RAM Diagram for beginers.
BlitzPlus Forums/BlitzPlus Programming/RAM Diagram for beginers.
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| ello all. I've been keeping myself busying using all the information and that I've researched into making this diagram.  As you can see from it, it's a 24 byte RAM 7 bytes being taken up by a string of six bytes one byte being a NULL for end of string. What I would like to know is how a integer is stored, I remember in my old college course, my programming teacher telling me that an integer ranges from 0 to 32767. I unstand that using one byte I can have an integer from 0 to 255 but in programming that would be of little us in any program. So how do I make an integer number bigger using more bytes? Thank you all for helping me to get this far in understand memory storage. |
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| Your teacher should have said that an unsigned integer (always positive) is 0 to 65535 which is 2 bytes. A high byte and a low byte. If it is signed, the first bit is set to 1 to indicate that the number is negative so a signed integer can be from -32768 to 32767. These days integers are 32 bits and can be over 4 billion (unsigned) or 2 billion (signed). |
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| Well now I understand that two bytes 256*256 equals 65536 as an unsigned integer, but how do you get -32767 to 32767 using a signed integer? Plus this new concept of signed and unsigned I'll need to look into, not sure what it really means. Which could be why I'm struggling to understand. |
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| That's actually -32768 to +32767. Imagine you have a 3-digit odometer in your car. It can hold numbers 000 to 999. What if you wanted to treat some of these as negative? Well, starting at 999 and driving 1 more will produce 000. In odometer arithmetic 999 + 1 = 0. So you could reasonably consider that 999 represents -1. Likewise 998 + 2 = 0 so 998 represents -2, etc. In this way 000 to 499 may be considered positive and 500 to 999 are negative. It's the same with binary. The 'lower half' are positive. |
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 Thanks guys, I've learnt what unsigned integers are, just need to learn signed integers. Always with the learning. :D |
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| no wait, Floyd *was* explaining "signed" integers! |
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| I know. |
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| oh ok :-) |
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| Usually you use the Highest bit to denote whether it is negative or positive. But binary math either way is the same. Mathworld has everything you need to know. http://mathworld.wolfram.com/Binary.html |
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| Yeah, %11111111 is -128 and %01111111 is +127. Thats a signed byte. Just think of the first 7 bits as holding the number and the last bit as telling wether its positive or negative. |
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| %11111111 is -1. Adding 1 to it 'rolls over' to zero, as in my odometer analogy. |
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No, not with 2nd's Compliment |
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