Introduction to c part 2

Recall
• Difference between while and do while?
• Difference between == and =
• Difference between break and continue?
• What is the difference between i++ and
++i
• What if i didn’t give break in switch?
• What is the difference between logical
operators and relational operators

Introduction to C
functions - Arrays – structures - pointers
Week 2- day 2

Functions
• A function is a group of statements that
together perform a task.
return_type function_name ( parameter list )
{
body of the function
}
Eg: main()
{
Printf(“hello world”);

Functions
int equation(int num1, int num2)
{
int result;
result = num1*num1+2*num1*num2+num2*num2;
return result;
}
Return Type
Function name
Arguments

#include<stdio.h>
int equation(int a, int b)
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Int main ()
{
int a,b,c;
Printf(“Enter the number”);
Scanf(“%d %d”,&a ,&b);
c = equation (a,b) ;
Printf(“%d”,c);
}

#include<stdio.h>
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Int main ()
{
int a,b,c;
c = equation (a,b) ; // Calling the function
Printf(“%d”,c);
}
//Function body / function Definition

#include<stdio.h>
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Int main ()
{
int a,b,c;
Printf(“%d”,c);
}
Should I use the same variable names?
Are they same of what I used in main() ?

#include<stdio.h>
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Int main ()
{
int a,b,c;
Printf(“%d”,c);
}
Absolutely not !!!
Variable a in equation() is different from
varaible a in main(). There is no
connection between those two

#include<stdio.h>
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Int main ()
{
int a,b,c;
Printf(“%d”,c);
}
What is this return???

#include<stdio.h>
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Int main ()
{
int a,b,c;
Printf(“%d”,c);
}
Return will simply send value out of
function to whomsoever it was called

#include<stdio.h>
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Int main ()
{
int a,b,c;
Printf(“%d”,c);
}
Can i write the whole function body after
main function??

#include<stdio.h>
int equation(int a, int b) ;
Int main ()
{
int a,b,c;
Printf(“%d”,c);
}
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
Yes you can. But only additional thing you
need to do is

#include<stdio.h>
int equation(int a, int b) ;
Int main ()
{
int a,b,c;
Printf(“%d”,c);
}
{
int c;
c= a*a+2*a*b+b*b;
return c;
}
You must declare it at the beginning

Arrays
• Is a collection of data of same type with
common name
• Eg: int a[6]
A[5]
A[4]
A[3]
A[2]
A[1]
A[0]
Memory
Each Cell will be size of int

Example
Main()
{
int a[10];
For(i=0;i<10;i++)
Scanf(“%d”,&a[i]);
For(i=0;i<10;i++)
printf(“%d”, a[i]);
}`

Strings in C
• There is no string data type in C
• But we can do the same with character
array in C
– Eg: char a[8] =“baabtra”//enables us to store
string with 6 characters
/0
A
R
T
B
A
A
B
A[7]
A[6]
a[5]
a[4]
a[3]
a[2]
a[1]
a[0]

main()
{
Char a[7]=“baabtra”; //Correct
Char *p=“baabtra”; //Correct
a=“baabtra”; //Incorrect
Scanf(“%s”,&a); //Correct
Scanf(“%s”, a); //Correct;But
why?? will discuss soon
Printf(“%s”,a);
}

Structures
• A structure is a collection of variables
under a single name
• These variables can be of different types,
and each has a name which is used to
select it from the structure.
struct struct_name
{
//Variable declarations;
}

Why structures?
• A structure is a convenient way of
grouping several pieces of related
information together.
• Eg: suppose there are several variables
called name,age,gender related to a
student . So we can bring all of them
under one name student using structures
• Eg: struct student
{
Char name[25];
Int age;

struct student
{
Char gender;
Int age;
}
main()
{
Struct student john,Mary;
John.age=15;
John.gender=“m”;
Mary.age=16;
Mary.gender=“f”;
}
age
gender
Student

