Multiple assignment in one line

Question

I just come across the statement in embedded c (dsPIC33)

sample1 = sample2 = 0;

Would this mean

sample1 = 0;

sample2 = 0;
         


        

Answer 1

As noticed earlier,

sample1 = sample2 = 0;

is equal to

sample2 = 0;
sample1 = sample2;

The problem is that riscy asked about embedded c, which is often used to drive registers directly. Many of microcontroller's registers have a different purpose on read and write operations. So, in gereral case, it is not the same, as

sample2 = 0;
sample1 = 0;

For example, let UDR be a UART data register. Reading from UDR means getting the recieved value from the input buffer, while writing to UDR means putting the desired value into transmit buffer and hitting the communication. In that case,

sample = UDR = 0;

means the following: a) transmit value of zero using UART (UDR = 0;) and b) read input buffer and place data into sample value (sample = UDR;).

You could see, the behavior of embedded system could be much more complicated than the code writer may expect to be. Use this notation carefully while programming MCUs.