CSAPP_1_计算机系统漫游

Posted on Jun 3, 2022

The goal got this book is to help you underestand what happens and why when you run programmer on a system.

Preprocessing phase: modifies the original C program, list exchange include code.
Compilation phase: translate text file to assembly-language program. Assembly-language is useful because it provides a common output language for different compilers for different high-level languages.
Assembly phase: translate assemly-language to machine-language instruction, packages them in a from known as a relocatable object program, and store in the object file hello.o
Linking phase: hello program use standard C library(printf.o). The linker merge hello.o and printf.o and create the hello file, which is an executable object file.

Optimizing program performance: in order to make good coding decisions in programs, we do need a basic understanding of machine-level code and how the compiler translates different C statements into machine code. [chapter 3, 6]
Understanding link-time errors: For example: what does it mean when the linker reports hat it cannot resolve a reference? What id the difference between a static library and a dynamic library? [chapter 7]
Avoiding security holes: Too few programmers understand the need to carefully restrict the quantity and forms of data they accept from untrustes sources. [chapter 3]

Buses: Running throughout the system is a collection of electrical conduits called buses that carry bytes of information back and forth between the components.
I/O devices: I/O devices are the system`s connection to the external world. For example keyboard, mouse and disk drive.
Main memory: The main memory is a temporary storage device that holds both a program and the data it manipulates while processor is excuting the program.
Processor: The central processing uint(CPU), or simply processor, is the engine that interprets (or executes) instructions stored in main memory.

⭐️application programmers who are aware of cache memories can exploit them to improve the performance of their programs by an order of magnitude.

to protect the hardware from misuse by runaway applications.
to provide applications with simple and uniform mechanisms for manipulating complicated and often wildly different low-level hardware devices.

Processes: A process is the operating system’s abstraction for a running program.
Threads: Although we normally think of a process as having a single control flow, in modern systems a process can actually consist of multiple execution units, called threads, each running in the context of the process and sharing the same code and global data.
Files: A file is a sequence of bytes, nothing more and nothing less. Every I/O device, including disks, keyboards, displays, and even networks, is modeled as a file. All input and output in the system is performed by reading and writing files, using a small set of system calls known as Unix I/O.
Virtual Memory: Virtual memory is an abstraction that provides each process with the illusion that it has exclusive use of the main memory.

Processes Concurrency: All programs can be processed simultaneously by switching between threads or processes on one CPU core.
Processes Parallelism: Multiple CPU cores executing different processes or threads at the same time
Instruction-Level Parallelism: At a much lower level of abstraction, modern processors can execute multiple instructions at one time.
Single-Instruction, Multiple-Data (SIMD) Parallelism: At the lowest level, many modern processors have special hardware that allows a single instruction to cause multiple operations to be performed in parallel.