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FUNCTIONS(UNIT-IV)

Functions u2013 Definition u2013 Proto-types u2013 Passing arguments u2013 Recursions. Storage Class Automatic, External, Static, Register Variables, Passing arrays to functions.

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FUNCTIONS(UNIT-IV)

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  1. UNIT-IV FUNCTIONS Mr Sreenu Banoth Mr Sreenu Banoth Assistant Professor(CSE) Assistant Professor(CSE) IILM University IILM University

  2. SYLLABUS: Proto-types Automatic, Functions Recursions. Variables, Passing arrays to functions. Definition Storage Passing arguments Static, – – – – Class External, Register Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 2

  3. Function Definition: Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 3

  4. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 4

  5. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 5

  6. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 6

  7. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 7

  8. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 8

  9. Syntax: Data_type function_Name(List of parameters/Arguments); Example: int vaibhav(int a, int b….); { …… ……. return result; } 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 9

  10. PARAMETERS: • Parameters provides the data communication between the calling function and called function. • There are two types of parameters i)Actual parameter: -These are the parameters transferred from the calling program (main program) to the called program(function). ii)Formal parameter: -These are the parameters, used in the called program(function) to stand for the values that are passed from the called program (main program) Example: main() fun(x, y) { { ……. ……. ……. …… fun1(a, b); …... ……. …… ……. } } Where a,b are the Actual parameters. x,y are the Formal parameters. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 10

  11. FORMAL AND ACTUAL PARAMETERS/ARGUMENTS/VARIABLES • Arguments which are mentioned in the function CALL is as the actual arguments. • Arguments which are mentioned in the defilation of the function is called formal arguments. 23-11-2023 Computer Science and Engineering Mr Sreenu Banoth, Assistant Professor, Department of 11

  12. FUNCTION PROTYPES: The functions are classified into the following types depending on whether the arguments are present or not and whether the value is returned or not. These are also called function prototypes. A prototype statement keeps the compiler to check the return type and arguments types of the function. A function prototype declaration consists of the function’s return type, name and arguments.it is always terminated with semicolon. The following are the function prototype: i)Function without arguments and without return value. ii) Function with arguments and without return value. iii) Function without arguments and with return value. iv) Function with arguments and with return value. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 12

  13. i) Function without arguments and without return values. When a function has no arguments, it does not receive any data from the calling function. Similarly, when it does not return a value, the calling function does not receive any data from the called function. In effect, there is no data transfer between the calling function and called function. 1. Write a program to find a function without argument and without return values. #include<stdio.h> void add(); // function Declaration void main() { add(); //function call } //function definition void add() { int a=5,b=45; int c ; c= a+b; printf(“\n addition result:%d+%d=%d”,a,b,c); } When the above code is compiled and executed it produces the following result: Addition result:5+45=50 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering control No input function1(); { ………………. ………………. . Function2(); } Function2() { …………….. ……………. } No Output control 23-11-2023 13

  14. ii) Function with arguments and without return value. When a function has arguments, it does not receive any data from the calling function. Similarly, but it does not return a value, the calling function does not receive any data from the called function. In effect, there is data transfer between the calling function to called function. But not from the called function to the calling function.. 2. Write a program to find a function with argument and without return values #include<stdio.h> void sum(int ,int); // function Declaration void main() { int a,b; sum(a,b); //function call } //function definition void sum(int x, int y) { printf(“\n Enter the value of x,y:”); scanf(“%d%d”,&x, &y); printf(“\n sum of two numbers is x=%d\t y=%d\t sum=%d”, x, y, x+y); } When the above code is compiled and executed it produces the following result: Enter the value of x,y:6 7 Sum of two numbers is x=6 y=7 sum=13 Computer Science and Engineering control function1(); { int a,b; ………………. function2(a,b); } input a,b function2(int c, int d) { ………………. ………………. } No Output control The arguments in function2() of function1() are called as actual arguments i.e. a and b. The arguments in function2() are called as formal arguments i.e., c and d. 23-11-2023 • • Mr Sreenu Banoth, Assistant Professor, Department of 14

