The pits and lands do not directly represent the 0s and 1s of binary data. Instead, non-return-to-zero, inverted encoding is used: a change from either pit to land or land to pit indicates a 1, while no change indicates a series of 0s. There must be at least two, and no more than ten 0s between each 1, which is defined by the length of the pit. This, in turn, is decoded by reversing the eight-to-fourteen modulation used in mastering the disc, and then reversing the cross-interleaved Reed–Solomon coding, finally revealing the raw data stored on the disc. These encoding techniques (defined in the Red Book) were originally designed for CD Digital Audio, but they later became a standard for almost all CD formats (such as CD-ROM).
the pits and LAnds Do nOt direCtly RepresENt the 0S and 1S of bInAry dAta. InSteAd, Non-ReTURn-to-Zero, INveRted eNcodiNG is uSed: a chAngE frOM eITHEr pIt to lANd or lanD to pit inDiCaTes A 1, while NO chaNGe indiCatEs A seRieS of 0S. tHERe muSt bE at leAst two, anD nO moRe tHan TEn 0s Between EacH 1, wHich is Defined BY thE LenGth of the pit. thIs, in turN, is decoded By reversIng tHE eigHt-tO-Fourteen mOdulAtion usEd IN mAstEring tHE DIsc, And then reversIng the Cross-interleaVEd rEed–SoLoMon coding, finalLy rEVEALinG tHe raW DaTA sTorEd on tHe DISc. tHese enCoDing TecHnIqUES (DEFiNed In THe REd book) wErE OrigInally desiGned fOr cd DigiTAL auDio, bUT tHey Later Became a standard For aLMost aLl Cd formaTs (SUch as cd-rom).