1) The document discusses structures in C programming, which allow grouping of related data types into a single data type. 2) A structure called student is defined containing member variables like rollnumber, semnumber, and age_years. A variable of this structure type is initialized and its members are accessed. 3) Structures can contain other structures to represent nested relationships between data. They provide a way to organize and manage related data in an application.

1. Computing Fundamentals
Dr. Muhammad Yousaf Hamza
Deputy Chief Engineer, PIEAS

2. STRUCTURES
Dr. Yousaf, PIEAS

3. //Structures //Collection of various types of variables
#include <stdio.h>
struct student //declares a structure
{
int rollnumber;
int semnumber;
double age_years;
}; // See the use of semicolon
int main()
{
struct student student1; /*defines a variable student1 of type structure*/
student1.rollnumber = 15;
student1.semnumber = 1;
student1.age_years = 18.5;
//Print the structure members
printf("Roll Nomber = %dn",student1.rollnumber);
printf("Semesetr Number = %dn",student1.semnumber);
printf("Age = %lfn",student1.age_years);
getchar(); return 0; }
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4. • They make your programming easier.
• You can extend the language - for example, if you use
complex numbers a lot then you can write structures
and functions which deal with complex numbers.
• Structures are C’s way of grouping collections of
data into a single manageable unit.
– This is also the fundamental element of C upon which
most of C++ is built (i.e., classes).
– Similar to Java's classes.
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Structures

5. Structures
• struct is used to describe a new data type.
• int, double and char are types of variables.
With struct you can create your own. It is a
new way to extend the C programming language.
• If programmers do a good job of this, the end
user doesn't even have to know what is in the
data type.
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6. Structures
• An example:
– Defining a structure type:
struct student //declares a structure
{
int rollnumber;
int semnumber;
double age_years;
};
• This defines a new type struct student.
• No variable is actually declared or generated.
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7. #include <stdio.h>
//group things together
struct database
{
int id_number;
int age;
float salary;
};
int main()
{
struct database employee;
employee.age = 22;
employee.id_number = 1;
employee.salary = 12000.21;
}
Structures
Dr. Yousaf, PIEAS

8. #include <stdio.h>
//group things together
struct database
{
int id_number;
int age;
float salary;
};
int main()
{
struct database employee;
employee.age = 22;
employee.id_number = 1;
employee.salary = 12000.21;
}
Structures
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• Members of the structure
• No space in memory
• Accessing the members of
structure using Dot operator

9. // Program using Concept of
Structures
#include <stdio.h>
struct student //declares a structure
{
int rollnumber;
int semnumber;
double age_years;
}; // See the use of semicolon
int main()
{
struct student student1;
/*defines a variable student1 of
type structure */
struct student student2;
student1.rollnumber = 15;
student1.semnumber = 1;
student1.age_years = 18.5;
//Print the structure members
printf("Roll Nomber =
%dn",student1.rollnumber);
printf("Semesetr Number =
%dn",student1.semnumber);
printf("Age = %lfn",
student1.age_years);
student2.rollnumber = 22;
student2.semnumber = 1;
//Print the structure members
printf("nnRoll Nomber =
%dn",student2.rollnumber);
printf("Semesetr Number =
%dn",student2.semnumber);
getchar(); return 0;
}
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10. /*More features of structures
Initialization of member variables
Program using Concept of
Structures*/
#include <stdio.h>
struct student //declares a structure
{
int rollnumber;
int semnumber;
double age_years;
}; // See the use of semicolon
int main()
{
struct student student1 =
{15,1,18.5}; /*defines a variable
student1 of type structure */
struct student student2;
//Print the structure members
printf("Roll Nomber =
%dn",student1.rollnumber);
printf("Semesetr Number =
%dn",student1.semnumber);
printf("Age =
%lfn",student1.age_years);
student2 = student1;
//Print the structure members
printf("nnRoll Nomber =
%dn",student2.rollnumber);
printf("Semesetr Number =
%dn",student2.semnumber);
printf("Age =
%lfn",student1.age_years);
getchar();
return 0;
}
Dr. Yousaf, PIEAS

