EST 102 Programming in C-MODULE 4

Introduction to modular programming, writing functions, formal parameters, actual parameters .Pass by Value, Recursion, Arrays as Function Parameters ,structure, union, Storage Classes, Scope and life time of variables MODULE 4 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 1

Functions • A function is a group of statements that together perform a task. • Every C program has at least one function, which is main(). 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 2

Why to use Functions? • Development can be divided • Readable programs • Programming errors are easy to detect • Allows re-use of codes • Improves manageability • Collaboration 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 3

Types of Functions There are two types of functions in C programming: • Standard library functions • User-defined functions 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 4

Standard Library Functions • The standard library functions are built-in functions in C programming. • These functions are defined in header files. For example, • The printf() is defined in the stdio.h header file. • The sqrt() function is defined in the math.h header file. • The strlen() function is defined in the string.h header file.6/30/2020 NIMMY RAJU,AP,VKCET,TVM 5

User-defined function • User can also create functions as per their own needs. • Such functions created by users are known as user-defined functions. Advantages of user-defined function • easier to understand, maintain and debug. • Reusable codes • A large program can be divided among many programmers. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 6

• Three parts of a user defined functions are: – Function Declaration or Prototype – Function Definition – Function Call 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 7

Function Declaration or function prototype • A function prototype or function declaration is simply the declaration of a function that specifies function's name, parameters and return type. • It doesn't contain function body. • A function prototype gives information to the compiler that the function may later be used in the program. Syntax • return_type function_name( parameter list ); • int add(int a, int b);6/30/2020 NIMMY RAJU,AP,VKCET,TVM 8

Function Definition • A function definition in C programming consists of a function header and a function body. Here are all the parts of a function: Return Type: • A function may return a value. • The return_type is the data type of the value the function returns. • Some functions perform the desired operations without returning a value. • In this case, the return_type is the keyword void. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 9

Function Definition • Function Name: The actual name of the function. • Arguments: When a function is invoked, you pass a value to the parameter. This value is referred to as argument. • Function Body: The function body contains a collection of statements that define what the function does. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 10

• Syntax: return_type function_name( argument list ) { body of the function } 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 11

Function Call • When a program calls a function from the main function , the program control is transferred to the called function. • A called function performs a defined task and when its return statement is executed or when its function-ending closing brace is reached, it returns the program control back to the main program. Syntax: • functionName(parameter list); 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 12

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• Return Statement • The return statement terminates the execution of a function and returns a value to the calling function. • The program control is transferred to the calling function after the return statement. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 14

Types of user defined functions Types INPUT OUTPUT No arguments passed and no return value Sub function Sub function Arguments passed but no return value Main function Sub function No arguments passed but return value Sub function Main function Arguments passed with return value Main function Main function 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 15

Without function Using function(No arguments passed and no return value ) #include<stdio.h> void main() { int a,b,sum; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); sum=a+b; printf("Sum=%d",sum); } #include<stdio.h> void add(); void main() { add(); } // function to read two number and print its sum void add() { int a,b,sum; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); sum=a+b; printf("Sum=%d",sum); } Program to find the sum of two numbers 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 16

Without function Using function(arguments passed and no return value ) #include<stdio.h> void main() { int a,b,sum; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); sum=a+b; printf("Sum=%d",sum); } #include<stdio.h> void add(int ,int ); void main() { int a,b; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); add(a,b); } // function that takes two arguments and print their sum. void add(int a,int b) { int sum= a + b; printf("Sum=%d",sum); } Program to find the sum of two numbers 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 17

Without function Using function(No arguments passed and but return value ) #include<stdio.h> void main() { int a,b,sum; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); sum=a+b; printf("Sum=%d",sum); } #include<stdio.h> int add( ); void main() { int S; S=add(); printf("Sum=%d",S); } // function to read two number and return its sum int add() { int a,b,sum; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); sum = a+b; return sum; }6/30/2020 NIMMY RAJU,AP,VKCET,TVM 18

