1. How many input rows has a truth table with 3 Boolean inputs?
- 8
- 3
- 6
Check the answer and reasoning
8
Each input has two states, giving 2³ combinations.
CS / AS level
Processor architecture and logic circuits
Registers, buses and instruction formats support stored-program execution. Addressing modes specify how operand locations or values are obtained.
Learning objectives
- Explain processor architecture and logic circuits using a concrete example.
- Apply the worked method and justify each step.
- Recognise the limitation described in the final check.
The big idea
Registers, buses and instruction formats support stored-program execution. Addressing modes specify how operand locations or values are obtained.
Combinational circuits derive outputs from current inputs; sequential circuits also retain state. Boolean algebra can simplify circuits while preserving their truth tables.
Worked example
In immediate addressing, where is the operand value found?
Follow the solution
The instruction directly contains the value rather than an address to fetch it from.
Investigate and explain
Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.
Use the prediction activity below; a local model appears only where it supports this topic.
Check your understanding
2. In immediate addressing, where is the operand value found?
- Always in the next disk sector
- In the instruction
- Only in a network packet
Check the answer and reasoning
In the instruction
The instruction directly contains the value rather than an address to fetch it from.
3. Does a simpler equivalent expression need the same truth table?
- No
- Only for AND gates
- Yes
Check the answer and reasoning
Yes
Equivalence requires identical outputs for every permitted input combination.