Thursday, December 5, 2024

Functions

• In C, we can divide a large program into the basic Building Blocks known as Function

Unit-4 : Function and • The Function contains the set of programming statements enclosed by { }
• The Function is also known as Procedure or Sub-Routine in other programming

Dynamic Memory Allocation languages

• A Function is a complete and independent program which is used (or invoked) by the
main program or other subprograms

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Unit-4 : Function and Dynamic Memory Allocation Functions

• Functions: Designing structured programs, Declaring a function, • A function has Declaration:

• declaration
Signature of a function, Parameters and Return Type of a [ data type] function name (argument list);
• call
function, passing parameters to functions, call by value, Passing • definition
Call :

arrays to functions, passing pointers to functions, idea of call by [variable] = function name (value list);

reference, Some C standard functions and libraries. Definition:

• Recursion: Simple programs, such as Finding Factorial, Fibonacci [ data type] function name (argument list)
argument declaration
series etc., Limitations of Recursive functions {
local variable declarations;
• Dynamic memory allocation: Allocating and freeing memory, statements;
[return expression]
Allocating memory for arrays of different data types. }

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Ex: Basic Calculator application using Functions

2 1

3
Functions

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Advantages Function without argument and with return value

• It avoids rewriting same logic / code again and again in a program

• Can be called any number of times in a program and from any place in a program
• Reusability is the main achievement of Functions

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Function with Arguments and without return value

Different ways of calling a Function

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Without Arguments and Without Return Value Function with Arguments and with Return Value

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Q. WACP to find sum of elements of an array using a Function?

Arrays to Function

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Passing an Array to a Function Passing 2-D array to function

• Pass an array to a Function say fun(), it is always treated as a pointer by fun().

Pointer to array Length of array

It is compulsory
to pass length
Pointer takes
base address
of the array

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Ex: Passing Array to Function

Pointer to Function

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Passing a Pointer to a Function

• As an argument, a pointer is passed instead of a variable and its address is passed

instead of its value.
• As a result, any change made by the function using the pointer is permanently stored at
the address of the passed variable.
• In C, this is referred to as call by reference.

Recursion

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Ex: Passing a Pointer to a Function Recursion

• Generally, iterative solutions are more efficient than recursion since function call is always
overhead.
• Any problem that can be solved recursively, can also be solved iteratively.
• However, some problems are best suited to be solved by the recursion, for example, tower of
Hanoi, Fibonacci series, factorial finding, etc.

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Functions continued… Recursion

• Types of Function Call

• Call by Value
Call by Value :

[ variable] = function name (val1, val2 …);

• Call by Reference Call by Reference:

[variable] = function name (add1, add2, …);

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Recursion – First 50 Natural numbers using Recursion Recursion – Prime or NOT

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Flow Chart Recursion – Factorial of a number

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Recursion – SUM of numbers Recursion – Fibonacci series

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Recursion – Fibonacci series Some C standard Functions and Libraries

Function Library / Header File Description

printf() stdio.h To print on output console

scanf() stdio.h Used to take user input

int abs(int n) stdlib.h Absolute value of integer value n

void *malloc(size_t size) stdlib.h Reserves a block of storage

int getchar(void) stdio.h Reads a single character from std input

double log(double x) math.h Natural Logarithm of x

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Recursion – Fibonacci series Formatted Input Function – scanf()

• The function scanf() is used for formatted input from standard input and provides many
of the conversion facilities of the function

• Syntax
scanf (format, num1, num2,……);
• The function scnaf() reads and converts characters from the standards input depending
on the format specification string and stores the input in memory locations represented
by the other arguments (num1, num2,….)
• Ex:
scanf(“ %c %d”,&Name, &Roll No);

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Formatted Output Function

• Formatted Output - printf()

• formatted output to standard output based on a format specification.
• The format specification string, along with the data to be output, are the parameters to
the printf() function

• Syntax:
Other Standard Functions printf (format, data1, data2,……..);
In this syntax format is the format specification string. This string contains, for each
variable to be output, a specification beginning with the symbol % followed by a character
called the conversion character.

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Character Input Functions

• Character Input functions
• Character input functions is used to input a single character. All these functions are available in
'stdio.h' header file.
• getch(): Use to input single character at a time. But it will not display input character. get stands
for input, ch stands for character.
Syntax: char a = getch();

• getche(): It is same as getch() function but it will display input character. get stands for input, ch
stands for character, e stands for echo(display)
Syntax: char a = getche();
• Both getch() and getche() functions will not required enter key to terminate.

• getchar(): It will terminate by enter key after inputting a single character.

Syntax: char a = getchar();

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Character Output Functions

• Character output functions

• 1. putch(): use to print a single character.

• Syntax: putch(a);

• 2. putchar(): use to print a single character.

• Syntax: putchar(a);

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Binary Input Output Function

• A binary file is a file that uses all 8 bits of a byte for storing the information . The only
difference between the text file and binary file is the data contain in text file can be
recognized by the word processor while binary file data can't be recognized by a word
processor. ...

• In binary files, each byte may not be a character

NOTE : Formatted input/output(printf,scanf) ,

• character input/output(getchar, putchar),
• string input/output(fgets, fputs) functions can be used only with text files.

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