cout C

3 Key excerpts on "cout C"

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  eBook - ePub

  C Programming For Dummies

  • Dan Gookin(Author)
  • 2020(Publication Date)
  • For Dummies

    (Publisher)

  the basic function, of any computing device is input and output. The old I/O (say “eye oh”) is also the goal of just about every program. Input is received and processed, and then output is generated. The processing is what makes the program useful. Otherwise, you’d have only input and output, which is essentially the same thing as plumbing.

  Character I/O

  The simplest type of input and output takes place at the character level: One character goes in; one character comes out. Of course, getting to that point involves a wee bit of programming.

  Understanding input and output devices

  The C language was born with the Unix operating system. As such, it follows many of the rules for that operating system with regard to input and output. Those rules are pretty solid:

  • Input comes from the standard input device, stdin .
  • Output is sent to the standard output device, stdout .

  On a computer, the standard input device, stdin , is the keyboard. Input can also be redirected by the operating system, so it can come from another device, like a modem or a file.

  The standard output device, stdout , is the display. Output can be redirected so that it goes to another device, such as a printer or into a file.

  C language functions that deal with input and output access the stdin and stdout devices. They do not directly read from the keyboard or output to the screen. Well, unless you code your program to do so. (Such coding isn't covered in this book.)

  Bottom line: Although your programs can get input from the keyboard and send output to the display, you need to think about C language I/O in terms of stdin and stdout devices instead. If you forget that, you can get into trouble, which I happily demonstrate later in this chapter.

  Fetching characters with getchar()

  It's time for your code to become more interactive. Consider the source code from Listing 7-1 , which uses the getchar()

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  eBook - PDF

  Basic Data Structures and Program Statements

  • Xingni Zhou, Qiguang Miao, Lei Feng(Authors)
  • 2020(Publication Date)
  • De Gruyter

    (Publisher)

  4 Input/output Main content – Know the usage of basic input/output functions in C language. Learning objective – Can use basic input/output functions effectively. 4.1 Concept of input/output Mrs. Brown had a question when logging into a ticket purchasing website as shown in Figure 4.1. A program can read data from keyboard input, so the next question is, naturally, how does program exchange information with the real world? This is related to input/output of program data. The term input/output is used with respect to computer processors. Sending data from a computer to external output devices is called “ output, ” whereas send-ing data from input devices into computers is called “ input ” as shown in Figure 4.2. • When purchasing tickets online, Mrs. Brown was asked to type in password to log into the system. • Mrs. Brown asked curiously, “The password is entered through keyboard, how is it passed to the program?” • Mr. Brown commended, “Good question!” Case Study How does a program read password? How does a program read information from the real world, and send the processing result back? Figure 4.1: Login password problem. Input send data to computers through input devices These term are used from the perspective of computers Output : send data from computers to external output devices Figure 4.2: Input/output in computers. https://doi.org/10.1515/9783110692327-004 4.1.1 Standard input/output We usually call keyboards and monitors standard input/output devices. Consequently, input/output through these devices are called standard input/output, respectively as shown in Figure 4.3. 4.1.2 Standard library functions of C Recall that functions are child programs that provide certain functionalities. Library functions are functions inside a program library. Frequently used standard library functions of C and related questions are shown in Figure 4.4. The C language system provides its users with function libraries so that programmers can use programs within it directly.

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  eBook - ePub

  Scientific Programming: C-language, Algorithms And Models In Science

  C-Language, Algorithms and Models in Science

  • Luciano Maria Barone, Enzo Marinari, Giovanni Organtini, Federico Ricci Tersenghi(Authors)
  • 2013(Publication Date)
  • WSPC

    (Publisher)

  native functions which operate as an interface between I/O services of the system. The same holds for producing output. A program may write on devices, such as a terminal or a file, by using output functions of the language which depend on the operating system services.

  The C language uses the scanf function to receive input from the keyboard and the fscanf function to receive input from a file. The output functions are printf to write to a terminal and fprintf to write to a file. These functions have a very complex syntax allowing one to use a variety of formats. In the remainder of this section, we illustrate just a part of the existing options and refer the reader to a C language manual for a complete overview [Kernighan and Ritchie (1988); Kelley and Pohl (1998)]. We anticipate that when using the scanf function a symbol of the C language is included whose meaning shall be clarified in Chapter 6. For now it suffices to follow the syntax of the command.

  Listing 3.4 Measurement unit conversion with I/O.

  Reconsider the Listing 3.1 adding the I/O statements: examine the printf statement on line 5 in Listing 3.4. Between the parentheses ( ) there is a string of characters which is delimited by double quotes on each side " · · ·". On line 5, the string is Value in degrees Fahrenheit =, and this string is printed on the output device (for instance the terminal). The aim is to be able to write informative messages that indicate what the program is computing, or what operations it is performing and similar information. On line 8 the syntax of the string included between the parentheses ( ) is slightly different: besides the message to be printed, it also includes a term %f. This term is called a format specifier as it serves to specify the format of the variable which follows the message. In this case the format specifier %f informs the compiler that the variable tc is of the double type, such that it can be correctly printed out onto the output. The printf function admits a variable number of arguments, separated from each other by a comma ,

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