basic computer science questions

1. Answer the following questions very briefly:

a. Is CCA consider the following faults and show how the CCA will detect them:

i. A jump from the middle of a BFI to the beginning of another BFI

ii. A jump from end of a BFI to the middle of another valid predecessor BFI

iii. A jump from end of a BFI to the middle of another invalid predecessor BFI

b. Consider a linear array of processors used for matrix-vector multiplication.

Describe how weighted checksum can be used to correct single failures?

The linear array was of size 4 and the weights were 2, 1, 8, and 4,respectively. The checksum syndrome is –4 and the weighted checksum syndrome is –8. Determine the erroneous element.

c. Compare and contrast N-version program with Recovery Block Schemes

(RBS).

d. Describe (be brief) the DRB scheme for software fault tolerance. Discuss the various steps of operation for the following scenarios:

o Primary node fails

o Primary alternate on primary node fails

o Primary alternate on shadow node fails.

Consider these failures as disjoint events.

e. Explain reliability growth in software testing. Why is such growth not available in hardware testing?

2. Consider the Parity Check Matrix given

a. Write down the expressions for check elements assuming the first three

columns represent the check bits.

b. If the received code element is [000110] and only one error has been made

determine the erroneous bit and correct it.

c. What is the generator matrix?

3. What are the possible generator polynomials for 5 bit cyclic codes?

Generate all the codes for one of the generator polynomials.

4. Consider a single loop system consisting of 5 nodes v1, v2, ... v5. In this system node v1 tests v2, v2 tests v3 etc. and finally v5 tests v1.

i. What is the diagnosability of the system?

ii. Identify the fault patterns (more than one may exist) for thesyndrome 11001. The syndromes are written with the outcome of the test v1 ! v2 as the first element.