Question

Draw a Gantt chart that shows the completion times for each process
using first-come, first-served CPU scheduling with service times of 120, 60, 180, 50, and 300

Answer 1

To create a Gantt chart using the first-come, first-served (FCFS) scheduling method for processes with given service times of 120, 60, 180, 50, and 300, we first need to outline the processes and their corresponding completion times.

Let's denote the processes as:
- P1 = 120
- P2 = 60
- P3 = 180
- P4 = 50
- P5 = 300

### Step 1: Calculate Completion Times
Under FCFS, the processes are executed in the order they arrive. Assuming they arrive in the order listed above, we can calculate completion times as follows:

1. **Completion Time of P1:**
- Completion Time (CT) = 0 + 120 = 120
2. **Completion Time of P2:**
- CT = 120 + 60 = 180
3. **Completion Time of P3:**
- CT = 180 + 180 = 360
4. **Completion Time of P4:**
- CT = 360 + 50 = 410
5. **Completion Time of P5:**
- CT = 410 + 300 = 710

### Step 2: Gantt Chart Representation
Now we can represent this information in a Gantt chart.

```
| P1 | P2 | P3 | P4 | P5 |
0 120 180 360 410 710
```

### Explanation of the Gantt Chart:
- **P1** starts at 0 and finishes at 120.
- **P2** starts at 120 and finishes at 180.
- **P3** starts at 180 and finishes at 360.
- **P4** starts at 360 and finishes at 410.
- **P5** starts at 410 and finishes at 710.

The Gantt chart visually represents the order and duration of each process's execution using FCFS scheduling.