Without function Using function(arguments passed with return value ) #include<stdio.h> void main() { int a,b,sum; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); sum=a+b; printf("Sum=%d",sum); } #include<stdio.h> int add(int ,int ); void main() { int a,b,S; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); S=add(a,b); printf("Sum=%d",S); } // function that takes two arguments and print their sum. int add(int a,int b) { int sum; sum = a+b; return sum; } 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 19

No arguments passed and no return value No arguments passed and no return value No arguments passed and no return value No arguments passed and no return value #include<stdio.h> void large(); void main() { large(); } void large() { int a,b; printf("Enter the values of a & b"); scanf("%d%d",&a,&b) ; If(a>b) printf(“Largest=%d",a ); else printf(“Largest=%d“,a ); } #include<stdio.h> void large(int,int); void main() { int a,b; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); large(a,b); } void large(int x,int y) { If(x>y) printf(“Largest=%d",x); else printf(“Largest=%d“,y); } #include<stdio.h> int large(); void main() { int l; l=large(); printf(“Large=%d”,l); } int large() { int a,b; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); If(a>b) return a; else return b; } #include<stdio.h> int large(int,int); void main() { int a,b,l; printf("Enter the values of a & b"); scanf("%d%d",&a,&b); l=large(a,b); printf(“Large=%d”,l); int large(int a,int b) { If(a>b) return a; else return b; } Largest of two numbers 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 20

• Formal and Actual Parameters • Let us assume that a function B() is called from another function A(). • In this case A is called the “caller functionor calling function” and B is called the “called function or callee function”. • Also, the arguments which A sends to B are called actual arguments and the parameters of B are called formal arguments. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 21

• Formal Parameter: A variable and its type as they appear in the prototype of the function or method. • Actual Parameter: The variable or expression corresponding to a formal parameter that appears in the function or method call in the calling environment. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 22

Formal and Actual parameters  Let us assume that a function B() is called from another function A(). In this case A is called the “caller function or calling function” and B is called the “called function or callee function”.  The arguments which A sends to B are called actual arguments (parameters)and the arguments of B are called formal arguments(parameters).  Formal Parameter: A variable that appears in the prototype of the function.  Actual Parameter: The variable corresponding to a formal parameter that appears in the function call in the calling function. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 23

Example: #include<stdio.h> int swap(int a,int b); //function declaration void main() { int x=10,y=20; printf("Before swapping : x=%dty=%dn",x,y); swap(x,y); //function call printf("After swapping : x=%dty=%d",x,y); } int swap(int a,int b) //function definition { int temp=a; a=b; b=temp; printf("a=%dt b=%d",a,b); } Output Before swapping: x=10 y=20 a=20 b=10 After swapping : x=10 y=20 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 24

Pass by value(Call by value) • In this parameter passing technique, a copy of actual parameter is passed to formal parameter. • As a result, any changes or modification happened to formal parameter won’t reflect back to actual parameter 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 25

Example: #include<stdio.h> int swap(int a,int b); //function declaration void main() { int x=10,y=20; printf("Before swapping : x=%dty=%dn",x,y); swap(x,y); //function call –pass by value printf("After swapping : x=%dty=%d",x,y); } int swap(int a,int b) //function definition { int temp=a; a=b; b=temp; printf("a=%dt b=%d",a,b); } Output Before swapping: x=10 y=20 a=20 b=10 After swapping : x=10 y=20 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 26

Pass by reference(Call by reference) • Both the actual and formal parameters refer to same locations, so any changes made inside the function are actually reflected in actual parameters of caller. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 27

Example: #include<stdio.h> int swap(int *a,int *b); //function declaration void main() { int x=10,y=20; printf("Before swapping : x=%dty=%dn",x,y); swap(&x,&y); //function call –pass by reference printf("After swapping : x=%dty=%d",x,y); } int swap(int *a,int *b) //function definition { int temp=*a; *a=*b; *b=temp; printf("a=%dt b=%d",*a,*b); } Output Before swapping: x=10 y=20 a=20 b=10 After swapping : x=20 y=10 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 28

