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Functions in C 7
Example 7.1 A
C program using a function.
Answer:
#include<stdio.h>
int sum (int
a, int b);
int main()
{
int a = 4, b
= 5, result;
result=sum(a,b);
printf(“\n
result is: %d”, result);
return 0;
}
int sum(int
a, int b)
{
int
result=a+b;
return
result;
}
Meaning:
It looks like you've
provided a standard C program that demonstrates the complete lifecycle of a
function. This code is a great example of modular programming,
where the logic for addition is separated from the main execution.
Breakdown of your code:
1.
Prototype: int
sum (int a, int b); — This alerts the
compiler that a function named sum exists and expects two integers.
2.
Arguments
vs. Parameters:
o
In main(), a and b are Actual Arguments (the real values being sent).
o
In sum(), a and b are Formal Parameters (local variables that receive the
values).
3.
Scope: Notice that you have a variable named result in both main() and sum(). Because of local scope, these are two completely different
containers in memory; the result inside sum only exists until the function returns.
A Small Correction for Clean Execution
Your code is logically
perfect, but there is one tiny typographical detail to watch out for: the quotation marks in your printf statement.
In C programming, you
must use straight quotes ("...") rather than "smart" or curly
quotes (“...”), which often appear if you copy-paste from a
word processor.
Here is the corrected version
of your snippet:
C
#include <stdio.h>
int sum(int a, int b); // Prototype
int main() {
int a = 4, b = 5, result;
// The value returned by sum() is stored in the local 'result'
result = sum(a, b);
// Fixed the quotation marks here:
printf("\n result is: %d",
result);
return 0;
}
int sum(int a, int b) {
int result = a + b;
return result; // Value 9 is sent back to main
}
Execution Flow
1.
main starts and initializes a=4 and b=5.
2.
main pauses and jumps to sum().
3.
sum creates its own a and b, calculates 9, and
"hands" it back to main.
4.
main resumes, stores that 9 in its own result variable, and prints
it.
Would you like to see
how you can make this function even shorter using a single-line
return statement?
Based on the code you
provided, the program will calculate the sum of the two integers and display
the result on the screen.
The Output
Plaintext
result is: 9
Execution Trace
To understand how the
computer arrived at 9, here is the step-by-step trace
of the memory and execution:
1.
Initialization: The variables a and b in main() are assigned 4 and 5.
2.
The
Call: When sum(a, b) is called, the values
are passed into the function.
3.
The
Calculation: Inside the sum function, a local
variable result is created. It calculates $4 + 5$, resulting
in 9.
4.
The
Return: The value 9 is "thrown" back to the main() function.
5.
The
Assignment: In main(), the result variable receives
that 9.
6.
The
Print: The printf statement outputs the
final value.
Common "Gotcha" with this Output
If you were to change
the values of a or b inside the sum function, the a and b in main would not change. This is because C uses Pass by Value, meaning the function only gets a copy of the numbers, not the original variables
themselves.
Would you like me to
show you how the output changes if we use user input via scanf
instead of fixed numbers?
Example 7.1 A
C program using a function.
Finding summation of two numbers:
Let
us write a function to find the summation of two integers.
Answer:
#include<stdio.h>
int sum (int a, int b);
int main()
{
int a, b, result;
printf("\n Enter the first number: ");
scanf("%d", &a);
printf("\n Enter the second number: ");
scanf("%d", &b);
result = sum(a, b);
printf("\n Result is: %d", result);
return 0;
}
int sum(int a, int b)
{
int result;
result = a + b;
return result;
}
Meaning:
This C program calculates the sum of
two user-inputted integers using a custom function
. It prompts for two numbers, adds
them via the sum
function, and prints the result. Based on input 5 and 10, the output will
be:
text
Enter the first number: 5
Enter the second number: 10
Result is: 15
Step-by-step Execution:
- Enter the first number: is printed.
- The program waits for user input (e.g., 5).
- Enter the second number: is printed.
- The program waits for user input (e.g., 10).
- sum(5, 10)
returns
5+10=155
plus 10 equals 15
5+10=15
.
- Result is: 15
is printed.
This C program
calculates the sum of two user-inputted integers using a custom function. It
defines sum(int
a, int b), which adds two
numbers and returns the result to the main() function. The program then prints the final sum.
