4.1 Two communicating devices are using a single bit odd parity check for error detection. The transmitter sends the following 7 bits data: 1010101 1101101 1100111 1000001 1111111 Add parity-checking bit to each of the above data. [10] 4.2 Consider the following set of processes, with the length of the CPU burst given in milliseconds Process Burst time Priority A 2 1 B 1 2 C 3 2 D 2 1 The processes are assumed to have arrived in the order A, B, C, and D all at time 0. (i) Draw four Gantt charts that illustrate the execution of these processes using the following scheduling algorithms: Shortest Job First (SJF), First Come First Served (FCFS), Round Robin (RR), Modified Round Robin (MRR) which gives priority 1 processes a double quantum and

priority 2 processes a single quantum whenever they are scheduled. [5] (ii) Calculate the average turnaround time for each of these scheduling algorithms. [5] (iii) Calculate the average waiting time for each of these scheduling algorithms. [5]