The document discusses the differences between monolithic and modular programming, highlighting that modular programming is more advantageous due to easier debugging, reduced program size, and reusability of code. It also explains the concepts of functions in C, including prototypes, definitions, and the distinction between user-defined and standard functions. Furthermore, it covers function categories and demonstrates call by value and call by reference with code examples.

1. Programming in C
Function and Procedure
Ashis Talukder, PhD
Associate Professor
Department of MIS, DU
Dr. Ashis Talukder, Associate Professor, MIS, DU
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2. Monolithic vs modular programming
 Monolithic Programming indicates the program which contains a single
function for the large program.
 Modular programming help the programmer to divide the whole program
into different modules and each module is separately developed and
tested. Then the linker will link all these modules to form the complete
program.
 On the other hand monolithic programming will not divide the program
and it is a single thread of execution. When the program size increases it
leads inconvenience and difficult to maintain.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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3. Monolithic vs modular programming
 Disadvantages of monolithic programming:
 Difficult to check error on large programs.
 Difficult to maintain.
 Code can be specific to a particular problem. i.e. it can not be reused.
 Advantage of modular programming:
 Modular program are easier to code and debug.
 Reduces the programming size.
 Code can be reused in other programs.
 Problem can be isolated to specific module so easier to find the error and
correct it.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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4. Function
 A function is a group of statements that together
perform a task.
 Every C program has at least one function, which is
main(), and all the most trivial programs can define
additional functions.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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5. Function declaration of prototype
 It is also known as function prototype.
 Calling function need information about called function. If called function
is place before calling function then the declaration is not needed.
 It inform the computer about the three things
 Name of the function
 Number and type of arguments received by the function.
 Type of value return by the function
 Syntax :
return_type function_name (type1 arg1 , type2 arg2);
return_type function_name (type1 type2);
Dr. Ashis Talukder, Associate Professor, MIS, DU
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6. Function Definition
 It consists of code description and
code of a function.
 It consists of two parts
 a) Function header
 b) Function coding
 Function definition tells what are
the I/O function and what is going
to do.
Syntax:
return_type function_name (type1 arg1 , type2 arg2)
{
local variable;
statements ;
return (expression);
}
Dr. Ashis Talukder, Associate Professor, MIS, DU
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7. Function Definition
 Function definition can be placed any where in the program but
generally placed after the main function .
 Local variable declared inside the function is local to that function. It
cannot be used anywhere in the program and its existence is only
within the function.
 Function definition cannot be nested.
 Return type denote the type of value that function will return and return
type is optional if omitted it is assumed to be integer by default.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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8. User Defined Function Vs Standard
(built-in) Functions
 User Defined function
 A function that is declare, calling and define by the user is called user define function.
 Every user define function has three parts as:
 Prototype or Declaration
 Calling
 Definition
 Standard/Built-in Functions
 The C standard library is a standardized collection of header files and library routines
used to implement common operations, such as input/output and character string
handling.
 Unlike other languages (such as COBOL, FORTRAN, and PL/I) C does not include built
in keywords for these tasks, so nearly all C programs rely on the standard library to
function.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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9. Function Categories
 Function with no arguments and no return values.
 Function with no arguments and a return value.
 Function with arguments and no return values.
 Function with arguments and return values.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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10. Function Call
void swap (int a , int b) /* called function */
{
int t;
t = a;
a=b;
b = t;
}
void print (int a , int b) /* called function */
{
printf(“%d, %d”,a,b);
}
main( )
{
int k = 50,m= 25;
swap( k, m) ; / * calling function */
print (k, m); / * calling function */
}
Output:
50, 25
 Call by value
 Here value of actual arguments is
passed to the formal arguments and
operation is done in the formal
argument.
 Since formal arguments are photo
copy of actual argument, any change
of the formal arguments does not
affect the actual arguments
 Changes made to the formal
argument t are local to block of called
function, so when control back to
calling function changes made vanish.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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11. Function Call
void swap (int &a , int &b) /* called function */
{
int t;
t = a;
a=b;
b = t;
}
void print (int a , int b) /* called function */
{
printf(“%d, %d”,a,b);
}
main( )
{
int k = 50,m= 25;
swap( k, m) ; / * calling function */
print (k, m); / * calling function */
}
Output:
25, 50
 Call by Reference
 Here instead of passing value
address or reference are passed.
Function operators or address rather
than values.
 Here formal arguments are the
pointers to the actual arguments.
Dr. Ashis Talukder, Associate Professor, MIS, DU
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12. Examples
 Swap
 Factorial
 Prime
 Leap-year
 Reverse number
Dr. Ashis Talukder, Associate Professor, MIS, DU
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