  15. iii) Function without arguments and with return value. When a function has no arguments, it does not receive any data from the calling function. Similarly, but it returns a value, the calling function receive any data from the called function. In effect, there is no data transfer between the calling function to the called function, but data transfer exists from called function to calling function. 3. Write a program to find a function without argument and with return values #include<stdio.h> int add2(); // function Declaration void main() { int c; c=add2(); //function call printf(“\n addition result:%d”, c); } //function definition int add2() { int a=10,b=20,c; c= a+b; return (c); } When the above code is compiled and executed it produces the following result: Addition result:10+20=30 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering control function2() { int sum, c,d; sum=c+d; return sum; } function1(); { ………………. ………………. function2(); } No input Output sum control 23-11-2023 15

  16. ii) Function with arguments and with return value. When a function has arguments, it receive any data from the calling function. Similarly, when it return a value, the calling function receive any data from the called function. In effect, there is data transfer between the calling function to called function and data transfer called function to calling function. 4. Write a program to find a function with argument and with return values #include<stdio.h> int add3(int a ,int b); // function Declaration void main() { int a=90,b=15, c; c=add3(a,b); //function call printf(“\n addition result:%d+%d=%d”, a ,b,c); } //function definition int add3(int a, int b) { int c; c=a+b; return c; } When the above code is compiled and executed it produces the following result: addition result:90+15=105 Computer Science and Engineering control function2(int c, int d) { int sum; sum=c+d; return sum; } input a,b function1(); { int a,b; function2(a,b); } Output sum control Mr Sreenu Banoth, Assistant Professor, Department of 23-11-2023 16

  17. NESTING OF FUNCTIONS: A function within a function is called as nesting of functions. 5. Example: #include<stdio.h> float checkno(float ); float div(float, float); main( ) { float a, b, res; printf(“Enter two numbers”); scanf(“%f%f”,&a,&b); div(a,b); } float div(float a, float b) { if(checkno(b)) printf(“Result = %f”, a/b); 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 17

  18. else printf(“Division not possible”); } float checkno(float b) { if(b!=0) return 1; else return 0; } Output: Enter two numbers25 32 Result = 0.781250 Enter two numbers50 35 Result = 1.428571 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 18

  19. Passing Parameters to the Function: There are two ways to pass the parameters:. 1. Call by value 2. Call by reference(Address) Call by Value: In call by value, original value can not be changed or modified. This method copies the actual values of an argument into the formal parameter of the function. Actual arguments are copied into formal arguments. Formal arguments cannot after actual arguments. Formal arguments are created after passing the actual arguments. Call by Reference: This method copies the address of an argument into the formal parameter. Inside the function, the address is used to access the actual argument used in the call. In this original values is changed or modified , because we pass reference(address) 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 19

  20. Difference Between Call by Value and Call by Reference CALL BY VALUE CALL BY REFERENCE 1. This method copies original value into 1. This method copy address of arguments function as a arguments. into function as a arguments. 2. Changes made to the parameter inside the 2.Changes made to the parameter effect the function have no effect on the argument. argument, because address is used to access the actual arguments. 3. Actual and formal arguments will be 3.Actual and formal arguments will be created in different memory location. created in same memory location. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 20

  21. 6. Write a program to find sum of two numbers using call by values and call by reference. a) Call by Values: #include<stdio.h> #include<conio.h> void swap(int a, int b); int main() { int a,b; printf("Enter the a,b"); scanf("%d%d", &a, &b); swap(a,b); } void swap(int p,int q) { int s; s=p+q; printf("s=%d",s); } 23-11-2023 Computer Science and Engineering Output: Enter the a,b 6 7 s=13 Mr Sreenu Banoth, Assistant Professor, Department of 21