11. /*More features of structures
Initialization of member variables
Program using Concept of
Structures*/
#include <stdio.h>
struct student //declares a structure
{
int rollnumber;
int semnumber;
double age_years;
} student1, student2;
int main()
{
student1 = {15,1,18.5}; /*defines
a variable student1 of type
structure */
//Print the structure members
printf("Roll Nomber =
%dn",student1.rollnumber);
printf("Semesetr Number =
%dn",student1.semnumber);
printf("Age =
%lfn",student1.age_years);
student2 = student1;
//Print the structure members
printf("nnRoll Nomber =
%dn",student2.rollnumber);
printf("Semesetr Number =
%dn",student2.semnumber);
printf("Age =
%lfn",student1.age_years);
getchar();
return 0;
}
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12. • Define struct variables:
struct coord
{
int x,y ;
} first, second;
• Another Approach:
struct coord
{
int x,y ;
};
...............
struct coord first, second, third; /* declare variables */
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Structures

13. • Access structure variables by the dot (.) operator
• Generic form:
structure_var.member_name
• For example:
first.x = 50 ;
second.y = 100;
• These member names are like the public data members
of a class in Java (or C++).
– No equivalent to function members/methods.
• struct_var.member_name can be used anywhere a
variable can be used:
– printf ("%d , %d", second.x , second.y );
– scanf("%d, %d", &first.x, &first.y);
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Structures

14. • You can assign structures as a unit with =
first = second;
instead of writing:
first.x = second.x ;
first.y = second.y ;
• Although the saving here is not great
– It will reduce the likelihood of errors and
– Is more convenient with large structures
• This is different from Java where variables are simply
references to objects.
first = second;
makes first and second refer to the same object.
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Structures

15. /* Addition of lengths using
concept of structures*/
#include <stdio.h>
struct AddLength
{
int feet;
float inches;
}; // See the use of semicolon
int main()
{
struct AddLength d1, d2, d3;
int carry;
puts("This program adds two
values of lengths");
puts("Enter the value of length in
feet and inches");
puts("Enter the value of feet
for first length");
scanf("%d", &d1.feet);
puts("Enter the value of inches
for first length");
scanf("%f", &d1.inches);
puts("Enter the value of feet
for second length");
scanf("%d", &d2.feet);
puts("Enter the value of inches
for second length");
scanf("%f", &d2.inches);
// continued to next slide
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16. d3.inches = d1.inches + d2.inches;
carry = 0;
if (d3.inches >=12.0)
{
d3.inches -= 12.0;
carry++;
}
d3.feet = d1.feet + d2.feet + carry;
//Print the structure members
printf("First length = %d feet %f inchesn", d1.feet,d1.inches);
printf("Second length = %d feet %f inchesn", d2.feet,d2.inches);
printf("Addition of lengths = %d feet %f inchesn", d3.feet,d3.inches);
getchar();
return 0;
}
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17. • C program to add, subtract, multiply and divide
Complex Numbers
• C Program to add, subtract, multiply and divide
complex numbers :- This program performs basic
operations on complex numbers i.e addition,
subtraction, multiplication and division. This is a
menu driven program in which user will have to
enter his/her choice to perform an operation. User
can perform operations until desired. To easily
handle a complex number a structure named
complex has been used, which consists of two
integers first integer is for real part of a complex
number and second for imaginary part.
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18. // C programming code for addition of
complex numbers
#include<stdio.h>
#include<stdlib.h>
struct complex
{
int real, img;
};
int main()
{
struct complex c1, c2, c3;
printf("Enter a and b where a + ib is the
first complex number.");
printf("na = ");
scanf("%d", &c1.real);
printf("b = ");
scanf("%d", &c1.img);
printf("Enter c and d where c + id is
the second complex number.");
printf("nc = ");
scanf("%d", &c2.real);
printf("d = ");
scanf("%d", &c2.img);
c3.real = c1.real + c2.real;
c3.img = c1.img + c2.img;
if ( c3.img >= 0 )
printf("Sum of two complex numbers
= %d + %di",c3.real,c3.img);
else
printf("Sum of two complex numbers
= %d %di",c3.real,c3.img);
getchar();
return 0;
}
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19. Solve a Problem
To represent a complex number, write a structure
complexNum , decide the members of the structure
and their type, create two variables of type
complexNum and initialize them from user input,
check whether the number are equal or not?
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20. What else can we do with structs?
We can pass and return structs to/from
functions. But make sure the function prototype
is _AFTER_ the struct is declared.
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21. /*Multiplication of complex numbers through function
using the concept of structures*/
struct complex
{
float imag;
float real;
};
complex mult_complex (complex no1, complex no2);
int main()
{
/* Main goes here */
}
// Definition of function
complex mult_complex (complex no1, complex no2)
{
struct complex answer;
answer.real= no1.real*no2.real - no1.imag*no2.imag;
answer.imag= no1.imag*no2.real + no1.real*no2.imag;
return answer;
} Dr. Yousaf, PIEAS