Recursive Function • A function that calls itself is known as a recursive function. And, this technique is known as recursion. • While using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop. • Recursion makes program elegant. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 29

Write a program to find factorial of number using recursive function #include<stdio.h> int fact(int n) { if( n == 0) return 1; return n*fact(n-1); } void main() { int n,f; printf("Enter the number:"); scanf("%d",&n); f-=fact(n); printf("factorial=%d",f); } Output Enter the number:5 factorial=120 fact(5) fact(4) fact(3) fact(2) fact(1) fact(0) fact(5) { return 5*fact(4); } fact(4) { return 4*fact(3); } fact(3) { return 3*fact(2); } fact(2) { return 2*fact(1); } fact(1) { return 1*fact(0); } fact(0) { return 1; } 5*24=120 4*6=24 3*2=6 2*1=2 1*1=1 1 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 30

Write a program to find sum of first n natural numbers using recursive function #include<stdio.h> int sum(int n) { if( n == 0) return 0; return n+sum(n-1); } void main() { int n,f; printf("Enter the limit:"); scanf("%d",&n); printf(“n Sum=%d",sum(n)); } Output Enter the limit:5 factorial=15 sum(5) sum(4) sum(3) sum(2) sum(1) sum(0) sum(5) { return 5+sum(4); } sum(4) { return 4+sum(3); } sum(3) { return 3+sum(2); } sum(2) { return 2+sum(1); } sum(1) { return 1+sum(0); } sum(0) { return 0; } 5+10=15 4+6=10 3+3=6 2+1=3 1+0=1 0 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 31

Passing an array as Parameter  Like the value of simple variables, it is also possible to pass the values of an array to a function.  To pass a single dimensional array to a function, it is sufficient to list the name of the array without any subscripts and the size of the array as arguments 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 32

Rules to pass an Array to Function  The function must be called by passing only the name of the array.  In function definition, formal parameter must be an array type; the size of the array does not need to be specified.  The function prototype must show that the argument is an array. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 33

Write a function to sort an array. #include<stdio.h> int sort(int A[],int n) { int i,j,temp; for(i=0;i<n-1;i++) { for(j=0;j<n-i-1;j++) { if(A[j]>A[j+1]) { temp = A[j]; A[j] = A[j+1]; A[j+1]= temp; } } } void main() { int A[30],i,n; printf("Enter the limit:"); scanf("%d",&n); for(i=0;i<n;i++) { printf("Enter the element:"); scanf("%d",&A[i]); } sort(A,n); printf("Sorted Arrayn"); for(i=0;i<n;i++) printf("%dt",A[i]); } Output Enter the limit:5 Enter the element:17 Enter the element:23 Enter the element:5 Enter the element:2 Enter the element:9 Sorted Array 2 5 9 17 23 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 34

• Passing 2 D array as parameter • While passing 2D as parameter we need to mention the max size of element of each row that is column 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 35

Write a program to pass a 2 D matrix as parameter and find its sum of all the elements #include<stdio.h> // function that takes a 2 D and its order int sum(int A[][30],int m,int n) { int i,j,sum =0; for(i=0;i<m;i++) { for(j=0;j<n;j++) { sum = sum + A[i][j]; } } printf("Sum=%d",sum); } } void main() { int A[30][30]; int i,n,m,j; printf("Enter the order of matrix:"); scanf("%d%d",&m,&n); for(i=0;i<m;i++) { for(j=0;j<n;j++) { printf("Enter the element:"); scanf("%d",&A[i][j]); } } sum(A,m,n); } Output Enter the order of matrix:2 2 Enter the element:1 Enter the element:2 Enter the element:3 Enter the element:4 Sum=10 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 36

STRUCTURE • A structure is a user defined data type in C. • A structure creates a data type that can be used to group items of possibly different types into a single type. • ‘struct’ keyword is used to create a structure. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 37

• Consider we want to create the structure of a person with following variable name, age and address. • Then such a structure can be created as struct Person { char name[30]; int age; char addr[50]; }p; 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 38

