C语言基础教程课件(英文版)ch03.pptVIP

* * * * * * * * * * * * * * * * * * * * * A First Book of ANSI C, Fourth Edition * Summary (continued) It is good programming practice to display a message, prior to a scanf() function call, that alerts the user as to the type and number of data items to be entered Field width specifiers can be included with conversion control sequences to explicitly specify the format of displayed fields Each compiled C program is automatically passed through a preprocessor Expressions can be made equivalent to a single identifier using the preprocessor #define command A First Book of ANSI C, Fourth Edition * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * A First Book of ANSI C, Fourth Edition * Mathematical Library Functions (continued) A First Book of ANSI C, Fourth Edition * Interactive Input A First Book of ANSI C, Fourth Edition * Interactive Input (continued) This program must be rewritten to multiply different numbers scanf() is used to enter data into a program while it is executing; the value is stored in a variable It requires a control string as the first argument inside the function name parentheses A First Book of ANSI C, Fourth Edition * Interactive Input (continued) The control string passed to scanf() typically consists of conversion control sequences only scanf() requires that a list of variable addresses follow the control string scanf(%d, num1); A First Book of ANSI C, Fourth Edition * Interactive Input (continued) A First Book of ANSI C, Fourth Edition * Interactive Input (continued) This statement produces a prompt Address operator () A First Book of ANSI C, Fourth Edition * Interactive Input (continued) scanf() can be used to enter many values scanf(%f %f,num1,num2); //%f%f is the same A space can affect what the value being entered is when scanf() is expecting a character data type scanf(%c%c%c,ch1,ch2,ch3); stores the next three characters typed in the variables ch1, ch2, and ch3; if you type x y z, then x is stored in ch1, a blank is stored in