Introductory Elements: Dependability Issues -- Destructive Mechanisms -- General Context -- Failures and Faults -- Faults and their Effects -- Fault and Error Models -- Protective Mechanisms -- Towards the Mastering of Faults and their Effects -- Dependability Assessment -- Redundancy -- Fault Avoidance Means -- Avoidance of Functional Faults During Specification -- Avoidance of Functional Faults During Design -- Prevention of Technological Faults -- Removal of Technological Faults -- Structural Testing Methods -- Design For Testability -- Fault Tolerance Means -- Error Detecting and Correcting Codes -- On-Line Testing -- Fail-Safe Systems -- Fault-Tolerant Systems -- Conclusions. Error Detecting and Correcting Codes -- Reliability Block Diagrams -- Testing Features of a Microprocessor -- Study of a Software Product.