# Computer Systems a Programmer's Perspective  ## Metadata - Author: [[Randal E. Bryant, David R. O’Hallaron]] - Full Title: Computer Systems a Programmer's Perspective - Category: #books - Document Tags: [[computing]] [[Computing]] - Summary: The text explains the relationship between C, assembly code, and machine code, focusing on the x86-64 architecture. It covers how control structures, procedures, and data structures are implemented at the machine level, along with issues like out-of-bounds memory references. The chapter also discusses the role of registers and the use of the gdb debugger for analyzing machine-level programs. ## Highlights - A computer system consists of hardware and systems software that work to- gether to run application programs. ([View Highlight](https://read.readwise.io/read/01jttwbzp0vt6rg02q2b21agx0)) - You will learn the promises and pitfalls of concurrency, a topic of increasing importance as multiple processor cores are integrated onto single chips. ([View Highlight](https://read.readwise.io/read/01jttwjcbyebfkmhfthgrdb4fz)) - Our hello program begins life as a source program (or source file) that the programmer creates with an editor and saves in a text file called hello.c.The source program is a sequence of bits, each with a value of 0 or 1, organized in 8-bit chunks called bytes. Each byte represents some text character in the program. ([View Highlight](https://read.readwise.io/read/01jttwg94b2srcfvwg03pkc559)) - Most computer systems represent text characters using the ASCII standard that represents each character with a unique byte-size integer value ([View Highlight](https://read.readwise.io/read/01jttwgkjtsmaac2q0wjdmzzkx)) - The hello.c program is stored in a file as a sequence of bytes. Each byte has an integer value that corresponds to some character. ([View Highlight](https://read.readwise.io/read/01jv6a1hz8r5jbk1cy7jds4x6r)) - Files such as hello.c that consist exclusively of ASCII characters are known as text files. All other files are known as binary files. ([View Highlight](https://read.readwise.io/read/01jv6a1rzgcqnsd6k87xn43tkr)) - The only thing that distinguishes different data objects is the context in which we view them. For example, in different contexts, the same sequence of bytes might represent an integer, floating-point number, character string, or machine instruction. ([View Highlight](https://read.readwise.io/read/01jv6a2sjp3nfz6xm3enwj11mp)) - C was developed from 1969 to 1973 by Dennis Ritchie of Bell Laboratories. ([View Highlight](https://read.readwise.io/read/01jv6a3nsac2g88by237ajbtyb)) - C was closely tied with the Unix operating system. C was developed from the beginning as the system programming language for Unix. Most of the Unix kernel (the core part of the operating system), and all of its supporting tools and libraries, were written in C. As Unix became popular in universities in the late 1970s and early 1980s, many people were exposed to C and found that they liked it. Since Unix was written almost entirely in C, it could be easily ported to new machines, which created an even wider audience for both C and Unix. ([View Highlight](https://read.readwise.io/read/01jv6a5d63fry0gjrwwnkeaxmz)) - C pointers are a common source of confusion and programming errors. C also lacks explicit support for useful abstractions such as classes, objects, and exceptions. Newer languages such as C++ and Java address these issues for application-level programs. ([View Highlight](https://read.readwise.io/read/01jv6a6gsvtt6kzcnr0kxbagpw)) - The hello program begins life as a high-level C program because it can be read and understood by human beings in that form. However, in order to run hello.c on the system, the individual C statements must be translated by other programs into a sequence of low-level machine-language instructions. These instructions are then packaged in a form called an executable object program and stored as a binary disk file. Object programs are also referred to as executable object files. ([View Highlight](https://read.readwise.io/read/01jv8z7s2jhyvbdvrratjckz4j)) - The GNU project is a tax-exempt charity started by Richard Stallman in 1984, with the ambitious goal of developing a complete Unix-like system whose source code is unencumbered by restrictions on how it can be modified or distributed. The GNU project has developed an environment with all the major components of a Unix operating system, except for the kernel, which was developed separately by the Linux project. ([View Highlight](https://read.readwise.io/read/01jv8ynxhma97s9yfk0z32p60b))