A significant part of an embedded developer's work is dealing with hardware. Unlike most application developers, embedded developers cannot rely on hardware. Hardware fails for different reasons and embedded developers have to distinguish purely software failures from software failures caused by hardware failures or glitches.
Embedded systems are based on specialized hardware designed and manufactured for a particular use case. This implies that at the time that the software for the embedded system is being developed, its hardware is not yet stable and well tested. When software developers encounter an error in their code behavior, it does not necessarily mean there is a software bug but it might be a result of incorrectly working hardware.
It is hard to triage these kinds of problems. They require knowledge, intuition, and sometimes the use of an oscilloscope to narrow the root cause of an issue down to hardware.
Hardware is inherently unreliable. Each hardware component has a probability of failure and developers should be aware that hardware can fail at any time. Data stored in memory can be corrupted because of memory failure. Messages being transmitted over a communication channel can be altered because of external noise.
Embedded developers are prepared for these situations. They use checksums or cyclic redundancy check (CRC) code to detect and, if possible, correct corrupted data.
High temperature, low temperature, high humidity, vibration, dust, and other environmental factors can significantly affect the performance and reliability of hardware. While developers design their software to handle all potential hardware errors, it is common practice to test the system in different environments. Besides that, knowledge of environmental conditions can give an important clue when working on the root-cause analysis of an issue.