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    <p>Of course the others are (generally) correct. What wasn't said, is that 'i' in your loop <strong><em>doesn't</em></strong> exist. Delphi uses a CPU register for it. That's why you cannot change it and that's why you should use a 'for' loop (not a 'while') because the 'for' is way faster. Here is your code modified (not tested but I think that you got the idea) - also imho you had some bugs - fixed them also:</p> <pre><code>function Check(var MemoryData:Array of byte;MemorySignature:Array of byte;Position:integer):boolean; var i:byte; begin Result := True; //moved at top. Your function always returned 'True'. This is what you wanted? for i := 0 to Length(MemorySignature) - 1 do //are you sure??? Perhaps you want High(MemorySignature) here... begin if MemorySignature[i] &lt;&gt; $FF then //speedup - '&lt;&gt;' evaluates faster than '=' begin Result:=memorydata[i + position] &lt;&gt; MemorySignature[i]; //speedup. if not Result then Break; //added this! - speedup. We already know the result. So, no need to scan till end. end; end; end; </code></pre> <p>...also MemorySignature should have a 'const' or 'var'. Otherwise as it is now the array gets copied. Which means slowdown at each call of 'Check'. Having a 'var' the things are much faster with code unchanged because AFAIS the MemorySignature isn't changed.</p> <p>HTH</p>
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    1. POHow to increase the FOR-loop value in a FOR-loop statement?
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    1. USJohn Thomas
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    1. POHow to increase the FOR-loop value in a FOR-loop statement?
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    1. COHey,thanks,I leant very much from your code!I have two questions.Why "Break;" instead of "Exit;"? and When should I use "var" as a function parameter,I couldn't find a useful explanation and you must have at least two I guess!
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      1. USIvan Prodanov
    2. CO'Break' means "Out of the current LOOP" (for etc.) while 'Exit' means "Out of the current CODE BLOCK" (procedure/function etc.). In our concrete case, yes, *is* the same but (imho) is a good coding habbit to terminate the function at the final 'end'. Of course this is a general rule, not a dogma. Let's suppose that someone else takes the code and he decides that after each check he must wipe (IOW fill with #$00) the MemorySignature, regardless of the function's result. Instinctually he'll add a 'for' loop at the end. If there is an 'Exit' in the middle, then that code *sometimes* is skiped.
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      1. USJohn Thomas
    3. COThere are some ways to pass the parameters. The default one is by value: s:='Foo'; MyFunc(s); Write(s); will write 'Foo' regardless of what is happening inside of MyFunc and this is because 's' is get **copied** inside of the function (in order to protect the 'outside s' from the changes which happen inside of MyFunc) and if 's' is big (many kB) then this can be expensive. Adding a 'var' there, means that _only_ the pointer to 's' (the reference to 's') is passed which is way faster (only few bytes) but this means that any changes which happen inside of your func will be 'visible' outside.
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