22. /*Multiplication of complex numbers through function
using the concept of structures*/
typedef struct complex
{
float imag;
float real;
} CPLX;
CPLX mult_complex (CPLX, CPLX);
int main()
{
CPLX n1,n2;
/* Main goes here */
}
// Definition of function
CPLX mult_complex (CPLX no1, CPLX no2)
{
CPLX answer;
answer.real= no1.real*no2.real - no1.imag*no2.imag;
answer.imag= no1.imag*no2.real + no1.real*no2.imag;
return answer;}
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The typedef keyword is
used to create a new name
for an existing data type. In
fact, typedef creates a
synonym.
When typedef is used in
structure definition, then
don’t write struct for
variables declaration.

23. /*Multiplication of complex numbers through function
using the concept of structures*/
typedef struct // even no name here also works
{
float imag;
float real;
} CPLX;
CPLX mult_complex (CPLX, CPLX);
int main()
{
CPLX n1,n2;
/* Main goes here */
}
CPLX mult_complex (CPLX no1, CPLX no2)
{
CPLX answer;
answer.real= no1.real*no2.real - no1.imag*no2.imag;
answer.imag= no1.imag*no2.real + no1.real*no2.imag;
return answer; Dr. Yousaf, PIEAS

24. Structures Containing Arrays
• Arrays within structures are the same as any other
member element.
• For example:
struct record
{
float x;
char y [5] ;
} ;
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25. An Example
#include <stdio.h>
struct data
{
float amount;
char fname[30];
char lname[30];
} rec;
int main ()
{
struct data rec;
printf ("Enter the donor's first and last names, n");
printf ("separated by a space: ");
scanf ("%s %s", rec.fname, rec.lname);
printf ("nEnter the donation amount: ");
scanf ("%f", &rec.amount);
printf ("nDonor %s %s gave $%.2f.n", rec.fname,rec.lname,rec.amount);
}
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26. Arrays of Structures
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27. Arrays of Structures
• The converse of a structure with arrays:
• Example:
struct entry
{
char fname [10] ;
char lname [12] ;
char phone [8] ;
} ;
struct entry list [1000];
• This creates a list of 1000 identical entry(s).
• Assignments:
list [1] = list [6];
strcpy (list[1].phone, list[6].phone);
list[6].phone[1] = list[3].phone[4] ;
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28. Initializing Structures
• Simple example:
struct sale
{
char customer [20] ;
char item [20] ;
int amount ;
};
struct sale mysale = { “Mr. XYZ", “Biscuits", 10000 } ;
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29. Initializing Structures
• Structures within structures:
struct customer
{
char firm [20] ;
char contact [25] ;
};
struct sale
{
struct customer buyer ;
char item [20] ;
int amount ;
} mysale =
{ { “Shaheen Industries", “Mr. XYZ"} ,
“Biscuits", 10000
} ;
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30. // An Example
#include <stdio.h>
struct employee
{
char fname [20];
char lname [20];
char phone [10];
} ;
int main()
{
struct employee list[4];
int i;
for (i=0; i < 4; i++)
{
printf(Enter the data of employee %d:”, i+1)
printf ("nEnter first name: ");
scanf ("%s", list[i].fname);
printf ("Enter last name: ");
scanf ("%s", list[i].lname);
printf ("Enter phone in 123-4567 format: ");
scanf ("%s", list[i].phone);
}
printf ("nn");
for (i=0; i < 4; i++)
{
printf ("Name: %s %s", list[i].fname,
list[i].lname);
printf ("ttPhone: %sn", list[i].phone);
}
} Dr. Yousaf, PIEAS

31. Nested Structures
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32. // Example of Nested structures
#include <stdio.h>
struct Distance
{
int feet;
float inches;
}; // observe the semicolon
struct Room //rectangular room
{
struct Distance length; //length of room
struct Distance width; //width of room
};
int main()
{
float l,w;
struct Room dining; /*dining is
of type Room*/
dining.length.feet = 13;
dining.length.inches = 6.5;
dining.width.feet = 10;
dining.width.inches = 0.0;
//convert length & width
l=dining.length.feet+
dining.length.inches/12;
w=dining.width.feet+
dining.width.inches/12;
//find area and display it
printf("Dining room area is %f
square feetn",l*w);
return 0; }
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33. • Accessing nested Structured Members
dining.length.feet = 13;
• Initializing Nested Structures
Room dining = { {13, 6.5}, {10, 0.0} };
• Depth of Nesting
apartment1.laundry_room.washing_machine.width.feet
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Nested Structures