Learning structure [Record] type (4)-structure pointer

Unit unit1; interfaceuses windows, messages, sysutils, variants, classes, graphics, controls, forms, dialogs, stdctrls; Type tform1 = Class (tform) button1: tbutton; button2: tbutton; button3: tbutton; button4: tbutton; Procedure submit (Sender: tobject ); end; var form1: tform 1; implementation {$ R *. DFM} type TREC = record {definition structure TREC} Name: String [12]; age: word; end; tprec = ^ TREC; {pointer type tprec} var REC: TREC; {declared Structure Variable} prec1, prec2: tprec; {declared tprec pointer variable} prec3: ^ TREC; {declare the pointer variable of the TREC structure. Now prec1 and prec3 are different types of variables} p: pointer; {declare No type pointer} // access the structure procedure tform1.button1click (Sender: tobject); begin rec. name: = 'zhang san'; Rec. age: = 18; prec1: = @ REC; {tell prec1 the REC address.} {Should have accessed} showmessage (prec1 ^. name); {zhangsan} {Delphi allows the simple use of the structure pointer} showmessage (prec1.name); {zhangsan} {if we modified the data through the pointer} prec1.name: = 'lily '; {so} showmessage (Rec. name); {Li Si} {because prec1 and REC refer to the same data} end; // if you use a pointer separately, you must first give the memory procedure tform1.button2click (Sender: tobject ); begin getmem (prec2, sizeof (TREC); prec2.name: = '王'; prec2.age: = 9; showmessage (prec2.name); {} {manual memory, must be manually released} freemem (prec2); end ;// Although a pointer of the same structure, procedure tform1.button3click (Sender: tobject); begin rec. name: = 'Sun 6'; Rec. age: = 16; {give the REC address to the prec3 pointer of the ^ rec type} prec3: = @ REC; showmessage (prec3.name ); {sun 6} {If You Want To Tell prec1 the value that prec3 knows, type conversion is required} prec1: = tprec (prec3); showmessage (prec1.name); {sun 6} {in turn, what if I want to tell prec3 the value that prec1 knows ?} Rec. name: = 'zhao 7'; Rec. age: = 24; prec1: = @ REC; showmessage (prec1.name); {Zhao Qi} {convert like this} tprec (prec3): = prec1; showmessage (prec3.name ); {Zhao Qi} end; // read and write data procedure tform1.button4click (Sender: tobject); begin rec. name: = 'duba '; Rec. age: = 36; P: = @ REC; {value assignment} tprec (P ). name: = 'hou jiu'; {value} showmessage (tprec (P ). name); {Hou JIU} end; end.