Pointers
• Pointers simply points to locations in
memory
• Each variables will be having a address in
the memory. So pointer is just another
variable which simply stores the address
of it
Main()
{
int a,b, *p,*q;
1002
1001
25
99
1004
1003
1002
1001
q
p
b
a

Main()
{
int a,*p;
a=15;
P=&a;
Printf(“%d,%d ”,&a,p); // Will print 1001,1001
Printf (“%d, %d”,a,*p); // Will print 15,15
}
1001
15
1002
1001
p
a

Character array as pointer
Character array is a pointer to the first location of
a group of locations
Eg : char a[10];
Here a stores memory address of a[0]
main()
{
char a[10]="baabtra";
printf("%d %d",&a[0],a); // will print the
same address
A
R
T
B
A
A
B
A[6]
a[5]
a[4]
a[3]
a[2]
a[1]
a[0]
1006
1005
1004
1003
1002
1001
1000

Questions?
“A good question deserve a good
grade…”

Self - Check
#include<stdio.h>
Main()
{
Int a,b,c;
Printf(“Sum = %d”,sum(a,b));
}
Sum(int a,int b)
{
Return a+b;
}

Self - Check
#include<stdio.h>
Int sum(int a,int b)
Main()
{
Int a,b,c;
Printf(“Sum = %d”,sum(a,b));
}
Int sum(int a,int b)
{
Return a+b;
}

Self- Check
int main()
{
int a[5] = {5, 1, 15, 20, 25};
int i, j, m;
i = ++a[1];
j = a[1]++;
m = a[i++];
printf("%d, %d, %d", i, j, m);
return 0;
}
A.2, 1,
15
B.1, 2, 5
C.3, 2,
15
D.2, 3,

Self- Check
int main()
{
int a[5] = {5, 1, 15, 20, 25};
int i, j, m;
i = ++a[1];
j = a[1]++;
m = a[i++];
printf("%d, %d, %d", i, j, m);
return 0;
}
A.2, 1, 1
5
B.1, 2, 5
C.3, 2, 1
5
D.2, 3, 2

Self- Check
• A pointer to a block of memory is
effectively same as an array
A.True
B.False

Self- Check
Which of the following are themselves
a collection of different data types?
a) string
b) structures
c) char
d) All of the mentioned

Self- Check
Which of the following cannot
be a structure member?
a) Another structure
b) Function
c) Array
d) None of the mentioned

Self- Check
#include <stdio.h>
void main()
{
char *s= "hello";
char *p = s;
printf("%ct%c", p[0], s[1]);
}
a) Run time err
b) h h
c) h e
d) h l

Self- Check
#include<stdio.h>
struct course
{
int courseno;
char coursename[25];
};
int main()
{
struct course c[] = { {102, "Java"},
{103, "PHP"},
{104, "DotNet"} };
printf("%d ", c[1].courseno);
printf("%sn", (*(c+2)).coursename);
return 0;
}
A.103 DotNet
B.102 Java
C.103 PHP
D.104 DotNet

Self- Check
#include<stdio.h>
struct course
{
int courseno;
char coursename[25];
};
int main()
{
struct course c[] = { {102, "Java"},
{103, "PHP"},
{104, "DotNet"} };
printf("%d ", c[1].courseno);
printf("%sn", (*(c+2)).coursename);
return 0;
}
A.104 DotNet
B.102 Java
C.103 PHP
D.103 DotNet

Self- Check
#include <stdio.h>
void foo( int[] );
int main()
{
int ary[4] = {1, 2, 3, 4};
foo(ary);
printf("%d ", ary[0]);
}
void foo(int p[4])
{
int i = 10;
p = &i;
printf("%d ", p[0]);
}
a) 10 10
b) Compile time
c) 10 1
d) Undefined be

Self- Check
#include <stdio.h>
void foo( int[] );
int main()
{
int ary[4] = {1, 2, 3, 4};
foo(ary);
printf("%d ", ary[0]);
}
void foo(int p[4])
{
Int i=10;
p = &i;
printf("%d ", p[0]);
}
a) 10 10
b) Compile time
c) 10 1
d) Undefined be

Introduction to c part 2

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