  22. b) Call by reference: #include<stdio.h> #include<conio.h> void swap(int *a, int *b); int main() { int a,b; printf("Enter the a,b\n"); scanf("%d%d",&a,&b); swap(&a, &b); } void swap(int *p, int *q) { int c; c=*p+*q; printf(“c=%d", c); } Output: Enter the a,b 6 3 c=9 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 22

  23. 7. Write a program to swap two Numbers using call by value #include<stdio.h> void swap(int, int); void main() { int a,b; printf("Enter two numbers"); scanf("%d%d",&a,b); swap(a,b); printf("a=%d\n",a); printf("b=%d\n",b); getch(); } void swap(int x, int y) { int temp; temp=x; x=y; y=temp; } 23-11-2023 Output: Enter two numbers20 30 a=20 b=30 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23

  24. 8.Write a progrm to swap two Numbers using call by reference include<stdio.h> void swap(int *,int *); void main() { int a,b; printf("Enter two numbers"); scanf("%d%d",&a,&b); swap(&a,&b); printf("a=%d\n",a); printf("b=%d\n",b); getch(); } void swap(int *x,int *y) { int temp; temp=*x; *x=*y; *y=temp; } 23-11-2023 Output: Enter two numbers10 20 a=10 b=20 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 24

  25. Difference between Global and Local Variables: Global Variable Local Variable • The global variables can be used throughout the program. • All global variables in the absence of explicit initialization are automatically initialized to zero. Ex: int fact(int); main() { local variable declaration; } • Global variables get initialized only once typically. just before the program starts executing. • The local variables can be used only inside the function. • The scope or life time of the local variable is within a block or procedure. Ex: main() { int a,b,c; } • Local variables get initialized each time function or block gets called. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 25

  26. Recursion: Recursion is a repetitive process in which a function call itself directly or indirectly again and again is known as the recursion. The process of repetition can be done in two ways using programming. They are i) Iterative definition ii) Recursive definition Iterative Definition: Repeating a set of statements using loops is referred as iteration. Recursive Definition: A repetitive function is defined recursively whenever the function within the definition itself. The recursive function has two elements: each call either solves one part of the problem. The statement that size of the problem is known as the base case. The rest of the function is known as the general case. Each recursive function must have a best case. A recursive function is very useful to solve many mathematical problems like calculating the factorial of a number, generating Fibonacci series etc., To calculate n! the general formula as follows: n! = n*(n-1)! Fact(n)= 1 if n=0 base case n*fact(n-1) if n>0 general case Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 26

  27. Limitations of Recursion: ▪ Recursive solutions may involve extensive overhead because they use function calls. ▪ Each time you make a call, you use up some of your memory allocation. If recursion is deep, then you may run out of memory. Advantages of Recursion: • It is represent of loops. • The recursion is very flexible in data structure like stack, queue, linked list and quick sort. • Using recursion, the length of the program can be reduced. Syntax: #include<stdio.h> datatype function _name(datatype var1,…); int main() { ----- ---- function name(var1,..); ---------- return (result); } Syntax: #include<stdio.h> datatype var1,…); int main() { ----- ---- function name(var1,..); return 0; } 23-11-2023 function _name(datatype Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 27

  28. 9. Write a program to find factorial of a number using recursion #include<stdio.h> long int fact(int n); void main() { int n; long res; printf(“\n Enter the number:”); scanf(“%d”, &c); res=fact(n); printf(“\ n factorial of %d=%d”,n,res); } long int fact(int c) { if(n==1) return 1; Output: Enter the number: 6 Factorial of 6=720 else return n*fact(n-1); } Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 28

  29. 10. Write a program to find the factorial of a number using recursive function. #include<stdio.h> int factorial(int n); int fact=1; int main() { int n,fact; printf("Enter the n:"); scanf("%d",&n); fact=factorial(n); printf("%d",fact); return 0; } int factorial(int n) { if(n>0) { fact=fact*n; n=n-1; factorial(n); Output: Enter the n: 6 720 } return(fact); Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering } 23-11-2023 29