The general format of a structure definition is as follows struct structure_name { data_type member1; data_type member2; --------------------- --------------------- }S; Here S is called structure variable.6/30/2020 NIMMY RAJU,AP,VKCET,TVM 39

• A structure variable can either be declared with structure declaration or as a separate declaration like basic types. struct structure_name { data_type member1; data_type member2; --------------------- --------------------- }: void main() { struct structure_name S; } struct structure_name { data_type member1; data_type member2; --------------------- --------------------- }S; 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 40

Declare a structure namely Student to store the details (roll number, name, mark_for_C) of two students and display the data. #include<stdio.h> struct Student { char name[30]; int rollnum; int mark; }; void main() { struct Student s1,s2; printf("Enter the Student name:"); scanf("%s",s1.name); printf("Enter the Student rollnum:"); scanf("%d",&s1.rollnum); printf("Enter the Student Mark for C:"); scanf("%d",&s1.mark); printf("Enter the Student name:"); scanf("%s",s2.name); printf("Enter the Student rollnum:"); scanf("%d",&s2.rollnum); printf("Enter the Student Mark for C:"); scanf("%d",&s2.mark); printf("NametRoll NumbertMark for Cn"); printf("%st%dt%dn",s1.name,s1.rollnum,s1.m ark); printf("%st%dt%dn",s2.name,s2.rollnum,s2.m ark); } Output Enter the Student name:Sangeeth Enter the Student rollnum: Enter the Student Mark for C:35 Enter the Student name:Pratheesh Enter the Student rollnum:24 Enter the Student Mark for C:40 Name Roll Number Mark for C Sangeeth 27 35 Pratheesh 24 40 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 41

Array of Structures  DeclareastructurenamelyStudenttostorethedetails(roll number, name, mark_for_C) of a student. Then, write a program in C to find the average mark obtained by the students in a class for the subject Programming in C (using the field mark_for_C). Use array of structures to store the required data. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 42

Declare a structure namely Student to store the details (roll number, name, mark_for_C) of two students and display the data. #include<stdio.h> struct Student { char name[30]; int rollnum; int mark; }; void main() { struct Student s1,s2; printf("Enter the Student name:"); scanf("%s",s1.name); printf("Enter the Student rollnum:"); scanf("%d",&s1.rollnum); printf("Enter the Student Mark for C:"); scanf("%d",&s1.mark); printf("Enter the Student name:"); scanf("%s",s2.name); printf("Enter the Student rollnum:"); scanf("%d",&s2.rollnum); printf("Enter the Student Mark for C:"); scanf("%d",&s2.mark); printf("NametRoll NumbertMark for Cn"); printf("%st%dt%dn",s1.name,s1.rollnum,s1.m ark); printf("%st%dt%dn",s2.name,s2.rollnum,s2.m ark); } Output Enter the Student name:Sangeeth Enter the Student rollnum: Enter the Student Mark for C:35 Enter the Student name:Pratheesh Enter the Student rollnum:24 Enter the Student Mark for C:40 Name Roll Number Mark for C Sangeeth 27 35 Pratheesh 24 40 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 43

#include<stdio.h> struct Student { char name[30]; int rollno; int mark_for_C; }; void main() { struct Student s[30]; int i,n,sum=0; float avg; printf("Enter the no of Student:"); scanf("%d",&n); for(i=0;i<n;i++) { printf("Enter the Student name:"); scanf("%s",s[i].name); printf("Enter the Student rollno:"); scanf("%d",&s[i].rollno); printf("Enter the Mark for C:"); scanf("%d",&s[i].mark_for_C); } printf("NametRoll NumbertMark for Cn"); for(i=0;i<n;i++) { printf("%st%dt%dn",s[i].name, s[i].rollnum,s[i].mark_for_C); sum = sum + s[i].mark_for_C; } avg = (float)sum /n; printf("Average Mark=%fn",avg); } 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 44

