How are applications and data accessed by the CPU from RAM

Question

I am having a bit of trouble understanding how applications and data are accessed by the CPU from RAM after the application has been loaded into RAM and a file opened (thus data

Answer 1

CPU,as you've noticed, reads the program from RAM, instruction by instruction. When an instruction is executed, it might refer to data stored in memory, which it either fetches explicitly to the registers (internal storage of the CPU, quite small - on x86_64 that's like several 64-bit registers + other stuff like segment registers, IP, SP etc) with a separate instruction, or the data read from the memory (we are talking about small amount of data). That's all it really does.

Loading a file from a disk would be done by asking the appropriate controller to fetch the data into a specific place in memory. CPU is connected to buses which will carry instructions to appropriate controllers.

As to interrupts these are special things - CPU has several interrupt lines which can be activated by various devices, for example your network card. When it receives such an interrupt, it is usually handled by an interrupt handler, which is just a program located in a well-known place in memory. They can be registered by, for example, operating system. Each interrupt line has its own interrupt handler. When interrupt happens, the CPU saves the current state of the program it happens to be executing, handles interrupt, restores the state and resumes the program.