Evaluating Expressions
Computer Science: OCR A Level, topic 4.3.4
Evaluating Expressions
Logic gates can be combined to form logic circuits that process complex logical statements such as A AND (B OR C).
Evaluating boolean expressions
- To evaluate a boolean expression, you should substitute all of the values in for the variables and then use the definitions of the different boolean functions to simplify it one step at a time.
Order of evaluation
- You should evaluate any expression in brackets first, for example:
- NOT(True OR False).
- NOT(True).
- False.
Truth tables
- Another method of evaluating an expression is using a truth table.
- A truth table shows every possible combination of inputs and the resulting output.
- The truth table shows the input and output state for each combination.
- The table can then be used to look up the output.
Test yourself on Evaluating Expressions
What is the value of True AND NOT(False)?
What is the value of NOT(False AND NOT(False))?