To write programs for Arm microcontrollers, you need to know both Assembly and C languages.
Since the ARM peripherals are not standard among the various ve.
However, the ARM licensees are free to implement the on-chip peripheral (ADC, Timers, I/O, etc.) as they choose.
The ARM Thumb-2 Assembly language is standard regardless of who makes the chip.
Now, most of the Arm Microcontrollers use the Thumb-2 instruction set.
The book covers Assembly language Programming for Cortex-M series Using Thumb-2.
To write programs for Arm microcontrollers, you need to know both Assembly and C languages