[Sawalha]

sscanf returns 0 when succeed, and 1 when failed,

Код:

if(sscanf(params, "rd", id, dif))
{

the code under this statement is called when a failure occurs of sscanf function here.

the code under else { is called when sscanf returns 0 (success)

so, to check if sccanf succeed, which means it returned 0:

Код:

if(!sscanf(params, "Rd", id, dif))

that means if the function sscanf returned a zero, and without the NOT operator ("!") it means if the function returned another value higher than zero