Absolute

From Free Pascal wiki
Revision as of 03:51, 19 September 2017 by FPC user (talk | contribs) (note little endian)

Deutsch (de) English (en) español (es) suomi (fi) français (fr) русский (ru)

The absolute modifier causes a variable to be stored at the same memory location as another variable.


// Example on little endian x64 processor
Uses SysUtils;

Var
    anInt      : Integer;
    anotherInt : Integer absolute anInt;
    firstByte  : Byte absolute anInt;
 
begin
    // with both Integer variables at the same memory location, a change to one is reflected
    // in the other
    anInt := 20;
    WriteLn(IntToStr(anInt) + '  ' + IntToStr(anotherInt)); // Outputs: 20  20

    // a value of 20 fits in the first byte:
    WriteLn('firstByte: ' + IntToStr(firstByte)); // Outputs: firstByte: 20
   
    anotherInt := 333;
    WriteLn(IntToStr(anInt) + '  ' + IntToStr(anotherInt)); // Outputs: 333 333

    // 333 is too large a value to fit in one byte
    // little-endian x64 - least significant byte is first in memory:
    // 333 = 101001101 =  01001101 00000001 = 0x4D 0x01 = decimal: 77 1
    WriteLn('firstByte: ' + IntToStr(firstByte)); // Outputs: firstByte: 77
end.