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【正文】 olic constants and named constants A First Book of ANSI C, Fourth Edition 54 Symbolic Constants (continued) sign is a signal to a C preprocessor A First Book of ANSI C, Fourth Edition 55 Case Study: Interactive Input A First Book of ANSI C, Fourth Edition 56 Case Study: Interactive Input (continued) A First Book of ANSI C, Fourth Edition 57 Common Programming Errors ? Fetting to assign initial values to all variables before the variables are used in an expression ? Calling sqrt() with an integer argument ? Fetting to use the address operator, amp。, in front of variable names in a scanf() function call ? Not including the correct control sequences in scanf() function calls for the data values that must be entered ? Including a message within the control string passed to scanf() A First Book of ANSI C, Fourth Edition 58 Common Programming Errors (continued) ? Terminating a define mand to the preprocessor with a semicolon ? Placing an equal sign in a define mand when equating a symbolic constant to a value ? Using the increment and decrement operators with variables that appear more than once in the same expression ? Being unwilling to test a program in depth A First Book of ANSI C, Fourth Edition 59 Common Compiler Errors A First Book of ANSI C, Fourth Edition 60 Common Compiler Errors (continued) A First Book of ANSI C, Fourth Edition 61 Summary ? Arithmetic calculations can be performed using assignment statements or mathematical functions ? The assignment symbol, =, is an operator ? C provides the +=, =, *= and /= assignment operators ? The increment operator, ++, adds 1 to a variable ? The decrement operator, , subtracts 1 from a variable ? C provides library functions for calculating square root, logarithmic, and other mathematical putations A First Book of ANSI C, Fourth Edition 62 Summary (continued) ? Mathematical functions may be included within larger expressions ? scanf() is a standard library function used for data input ? When a scanf() function is encountered, the program temporarily suspends further statement execution until sufficient data has been entered for the number of variable addresses contained in the scanf() function call A First Book of ANSI C, Fourth Edition 63 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 piled C program is automatically passed through a preprocessor ? Expressions can be made equivalent to a single identifier using the preprocessor define mand A First Book of ANSI C, Fourth Edition 64
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