  30. Fibonacci series: fib(n)=1, if n=0 if n=1 fib(n-1)+fib(n-2), Otherwise. 11.Write a program to generate the Fibonacci series up to ‘n’ using recursive function. #include<stdio.h> int Fib(int n); void main() { int n, i , res; printf(" Enter the number of terms in Fibonacci series you need:"); scanf("%d",&n); printf("Fibonacci series\n"); for ( i = 0 ; i <= n ; i++ ) { res=fib(i); printf("%d\n", res); } } 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 30

  31. int fib(int n) { if ( n == 0 ) return 0; else if ( n == 1 ) return 1; else return (Fib(n-1) + Fib(n-2)); } Output: Enter the number of terms in Fibonacci series you need:8 Fibonacci series 0 1 1 2 3 5 8 13 21 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 31

  32. 12. Program to generate Fibonacci series using recursion #include<stdio.h> int Fibonacci(int, int); void main() { int n, i = 0, c; printf(" Enter the number of terms"); scanf("%d",&n); printf("Fibonacci series\n"); for ( c = 1 ; c <= n ; c++ ) { printf("%d\n", Fibonacci(i)); i++; } } 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 32

  33. int Fibonacci(int n) { if ( n == 0 ) return 0; else if ( n == 1 ) return 1; else return (Fibonacci(n-1) + Fibonacci(n-2)); } Output: Enter the number of terms8 Fibonacci series 0 1 1 2 3 5 8 13 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 33

  34. 13.WAPto find GCD and LCM of two numbers using concept of functions #include<stdio.h> int hcf(int, int); int main( ) { int x, y, gcd, lcm; printf("Enter two numbers"); scanf("%d%d", &x, &y); gcd = hcf(x, y); lcm = (x * y)/ gcd; printf("GCD = %d\n", gcd); printf("LCM = %d\n", lcm); } int hcf( int x, int y) { if(x == 0) return y; Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 34

  35. while(y!=0) { if(x > y) x = x-y; else y = y-x; } return x; } Output: Enter two numbers32 25 GCD = 1 LCM = 800 Enter two numbers3 45 GCD = 3 LCM = 45 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 35

  36. 14.Write a program to print sum of digits using recursion. #include<stdio.h> int sum(int n); void main() { int n; int res; printf(“\n Enter the number:”); scanf(“%d”, &n); res=sum(n); printf(“\n Number is= %d sum of the digit=%d”,n,res); } int sum(int n) { if(n==0) return 0; else return (n%10+sum(n/10)); } Output: Enter the number:234 n Number is= 234 sum of the digit=9 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 36

  37. STORAGE CLASSES : In ‘C’a variable can have any one of four Storage Classes. 1. Automatic Variables 2. External Variables 3. Static Variables 4. Register Variables SCOPE : The Scope of variable determines over what parts of the program a variable is actually available for use. LONGEVITY : • Longevity refers to period during which a variable retains a given value during execution of a program (alive). So Longevity has a direct effect on utility of a given variable. • The variables may also be broadly categorized depending on place of their declaration as internal(local) or external(global). Internal variables are those which are declared within a particular function, while external variables are declared outside of any function. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 37

  38. AUTOMATIC VARIABLES : • They are declared inside a function in which they are to be utilized. They are created when function is called and destroyed automatically when the function is exited, hence the name automatic. Automatic Variables are therefore private (or local) to the function in which they are declared. Because of this property, automatic variables are also referred to as local or internal variables. • By default declaration is automatic. One important feature of automatic variables is that their value cannot be changed accidentally by what happens in some other function in the program. #include<stdio.h> main() { int m=1000; func2(); printf(“%d\n”,m); } func1() { int m=10; printf(“%d\n”,m); } Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 38

