INSTRUCTION SET:
Processors are made of semiconductor dies, usually electronic-grade mono-crystalline silicon. They don't know English or any other human language, they understand only 0 and 1. So Until the designer of processor tells us in what sequence of zero's and one's we can instruct that specific processor. This numerical language of instructions is standardized as Machine Language andmanufacturer doesn't describe the set of machine instructions is called Instruction Set. A processor can act upon only specific type(s)technical specifications of instruction set.
Instruction sets can be 8/16/32/64-bit (defines how many instructions a processor can process at a time), last 2 being the common one these days.
WHAT IS SoC?
A System on Chip (SoC) is a small circuit that includes processors alongOS included with other components such as GPU, RAM, Flash/eMMC (equivalent of HDD or SSD), WiFi and bluetooth module, USB connectivity, UART (serial ports), JTAG (a very lower level serial communication protocol), GPSa device, modems (for cellular connectivity) and possibly others.
32-BIT VS. 64-BIT:
A processor can beit's hard to say if it's 32-bit or 64-bit. It depends on SoC manufacturers what they want to buildBut a device with their embedded system e.g. Snapdragon can be 32-bit or 64-bit. 32 hardware is expected to come with 64-bit ARM processors were improved for performance and new features were added from version 2OS (not always), let's take a look how to version 7.identify 64-bit support was introduced in ARMv8hardware.
To find out if a device is 32-bit or 64-bit, you need to check outthe specifications of its SoC (which you can see e.g. from https://gsmarena.com) and then of its processor. For instance if an SoC containsin Cotrex-53 processor such asRedmi Note 4 is Qualcomm Snapdragon 625 (MSM 8953), it'swhich contains processor Cortex-A53. It's evident from technical specifications of Cortex-53 that it's abased on ARMv8 architecture, which can process 2 types of Instruction Sets: aarch64 (which Android's arm64-v8a ABI uses) and aarch32 (which Android's armeabi-v7a ABI uses). So the phone is 64-bit ARMv8 processor having full backward compatibility, shipped with 32a 64-bit ARMv7OS.
On-device processor/SoC information can be checked using some third party app as you have mentioned, or directly from CLI: uname -m, cat /proc/cpuinfo, cat /sys/firmware/devicetree/base/model etc.
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