Output Enter the no of Student:3 Enter the Student name:Sangeeth Enter the Student rollnum:27 Enter the Student Mark for C:35 Enter the Student name:Pratheesh Enter the Student rollnum:24 Enter the Student Mark for C:40 Enter the Student name:Poornima Enter the Student rollnum:26 Enter the Student Mark for C:45 Name Roll Number Mark for C Sangeeth 27 35 Pratheesh 24 40 Poornima 26 45 Average Mark=40.00 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 45

UNION  A union is a user-defined type similar to struct in C programming.  We use the union keyword to define unions. Example of Employee Union creation and declartion union Employee { char name[30]; int age; double salary; }; union Employee e; 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 46

Difference between structure and union Structure Union struct keyword is used to define a structure union keyword is used to define a union Members do not share memory in a structure. Members share the memory space in a union Any member can be retrieved at any time in a structure Only one member can be accessed at a time in a union. Several members of a structure can be initialized at once. Only the first member can be initialized. Sizeofthestructureisequalto thesumofsize of the each member. Size of the union is equal to the size of the largest member. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 47

#include<stdio.h> struct Person { char pincode[6]; // Size = 6 bytes int age; // Size = 4 bytes double salary;// Size = 8 bytes }; union Employee { char pincode[6]; int age; double salary; }; void main() { struct Person p; union Employee e; printf("Size of Structure Person=%dn",sizeof(p)); printf("Size of Union Employee=%d",sizeof(e)); } Output Size of Structure Person=18 Size of Union Employee=86/30/2020 NIMMY RAJU,AP,VKCET,TVM 48

Storage Classes, Scope and life time of variables 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 49

• In C, not only do all the variables have a data type, they also have a storage class. • The following variable storage classes are most relevant to functions – Automatic Variables – External or Global Variables – Static Variables – Register Variables 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 50

Automatic Variables • Automatic variables are declared inside a function in which they are to be utilized. • They are created when the 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. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 51

Automatic Variables • A variable declared inside a function without storage class specification is by default an automatic variable. void main() { int num; } is same as void main() { auto int num; } 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 52

• Example #include<stdio.h> void func1() { int max=10; printf("Max in func1()=%dn",max); } void func2() { int max=20; printf("Max in func2()=%dn",max); } void main() { int max=30; func1(); func2(); printf("Max in main()=%dn",max); } Output Max in func1()=10 Max in func2()=20 Max in main()=30 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 53

External Variables • Variables that are both alive and active throughout the entire program are known as external variables. • They are called global variables. • Unlike local variables, global variables can be accessed by any function in the program. • External global variables are global variables visible to all file other than in which it is declared6/30/2020 NIMMY RAJU,AP,VKCET,TVM 54

#include<stdio.h> int max; void func1() { printf("Max in func1()=%dn",max); } void func2() { printf("Max in func2()=%dn",max); } void main() { max=30; func1(); func2(); printf("Max in main()=%dn",max); } Max in func1()=30 Max in func1()=30 Max in main()=30 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 55

Static Variables • As the name suggests, the value of static variables persists until the end of the program. • A variable can be declared static using the keyword static like static int x; • Static global variables are global variables visible only to the file in which it is declared. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 56

Register Variables • We can tell the compiler that a variable should be kept in one of the machine’s registers instead of keeping in the memory. • Since a register access is fast than a memory access, keep in the frequently accessed variables in the register will lead to faster execution of programs. • This is done as follows register int count; 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 57

• The scope of a variable is the part of the program within which the variable can be used. So, the scope describes the visibility of an identifier within the program. • The lifetime of a variable or function is the time duration for which memory is allocated to store it, and when that memory is released. 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 58

StorageClass Wheredeclared Visibility Lifetime extern Beforeallfunctionsinafile Entire file plus other files where variable is declared. Global Static Beforeallthefunctioninafile Onlyinthatfile Global Noneorauto Inside afunction Only in that function orblock Until end of function Register Inside afunctionorblock Onlyinthatfunction orblock Until end of function 6/30/2020 NIMMY RAJU,AP,VKCET,TVM 59

EST 102 Programming in C-MODULE 4

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EST 102 Programming in C-MODULE 4