| 摘要 |
PURPOSE:To check the normality of a program by calculating a check sum again before executing the program and comparing the calculated value with that obtained at normal time. CONSTITUTION:A program to be executed in a CPU is written in an area A. On the other hand, the check sum of the program previously found out by calculation is written in an area B. In the case of executing the program, the CPU reads out the program from the area A and reads out the check sum from the area B. Before executing the program, the CPU calculates the check sum of the read program and compares the calculated check sum with that read out from the area B. When both the values coincide with each other as the compared result, the normality of the program is judged and the program is executed. When there is discrepancy between both the values, the existence of abnormality in the program is recognized. |
