3rd-Learnings of the Week 3 [Caligdong]

false false false MicrosoftInternetExplorer4 we have discussed about the functions and structured programming of chapter 10.

• A c program is composed of at least one function definition, that is the main() function.
• Execution of the program begins with main() and also ends with the main() function.
• However, a C program can also be composed of other functions aside from the main().
• The c program presented in previous slide is composed of 3 functions: the main function, the function greet1 and the function greet2.
• Therefore we can say that we can create a program that is composed of other function aside from the main function.
• Note: The main( ) function should always be present in every C program.
• The c program presented in previous slide is composed of 3 functions: the main function, the function greet1 and the function greet2.
• Therefore we can say that we can create a program that is composed of other function aside from the main function.
• Note: The main( ) function should always be present in every C program.

FUNCTIONS

• Functions are the building blocks of C in which all program activity occurs.
• A function is also called a subprogram or subroutine. It is a part of a C program that performs a task, operation or computation then may return to the calling part of the program.
• Other functions aside from the main( ) can only be executed by the program through a “function call”.
• Note: Function call is a C statement that is used to call a function to execute C statements found inside the function body.
• Going back to the example, greet1( ); is an example of a function call, calling the function greet ( ).
• main ------clrscr------printf

greet1( ) function call------greet1( ) function greet2 function call----greet2( ) function getch( )

GENERAL FORM OF A FUNCTION

function_type function_name (parameters list)

{

body of the function;

}

Where

• function_type specifies the type of value that the function will return.
• function_name is any valid identifier name which will name the function.
• Parameter list is a comma separated list of variables that receive the values when the function is called.
• body of the function is composed of valid c statements that the function will execute.

ACTUAL PARAMETERS

• Actual Parameters are the variables found in the function call whose values will be passed to the formal parameters of the called function.
• Formal Parameters are the variables found in the function header that will receive from the actual parameters.

CALL BY VALUE AND PASS BY VALUE

• In the method call by value, the values of the actual parameters are passed to the formal parameters.

CALL BY VALUE

• In the method call by value, the values of the actual parameters are passed to the formal parameters.
• Changes that happen to the values of the formal parameters inside the function will not affect the values of the actual parameters.

PASS BY VALUE OR CALL BY REFERENCE

• The actual parameters also pass their value to the formal parameters.
• But the changes that happen to the values of the formal parameters inside the function will affect the values of the actual parameters.
• This is because the actual address of the variables is passed using the address of operator (&) together with the pointer operator (*).

#include

• sqrt(x)
• fabs(x) - calculates the absolute value of a number
• ceil(x) - ceil (11.25)=12
• floor(x) - floor(11.25)=11
• sin(x)
• cos(x)
• tan(x)
• pow(x,y)