C-09

Lecture 9Lecture 9Version 1.0Version 1.0

Introduction to FunctionsIntroduction to Functions

Call by ValueCall by Value

2Rushdi Shams, Dept of CSE, KUET, Bangladesh

Introduction to Introduction to FunctionsFunctions

We have already known that in a C We have already known that in a C program, there must be a main () function program, there must be a main () function

In C, we used many library functions as In C, we used many library functions as well- printf (), scanf (), clrscr (), or getch well- printf (), scanf (), clrscr (), or getch () ()

printf() prints on the output printf() prints on the output scanf () takes input from the user and scanf () takes input from the user and

assigns that input to a variable by going assigns that input to a variable by going to the variable’s address to the variable’s address



clrscr () clears the output buffer clrscr () clears the output buffer getch () waits for a key-stroke from getch () waits for a key-stroke from

the user the user if you think uniform one thing is if you think uniform one thing is

common to say- the function does common to say- the function does one particular job. Isn’t it? one particular job. Isn’t it?



In C, user can define functions as In C, user can define functions as well- as many functions as they wish. well- as many functions as they wish. These functions are called user These functions are called user defined functionsdefined functions


Example of FunctionExample of Function


Another ExampleAnother Example


What We have learnt?What We have learnt?

There is no limit on the number of There is no limit on the number of functions that might be present in a functions that might be present in a C program. C program.

Each function in a program is called Each function in a program is called in the sequence specified by the in the sequence specified by the function calls.function calls.

After each function has done its job, After each function has done its job, control returns to the place of control returns to the place of calling that function.calling that function.


Well, then, should all the function Well, then, should all the function calls take place inside the main () calls take place inside the main () function? No! Functions defined by function? No! Functions defined by the user can call other functions as the user can call other functions as well. well.


We have known a lot!!We have known a lot!!

C program is a collection of one or more C program is a collection of one or more functions. functions.

A function gets called when the function A function gets called when the function name is followed by a semicolon. name is followed by a semicolon.



A function is defined when function A function is defined when function name is followed by a pair of braces in name is followed by a pair of braces in which one or more statements may be which one or more statements may be present. present.



Any function can be called from any Any function can be called from any other function. Even other function. Even main( ) main( ) can be can be called from other functions. called from other functions.



A function can be called any number of A function can be called any number of times. times.



The order in which the functions are The order in which the functions are defined in a program and the order in defined in a program and the order in which they get called need not which they get called need not necessarily be same necessarily be same


We have known a lot!!We have known a lot!! A function can be called from other A function can be called from other

function, but a function cannot be defined in function, but a function cannot be defined in another function. Thus, the following another function. Thus, the following program code would be wrong, since program code would be wrong, since argentina( ) argentina( ) is being defined inside is being defined inside another function, another function, main( )main( )..



There are basically two types of There are basically two types of functions: functions:

Library functions Ex. Library functions Ex. printf( )printf( ), , scanf( ) scanf( ) etc. etc.

User-defined functions Ex. User-defined functions Ex. argentina( )argentina( ), , brazil( ) brazil( ) etc. etc.



Function Declaration or function Function Declaration or function prototypingprototyping

Function Definition or function bodyFunction Definition or function body The basic format of function definition is- The basic format of function definition is-



We have seen only void as the return-type We have seen only void as the return-type in functions so far. But it can be of any valid in functions so far. But it can be of any valid C data type. It specifies what type of data C data type. It specifies what type of data the function will hand over to the caller the function will hand over to the caller

Parameter-list is a comma separated list Parameter-list is a comma separated list containing declaration of parameters containing declaration of parameters received by the function when it is called. received by the function when it is called. We have also seen only void in the We have also seen only void in the parameter-lists so far (it means the function parameter-lists so far (it means the function does not get any value from the caller) does not get any value from the caller)



10,20,30

maximum(10,20,30)

maximum(10,20,30)

C-09

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