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Introduction to Computer Science

Summary

Introduction to Computer ScienceSummary

Summary

4.1 Models of Computation

  • A computational model defines what an algorithm or program does. There are hardware models, programming language models, and abstract models.
  • Low-level programming means writing machine code that can be understood by a CPU directly, or something very near to that. It is laborious but yields very fast code.
  • Middle-level programming is a compromise that is reasonably efficient and more convenient than low-level programming.
  • High-level programming is more abstract and intuitive for humans. It is less labor-intensive, but high-level code can be slower than low-level code.
  • Programming language paradigms are approaches for organizing source code.
  • In the imperative paradigm, code orders the CPU to execute specific actions.
  • In the declarative paradigm, the programmer declares the outcome that they need.
  • In the functional paradigm, the programmer defines mathematical functions to evaluate.
  • In structured programming, the flow of execution is specified with explicit syntax elements (“if-then-else,” “for” loop, “while” loop) and never GOTO.
  • In procedural programming, a program is divided into procedures. Each procedure performs one specific task and has a descriptive name.
  • In object-oriented programming, the basic building block is an object. An object combines data and procedures that together represent a human concept.

4.2 Building C Programs

  • The C programming language is the most prominent example of a low-level language. Programs written in C typically execute as fast as assembly language and allow programmers to directly manipulate machine features such as memory via the use of pointers.
  • The C programming language is used by most of the system software we depend on today (e.g., operating systems, compilers, interpreters, and device drivers) because of its efficient execution, portability, and modularity.
  • The C data model supports the creation of a variety of basic types including integers and floating point numbers, as well as pointers. C also provides type constructors used to create collections using the array, struct, and union keywords.
  • C supports the imperative and structured/procedural programming paradigms and allows for conditional and iterative statements as well as functions, which can leverage recursion.
  • Program development steps in C require designing algorithms, developing programs that implement algorithms, and compiling, linking, and executing programs. All of these steps may be performed within a C development environment, which is a suite of tools that a programmer uses to create software. It must include a text editor, compiler, and linker, and may include other tools such as a version control manager, and others.
  • A development environment may be an assemblage of separate command-line programs, or an IDE, which is a development environment bundled into a single app. There are a multitude of C development environments, and many of them are free to use.
  • Compiling C programs involves converting C into assembly language, which can itself be translated into machine code. This process is performed by using a combination tools known respectively as a C compiler, assembler, and linker. The GCC compiler is an open-source C compiler developed by the GNU project, it include gcc, ar, and ld to implement compiling, assembly, and linking.
  • Linking is the process of combining the .o files that result from separate C modules into one deliverable library or executable program.
  • A library is a file that contains the object code of compiled functions. There are several variations of libraries (static, dynamic, shared) and ways of linking them (load-time, run-time).
  • Version control tools manage the files created in programming, facilitating collaboration, backups, and undoing errors.

4.3 Parallel Programming Models

  • Multicore computers are commonplace. Most consumer mobile devices, computers, and video game consoles have between two and eight cores. As time goes on, the number of cores in computers tends to increase.
  • Parallel computing does not happen automatically. Rather, a programmer must deliberately write a program in a parallel manner in order for it to use multiple cores.
  • A variety of models of parallel programming exist, including shared memory, threads, and message passing.
  • OpenMP is a library for writing parallel code using the message-passing model.
  • One strategy for parallel computing is to have a parent thread, which creates and controls child threads. The child threads work in parallel.

4.4 Applications of Programming Models

  • Low-level and middle-level programming will continue to be important as society increasingly relies on low-powered computing devices and IoT.
  • Middle-level languages including C are ideal for developing firmware and kernels.
  • Rust is a relatively new middle-level language that is gaining traction.
  • Arduino is an embedded computer platform. Arduino firmware can be written in C.
  • Raspberry Pi kernels can be developed in C.
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