ARM processor is a 32-bit reduced instruction set processor architecture, which is widely used in many embedded system designs. It contains the following three instruction types: ARM instruction, Thumb instruction and Thumb2 instruction, except that Thumb instruction is 16-bit, the other two are 32-bit.
One: the advantages of ARM processors
The advantage of ARM processors lies not in performance, but in execution efficiency. The ARM processor adopts the RISC pipeline instruction set, which is at a disadvantage in completing comprehensive work, and the advantages can be exerted in some applications where the task is relatively fixed.
In addition to high execution efficiency, ARM also has the advantages of fixed instruction length, low cost, low consumption, and small size.
The ARM-based computer connects the CPU to the data storage device through a dedicated data interface. Therefore, it is difficult to expand the storage and memory performance of the ARM processor (generally, the memory and data storage capacity has been determined during product design). The system adopting ARM structure generally does not consider expansion, and basically adheres to the principle of "enough is enough".
2: The relationship between native programs and arm assembly
The Android embedded intelligent operating system is based on the Linux kernel, and the embedded system Linux is based on the ARM platform.
Android native programs can execute programs. In the previous chapters, we learned how to write executable programs. During the writing process, configure the two .mk files so that the written program can run on the Android platform. It also depends on the ARM platform.
It can be seen that the native program runs based on the Linux kernel, and the processor is based on ARM.
summary:
I understand that the ARM processor has the advantages of high execution efficiency, low consumption, and embedded development. At the same time, I also know that the ARM processor can exert its greatest advantage when the task is relatively fixed. Finally, we also learned the relationship between Android and ARM: Android is based on the Linux kernel and uses the ARM processor.