Programming exercise 4 (24 points): the objective is to write a program that implements the function readhexbyte to input from the keyboard a byte (i. e., two digits) and store it in the register al. you must write the program to implement the function readhexbyte. in order to achieve this, you must read consecutively two decimal digits from the keyboard (use readchar for each digit). we assume that the user will enter only two decimal digits (i. e. ‘0’ to ‘9’). the first digit entered will be set as the most significant nibble of al and the second digit entered will be set as the least significant nibble of al. process appropriately the two characters and store in al the value meant by the user. example: suppose the user enters the digit ‘9’ followed by the digit ‘4’. this means that the user means the byte 94h. your program must ultimately store in al the value 94h = (1001 0100)2. the digit ‘9’ ‘produced the most significant nibble (1001)2 and the digit ‘4’ ‘produced the least significant nibble (0100)