number representation

This is a discussion on number representation within the C Programming forums, part of the General Programming Boards category; Hola! im new to C programming and taking some CS classes at the university. My instructor asked us to write ...

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    number representation

    Hola! im new to C programming and taking some CS classes at the university. My instructor asked us to write a C program to figure out what num notation is used by your machine... 1's, 2's complement or signed magnitude and I dont even know how to begin. Im not loking for code just ideas on how to do this.

    gracias

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    C++ Witch laserlight's Avatar
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    First, review your understanding of one's complement, two's complement, and sign and magnitude. Consider say, -1. Assuming an n-bit integer, what is the representation of -1 in each of these systems? Then, check the interesting bits of -1 to see which it corresponds to.
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    Quote Originally Posted by laserlight View Post
    First, review your understanding of one's complement, two's complement, and sign and magnitude. Consider say, -1. Assuming an n-bit integer, what is the representation of -1 in each of these systems? Then, check the interesting bits of -1 to see which it corresponds to.
    Hola! i know all 3 but dont know how to do it programaticaly. So por example if 4 bits then -1 will be 1111 in 2's complement and 1110 in 1's complement and 1001 in signed magnitude... correcto?

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    Yes. What I have in mind with this suggestion is the use of bitwise operators.
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    Quote Originally Posted by laserlight View Post
    Yes. What I have in mind with this suggestion is the use of bitwise operators.
    Do you mean << and >> operators... so how to do it with them.

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    Quote Originally Posted by fsanchez
    Do you mean << and >> operators... so how to do it with them.
    Yes, and also bitwise and. A tutorial on the topic should be enough to get you going, so just search the Web
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    Quote Originally Posted by laserlight View Post
    Yes, and also bitwise and. A tutorial on the topic should be enough to get you going, so just search the Web
    Muy bien i was able to come up with a program to find no. representation of machine but when i run it on several machines in my lab they all give ans of 2's complement. Now i suppose to explain why and here is code based on your sugestion.
    Code:
    #define NUMERO 0xF
    int main() {
            switch (-1&0xF) {
                    case NUMERO: printf("2's complement\n"); break;
                    case NUMERO-1: printf("1's complement\n"); break;
                    default: printf("signed magnitude\n"); break;
            }
    }

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