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A non-prefix-free code causes ambiguity because a received bit string can be segmented in more than one way into valid codewords. For Code 3, the received string 00 can be parsed as two copies of the codeword 0 (giving $x_1x_1$) or as one copy of the codeword 00 (giving $x_3$).

Conditions: Occurs when at least one codeword is a prefix of another codeword.; Illustrated here for concatenated received strings under Code 3.

A non-prefix-free code causes ambiguity because a received bit string can be segmented in more than one way into valid codewords. For Code 3, the received string 00 can be parsed as two copies of the codeword 0 (giving $x_1x_1$) or as one copy of the codeword 00 (giving $x_3$).

Conditions: Occurs when at least one codeword is a prefix of another codeword.; Illustrated here for concatenated received strings under Code 3.

Code 3 fails the prefix-free condition because specific codewords act as prefixes for other codewords within the same code. Specifically, the codeword 0 assigned to $x_1$ is a prefix of the codeword 00 assigned to $x_3$, and the codeword 1 assigned to $x_2$ is a prefix of the codeword 11 assigned to $x_4$.

Conditions: Use the Code 3 column of the displayed table.; Apply the prefix-free definition: no codeword is a prefix of another.

Code 3 fails the prefix-free condition because specific codewords act as prefixes for other codewords within the same code. Specifically, the codeword 0 assigned to $x_1$ is a prefix of the codeword 00 assigned to $x_3$, and the codeword 1 assigned to $x_2$ is a prefix of the codeword 11 assigned to $x_4$.

Conditions: Use the Code 3 column of the displayed table.; Apply the prefix-free definition: no codeword is a prefix of another.