Value bigger than the signed value

The program is a bigger program but the summary of program is

Code:

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int main(void)
{
signed int data1;
data1 = 32785;
return 0;
}

---

I know that data1 is signed value and hence the maximum value is 32767. When i store 32785 will the value of data1 be 32767-32785 = -18? But the correct value is -32751. How was it arrived? Please help.

Lots of things going on here, but in summary, if 'int' is 16 bits, and you have a overflow the answer will be wrong by 2^16, or 65536.

So what is 32785-65536? −32,751

Thank you for the reply. The complete program is

Code:

---

uint32_t startupRamp=0;
int16_t theta=0;
void CalculateTheta(void)
{
    /* Then ramp up till the end */
    if (startupRamp < END_SPEED)
    {
        startupRamp += 10;
    }
    theta += (int16_t)(startupRamp >> 10);
}

---

So my understanding and sequence of steps are
a. When startupRamp is 32785, its hex value is 0x8011.
b. The MSBit is 1 hence it is negative value.
c. Compiler will store the 2's complement number is 32751.
d. The computer will add a negative sign (since the MSBit is 1) and assign the value of -32751. Is it correct? Please help.

Quote:

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Originally Posted by CTest123

Thank you for the reply. The complete program is

Code:

---

uint32_t startupRamp=0;
int16_t theta=0;
void CalculateTheta(void)
{
    /* Then ramp up till the end */
    if (startupRamp < END_SPEED)
    {
        startupRamp += 10;
    }
    theta += (int16_t)(startupRamp >> 10);
}

---

So my understanding and sequence of steps are
a. When startupRamp is 32785, its hex value is 0x8011.
b. The MSBit is 1 hence it is negative value.
c. Compiler will store the 2's complement number is 32751.
d. The computer will add a negative sign (since the MSBit is 1) and assign the value of -32751. Is it correct? Please help.

---

It's way easier than that. For 16-bit signed numbers the most significant bit has a 'place value' of -32768, rather than the 32768 it would have in an unsigned (or longer) value.

So 0x8011 as a 16-bit unsigned decimal = 32768+1*16+1 = 32785
and 0x8011 as a 16-bit signed decimal = -32768+1*16+1 = -32751

Thank you that is really helpful.