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multipy function

Hsu YungSheng

Hi All
I am trying multipy function.After compliering, the a value is 0x78H, b is 0x02H. So, if I want addition function d=a+b(0x78+0x02H)to next line, how define variable a,b to get through with my request.

void main(void)
{
while(1){
char a,b,c,d;
a=0x9e;
b=0x04;
c=a*b; //a=0x78 b=0x02
d=a+b; //this line is 0x9e+0x04
}
}

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  • 0

    What is your problem here? What are you actually trying to achieve?

    Why can't you just write

    d = a + b*(0x78+0x02)
    Note 1: the compiler will actually evaluate the constant expression (0x78+0x02) at compile time.

    Note 2: your code effectively does nothing, as the value of d is never used - therefore the compiler may well optimise it out completely!

    Note 3: It is very likely that the result of the multiplication will be too big for a char - so you will be getting overflow!

Reply
  • 0

    What is your problem here? What are you actually trying to achieve?

    Why can't you just write

    d = a + b*(0x78+0x02)
    Note 1: the compiler will actually evaluate the constant expression (0x78+0x02) at compile time.

    Note 2: your code effectively does nothing, as the value of d is never used - therefore the compiler may well optimise it out completely!

    Note 3: It is very likely that the result of the multiplication will be too big for a char - so you will be getting overflow!

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