Code this in C and explain what the code of each function does please.

Bool IsDecimalInteger(char str[]); Description: The function takes a string (character array) and checks if it is a valid decimal representation of an integer number. Please note that using functions like atoi (...) from the Standard Library is not really helpful here since the actual (mathematical) integer number might be larger than the maximum possible value of the type unsigned long long int. Your function must not have any restriction on the integer values (the length of the string representation). If str represents an integer, the function must return 1. Otherwise - return O. Examples: str "23510" "-2319" "-2319" "25g17" 200-50 Return value 1 0 (extra spaces in front) 1 0 (non-digit inside) 0 (the function does not compute expressions; it simply checks if str represents an integer number or not) 0 (empty str 1 0 (this is a decimal representation of a real number, but not an integer number) 9999999999999999999999" "999999999999999999 "570.11" char GetSortingOrder (double arr[], size_t arr_size); Description: The function checks if the array arr (whose elements are of type double) is sorted (elements come in non-decreasing order: if i