| Systems with or without memory: |
| A system is said to be memoryless if the output for each value of the independent variable at a given time n depends only on the input value at time n. For example system specified by the relationship
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| is memoryless. A particularly simple memoryless system is the identity system defined by
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| In general we can write input-output relationship for memoryless system as
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| Not all systems are memoryless. A simple example of system with memory is a delay defined by
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| A system with memory retains or stores information about input values at times other than the current input value. |
