C functions exchange information by means of parameters and arguments. The term parameter refers to any declaration within the parentheses following the function name in a function declaration or definition; the term argument refers to any expression within the parentheses of a function call. Show
The following rules apply to parameters and arguments of C functions:
5.6.1 Argument ConversionsIn a function call, the types of the evaluated arguments must match the types of their corresponding parameters. If they do not match, the following conversions are performed in a manner that depends on whether a prototype is in scope for the function:
No other default conversions are performed on arguments. If a particular argument must be converted to match the type of the corresponding parameter, use the cast operator. For more information about the cast operator, see Section 6.4.6. 5.6.2 Function and Array Identifiers as ArgumentsFunction and array identifiers can be specified as arguments to a function. Function identifiers are specified without parentheses, and array identifiers are specified without brackets. When so specified, the function or array identifier is evaluated as the address of that function or array. Also, the function must be declared or defined, even if its return value is an integer. Example 5-1 shows how and when to declare functions passed as arguments, and how to pass them. Example 5-1 Declaring Functions Passed as Argumentsint x() { return 25; } /* Function definition and */ int z[10]; /* array defined before use */ fn(int f1(), int (*f2)(), int a1[])) /* Function definition */ { f1(); /* Call to function f1 */ . . . } void caller(void) { int y(); /* Function declaration */ . . . fn(x, y, z); /* Function call: functions */ /* x and y, and array z */ /* passed as addresses */ . . . } int y(void) { return 30; } /* Function definition */ Key to Example 5-1:
5.6.3 Passing Arguments to the main Function The function called at program startup is named int main(void) { . . . } int main(int argc, char *argv[ ]) { . . . })argc The number of arguments in the command line that invoked the program. The value of argc is nonnegative. argv Pointer to an array of character strings that contain the arguments, one per string. The value argv[argc] is a null pointer. If the value of argc is greater than zero, the array members argv[0] through argv[argc - 1] inclusive contain pointers to strings, which are given implementation-defined values by the host environment before program startup. The intent is to supply the program with information determined before program startup from elsewhere in the host environment. If the host environment cannot supply strings with letters in both uppercase and lowercase, the host environment ensures that the strings are received in lowercase. If the value of argc is greater than zero, the string pointed to by argv[0] represents the program name; argv[0][0] is the null character if the program name is not available from the host environment. If the value of argc is greater than one, the strings pointed to by argv[1] through argv[argc - 1] represent the program parameters. The parameters argc and argv, and the strings pointed to by the argv array, can be modified by the program and keep their last-stored values between program startup and program termination. In the main function definition, parameters are optional. However, only the parameters that are defined can be accessed. See your platform-specific DEC C documentation for more information on the passing and return of arguments to the Previous Page | Next Page | Table of Contents | Index When only a copy of an argument is passed to a function it is said to be passed?Cards
When an argument is passed by value quizlet?When an argument is passed by value, the method has a copy of the argument, but does not have access to the original.
Is it possible for a function to have parameters with default arguments and some without?It is possible for a function to have some parameters with default arguments and some without. A function's return data type must be the same as the function's parameter(s). One reason for using functions is to break programs into manageable units, or modules. You must furnish an argument with a function call.
Which of the following must be included in the function header?Function definition
The header includes the name of the function and tells us (and the compiler) what type of data it expects to receive (the parameters) and the type of data it will return (return value type) to the calling function or program.
|