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Systems, methods and computer program products for providing a nested two-bit symbol bus error correcting code. Methods include constructing a nested error correcting code (ECC) scheme. The method includes receiving a Hamming distance n code. A symbol correcting code H-matrix is created by iterative

Systems, methods and computer program products for providing a nested two-bit symbol bus error correcting code. Methods include constructing a nested error correcting code (ECC) scheme. The method includes receiving a Hamming distance n code. A symbol correcting code H-matrix is created by iteratively adding rows of H-matrix bits on a symbol column basis such that the symbol correcting code H-matrix describes a symbol correcting code, and the Hamming distance n code is preserved as a subset of the symbol correcting code H-matrix.

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The invention claimed is: 1. A computer implemented method of constructing a nested error correcting code (ECC) scheme, the method comprising: receiving in a computer system a Hamming distance n code; and creating in the computer system a symbol correcting code H-matrix by iteratively adding rows o

The invention claimed is: 1. A computer implemented method of constructing a nested error correcting code (ECC) scheme, the method comprising: receiving in a computer system a Hamming distance n code; and creating in the computer system a symbol correcting code H-matrix by iteratively adding rows of H-matrix bits on a symbol column basis such that the symbol correcting code H-matrix describes a symbol correcting code, and the Hamming distance n code is preserved as a subset of the symbol correcting code H-matrix. 2. The method of claim 1 wherein the Hamming distance n code is a single error correcting and double error detecting (SEC/DED) code. 3. The method of claim 1 wherein the symbol correcting code is a single two-bit symbol error correcting and double two-bit symbol error detecting (S2EC/D2ED) code. 4. The method of claim 1 wherein the creating includes verifying the symbol correcting code H-matrix using a MacWilliams identity. 5. The method of claim 1 wherein the creating includes verifying the symbol correcting code H-matrix using an exhaustive trial and error method. 6. The method of claim 1 wherein the Hamming distance n code is utilized for detecting and correcting memory errors. 7. The method of claim 1 wherein the symbol correcting code is utilized for detecting and correcting bus errors. 8. A computer program product for constructing a nested ECC scheme, the computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for facilitating a method, the method including: receiving a Hamming distance n code; and creating a symbol correcting code H-matrix by iteratively adding rows of H-matrix bits on a symbol column basis such that the symbol correcting code H-matrix describes a symbol correcting code, and the Hamming distance n code is preserved as a subset of the symbol correcting code H-matrix. 9. The computer program product of claim 8 wherein the Hamming distance n code is a SEC/DED code. 10. The computer program product of claim 8 wherein the symbol correcting code is a two-bit symbol error correcting code. 11. The computer program product of claim 8 wherein the symbol correcting code is a S2EC/D2ED code. 12. The computer program product of claim 8 wherein the symbol correcting code is a double two-bit symbol error detecting code. 13. The computer program product of claim 8 wherein the Hamming distance n code is formatted as a H-matrix that is a subset of the symbol correcting code H-matrix and the creating includes adding additional rows and columns to the Hamming distance n code H-matrix. 14. The computer program product of claim 8 wherein the creating verifying the symbol correcting code H-matrix using one or more of a MacWilliams identity and an exhaustive trial and error method. 15. A computer or communications or storage system with a nested ECC scheme, the system comprising: a first code to provide error correcting capabilities, the first code including first code checkbits and first code databits; a second, different code to provide different error correcting capabilities, the second code including additional second code checkbits, said second code having said first code as a subset of said second code; and a circuit capable of sending the first code and the second code checkbits over a bus in two or more transfers, wherein the first code checkbits and the second code checkbits are both always applied to the first code databits; and the circuit also capable of performing a method comprising receiving a Hamming distance n code and creating a symbol correcting code H-matrix by iteratively adding rows of H-matrix bits on a symbol column basis such that the symbol correcting code H-matrix describes a symbol correcting code, and the Hamming distance n code is preserved as a subset of the symbol correcting code H-matrix, wherein the Hamming distance n code is the first code and the symbol correcting code H-matrix is the second code. 16. The system of claim 15, wherein the Hamming distance n code is a SEC/DED code. 17. The system of claim 15, wherein the symbol correcting code is a S2EC/D2ED code. 18. The system of claim 15, wherein the Hamming distance n code is formatted as a H-matrix that is a subset of the symbol correcting code H-matrix and the creating includes adding additional rows and columns to the Hamming distance n code H-matrix. 19. The system of claim 15, wherein the Hamming distance n code is the first code, and the symbol correcting code is the second code.