RTF, simple XML, TeX, DBF, JSON, SQL statements, fixed format text files, CSV files, and more formats:.datetimectrls - This package contains TDateTimePicker control and TDBDateTimePicker (a data aware version of TDateTimePicker).daemon - Creating background applications.customdrawn - An under construction package containing all kinds of custom drawn components for Lazarus.chmhelp - Provides context-sensitive help for the IDE using CHM files. Mouseandkeyinput in free pascal code#Note that there are also other components which can be downloaded separately from the Lazarus Code and Component Repository. Free Pascal provides the following functions and procedure for memory management: S.The "components" directory of the Lazarus source tree comes with a number of very useful components, and they are described below. Many of these functions are implementation dependent. Pascal provides a hoard of memory management functions that is used in implementing various data structures and implementing low level programming in Pascal. Following is the syntax for ReAllocMem: functionReAllocMem ( var p : pointer Size :PtrUInt ) : pointer įollowing is an example which makes use of ReAllocMem and freemem subprograms: program exMemory varĭescription : = getmem ( 30 ) if not assigned (description ) then writeln ( 'Error - unable to allocate required memory' ) elseĭescription ^ : = desp (*Suppose you want to store bigger description *)ĭescription : = reallocmem (description, 100 ) ĭesp : = desp + ' She is in class 10th.' ĭescription ^ : = desp writeln ( 'Name = ', name ) writeln ( 'Description: ', description ^ ) freemem (description ) ĭescription: Zara ali a DPS student. Let us check the above program once again and make use of ReAllocMem and freemem subprograms. The freemem subprograms have the following syntax: procedure Freemem (p : pointer Size :PtrUInt ) function Freemem (p : pointer ) :PtrUInt Īlternatively, you can increase or decrease the size of an allocated memory block by calling the function ReAllocMem. If you have allocated memory using the getmemsubprogram, then you need to use the subprogram freemem to free this memory. Pascal provides the procedure dispose to free a dynamically created variable using the procedure new. When your program comes out, operating system automatically release 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. So you have complete control and you can pass any size value while allocating memory unlike arrays where once you defined the size cannot be changed. Let us rewrite the previous example, using getmem: program exMemory varĭescription : = getmem ( 200 ) if not assigned (description ) then writeln ( ' Error - unable to allocate required memory' ) elseĭescription ^ : = 'Zara ali a DPS student in class 10th' writeln ( 'Name = ', name ) writeln ( 'Description: ', description ^ ) freemem (description ) If you really don't need that much space, or a larger space, in terms of bytes, getmem subprogram allows specifying that. A string has a maximum value of 255 bytes. In the previous example, we declared a pointer to a string. Now, if you need to define a pointer with specific number of bytes to be referred by it later, you should use the getmem function or the getmem procedure, which has the following syntax: procedure Getmem (out p : pointer Size :PtrUInt ) function GetMem (size :PtrUInt ) : pointer When the above code is compiled and executed, it produces following result: Name = Zara Aliĭescription: Zara ali a DPS student in class 10th Name : = 'Zara Ali' new (description ) if not assigned (description ) then writeln ( ' Error - unable to allocate required memory' ) elseĭescription ^ : = 'Zara ali a DPS student in class 10th' writeln ( 'Name = ', name ) writeln ( 'Description: ', description ^ ) Pascal provides a procedure new to create pointer variables. Here we need to define a pointer to string without defining how much memory is required. For example to store a name of any person, it can go max 100 characters so you can define something as follows: varīut now let us consider a situation where you have no idea about the length of the text you need to store, for example you want to store a detailed description about a topic. While doing programming, if you are aware about the size of an array, then it is easy and you can define it as an array. Pascal programming language provides several functions for memory allocation and management. This chapter explains dynamic memory management in Pascal.
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