## 3 Results
### Influence Analysis between Embedded Software Defects  
The DEMATEL method determined the degree of a defect's influence power as each defect related to each other, enabling this study to plot an IRM, as shown in Figure 3. The D column lists are the sum of rows, and the R column lists are the sum of columns. The D value numerically expresses the degree to which one defect affects other defects, while the R-value expresses the degree to which one defect is affected by other defects. D+R is the sum of the values affecting other defects and the  
defects and belong to the effect defect group [25]. Additionally, the affecting defect, or the cause defect, should be tested first because it affects other defects. Meanwhile, the affected defect should be tested later as it is affected by other defects [30]. Therefore, defects with higher D-R values should be tested first, whereas defects with lower D-R values should be tested later. As shown in Table 13, the D-R values of the following defects are positive and should be tested first: wrong logic (E9), wrong function (E10), flash memory and file system defects (E6), data and shared memory (E4), dynamic memory (E5), internal software interface (E7), and exception handling (E12). Meanwhile, the D-R values of the following defects are negative and should be tested later: task management (E11), device driver (E1), hardware interrupt (E2), timing error (E3), and the external interface (E8) defects. As defined at the beginning of the paper, core defects refer to defects that increasingly get more severe due to other defects. Based on this, the five core defects that have been identified in the effect group with negative D-R values and different characteristics are the following: external interface (E6), timing error (E9), hardware interrupt (E8), device driver (E7), and task management (E3). Minimizing these defects is vital, so tests that are appropriate for each defect characteristic should be performed. The characteristics of the five core defects that were derived are as follows: the primary core defects are defects with the smallest D-R value, which is an external interface fault, including network, serial port, and human interface. For example, if there are defects in the human interface, other functions can still work in a particular way and cause problems even if the user requests for the desired function. It can be understood as the most important fault as it can lead to serious problems due to incorrect operation if commands from an external system are incorrectly received. The second important defect is the hardware interrupt defect, which includes operations like dividing by zero, overflow, underflow, etc. If defects that interrupt processing occur, serious problems may follow. The third important defect is the device driver, providing the interface to control the hardware. Defects occurring in the device driver are essential to note because they prevent users from predicting how the embedded system will  
Figure 3: The impact relationship map of embedded software defects. operate. The fourth important defect is the timing error. Embedded systems can be directly linked to human life, such as automobile autonomous navigation systems, automatic navigation systems in aviation, nuclear power plant control systems, and missile control devices in the defense industry. If an immediate response function times out, unpredictable consequences may occur. The last important defect is the task management defect since tasks may not be performed normally due to deadlock, race condition, etc. In a comprehensive interpretation of core defects, this study found that embedded systems should be executed robustly without being affected by external systems and environments, and that interrupt should be handled correctly. They should then be implemented to respond to different types of hardware. The desired function must be performed within a limited time, ensuring that the original function is executed faithfully without damaging other task types.