Draw a logic diagram by identifying the inputs, arranging the gates in the order in which operations occur, and connecting each gate’s output to the next required input. Label the final output and any intermediate signals clearly.
Method
A logic diagram shows how logic gates process binary inputs to produce an output. When given a Boolean expression, work from the highest-priority operation outward: NOT first, then AND, then OR, unless brackets specify a different order.
| Step | Action |
|---|---|
| 1 | Write the input variables on the left, such as , , and . |
| 2 | Identify each operation: NOT, AND, OR, XOR, NAND, or NOR. |
| 3 | Draw gates from left to right in processing order. |
| 4 | Connect outputs to the inputs of later gates. |
| 5 | Label intermediate outputs and the final output. |
For example, consider the expression:
First, connect and to an AND gate. Label its output , where . Next, connect to a NOT gate and label its output , where . Finally, connect and to an OR gate; its output is .
The signal paths can be summarized before drawing standard gate symbols:
| Path | Result |
|---|---|
| and | AND produces |
| NOT produces | |
| and |
A common misconception is that gates should be drawn in the order their names appear when reading the expression casually. Instead, follow brackets and operator precedence. Wires that cross are not connected unless a junction is explicitly marked; wires meeting at a marked junction are connected.
To verify the diagram, trace one input combination through every gate and compare the final result with its truth-table row.
Exam Technique
Under IB Computer Science topic A1.2, use standard gate symbols, label inputs and outputs, and make connections unambiguous. Check the diagram against a truth table.