  39. func2() { int m=100; func1(); printf(“%d”,m); } Output: 10 100 1000 • First, any variable local to main will normally live throughout the whole program, although it is active only in main. • Secondly, during recursion, nested variables are unique auto variables, a situation similar to function nested auto variables with identical names. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 39

  40. EXTERNAL VARIABLES : Variables that are both alive and active throughout entire program are known as external variables. They are also known as Global Variables. In case a local and global have same name local variable will have precedence over global one in function where it is declared. #include<stdio.h> int x; main() { x=10; printf(“%d”,x); printf(“x=%d”,fun1()); printf(“x=%d”,fun2()); } fun1() { x=x+10; return(x); } Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 40

  41. fun2() { int x; x=1; return(x); } fun3() { x=x+10; return(x); } Output: x=10 x=20 x=1 An extern within a function provides the type information to just that one function. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 41

  42. STATIC VARIABLES : The value of Static Variable persists until the end of program. A variable can be declared Static using Keyword Static like Internal & External Static Variables are differentiated depending whether they are declared inside or outside of auto variables, except that they remain alive throughout the remainder of program. #include<stdio.h> main() { int I; for (I=1;I<=3;I++) stat(); } stat() { static int x=0; Output: x=1 x=2 x=3 x=x+1; printf(“x=%d\n”,x); } Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 42

  43. REGISTER VARIABLES : We can tell the Compiler that a variable should be kept in one of the machines registers, instead of keeping in the memory. Since a register access is much faster than a memory access, keeping frequently accessed variables in register will lead to faster execution Syntax: register int Count. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 43

  44. List the storage class specifiers. Explain any one of them. OR Give the scope and lifetime of following: i. External variable ii. Static variable iii. Automatic variable iv. Register variable Variable External Variable/ Global Variable Definition The variables declared outside of all functions. Scope Global Lifetime Runtime of program Runtime of program Local The variables declared using static keyword. The variables declared inside the function. Static Variable Automatic Variable/ Local Variable Local Remains within the function in which it is declared. Register Variable The register keyword. variables declared using Local Remains within the block in which it is declared. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 44

  45. Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 45

  46. 15. Write a program to passing of array elements to function #include<stdio.h> void function(int n); void main() { int A[5],i; printf("Enter the elements of array"); for(i=0;i<5;i++) { scanf("%d",&A[i]); } printf("\n passing array element by element.."); for(i=0;i<5;i++) { function(A[i]); } } void function(int n) { printf("\n %d",n); } Output: Enter the elements of array9 2 5 6 7 passing array element by element.. 9 2 5 6 7 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 46

  47. 16. Write a program to pass the array elements by their references. #include<stdio.h> void Array(int A[]); void main() { int A[5],i; printf("Enter the elements of array"); for(i=0;i<5;i++) { scanf("%d",&A[i]); } printf("\n passing entire array"); Array(A); for(i=0;i<5;i++) { printf("\n After function call A[%d]:%d", i,A[i]); } } Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 47

  48. void Array(int A[]) { int i; for(i=0;i<5;i++) { A[i]=A[i]+10; } } Output: Enter the elements of array5 6 3 2 9 passing entire array After function call A[0]:15 After function call A[1]:16 After function call A[2]:13 After function call A[3]:12 After function call A[4]:19 23-11-2023 Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 48

  49. 17. WACP to find the largest element in an array. #include<stdio.h> void main( ) { int n, a[100], i,large=0; printf("Enter the size of array"); scanf("%d", &n); printf("Enter the elements of array"); for(i=0; i<n; i++) Output: Enter the size of array10 Enter the elements of array1 2 3 4 5 6 7 8 9 10 Largest number = 10 scanf("%d", &a[i]); for(i=0; i<n; i++) { if(a[i] >large) large = a[i]; } printf("Largest number = %d", large); } Mr Sreenu Banoth, Assistant Professor, Department of Computer Science and Engineering 23-11-2023 49

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