Code Breakdown:
·
#include<stdio.h>: Includes the standard I/O library for printf and scanf.
·
int sum(int a, int b);: Function prototype (declaration).
·
main(): Executes input,
calls sum, and prints the output.
·
scanf("%d", &a);: Reads integer input from the user.
·
sum(a, b):
Function call to calculate the sum.
·
return result;: Returns the calculated sum, a + b, to the caller.
Execution Example:
text
Enter the first number: 5
Enter the second number: 10
Result is: 15
Example 7.2 A C program using a function with extra printf().
Answer:
#include<stdio.h>
int sum (int a, int b);
int main()
{
int a, b, result;
printf("\n Enter the first number: ");
scanf("%d", &a);
printf("\n Enter the second number: ");
scanf("%d", &b);
printf("\n Program control: just before making function
call.");
result = sum(a, b);
printf("\n Program control: just after return from function
call.");
printf("\n Result is: %d", result);
return 0;
}
int sum(int a, int b)
{
printf("\n Program control: inside function
definition.");
int result;
result = a + b;
return result;
}
Meaning
& Output
The provided C program
prompts for two integers, displays execution control flow messages, calculates
their sum using a function, and outputs the final result. Assuming user input
is 5 and 3, the output shows the sequence of printf statements, the function call, and the
final result.
Example Output:
text
Enter the first number: 5
Enter the second number: 3
Program control: just before making function
call.
Program control: inside function definition.
Program control: just after return from
function call.
Result is: 8
Breakdown:
This C program calculates
the sum of two user-inputted integers using a custom function. It defines sum to add two integers and calls it
from main, printing debug messages to show the program
flow: from main, into the function, and back to main to display the result.
Program Flow &
Output Example:
If the user inputs 5 and 10, the output will be:
text
Enter the first number: 5
Enter the second number: 10
Program control: just before making function
call.
Program control: inside function definition.
Program control: just after return from
function call.
Result is: 15
Key Components:
·
Function
Prototype: int sum (int a, int
b); declares the
function before it is used.
·
Function
Call: result = sum(a, b); passes user inputs to the function.
·
Function
Definition: int sum(int a, int b)
{ ... } receives
parameters, calculates $a + b$, and returns the
result.
·
Control
Flow: The printf statements before/after sum(a,b) and inside the function demonstrate the
execution order.
Example 7.3: A C program for finding the largest among three
numbers using a function.
Answer:
#include<stdio.h>
int find_largest (int a, int b, int c);
int main()
{
int a, b, c, largest = 0;
printf("\n Enter the first number: ");
scanf("%d", &a);
printf("\n Enter the second number: ");
scanf("%d", &b);
printf("\n Enter the third number: ");
scanf("%d", &c);
largest = find_largest(a, b, c);
printf("\n Largest number is: %d", largest);
return 0;
}
int find_largest ( int a, int b, int c )
{
int largest = 0;
if ( a > b )
{
if ( a > c )
largest = a;
else
largest = c;
}
else
{
if ( b > c )
largest = b;
else
largest = c;
}
return largest;
}
Meaning
and Output:
The provided C code
prompts the user to enter three numbers. The output will vary depending on the
numbers the user enters.
Here is an example of
the program's execution and output, assuming the user enters 10, 45, and 20:
Enter the first number: 10
Enter the second number: 45
Enter the third number: 20
Largest number is: 45
If you run the program
and enter different values, the final output will display the largest of those
three numbers.
The provided C code is
a complete and working program designed to find the largest of three numbers
entered by the user.
Code Description
The program consists
of two main functions:
1.
main(): This function
handles user input using printf and scanf, calls the find_largest function to determine the maximum value,
and then prints the final result.
2.
find_largest(int a, int b, int c): This function accepts three integer arguments and uses a
series of nested if-else statements to
compare the numbers and return the largest one.
Analysis of the Logic
The logic within
the find_largest function effectively determines the
largest number by comparing the values in a structured way:
·
It first checks
if a is greater than b.
o If true, it compares a with c to find the largest between the two.
o If false, it means b is greater than or equal to a, so it proceeds to compare b with c.
Alternative Implementation
The logic can be
simplified using the ternary operator, which is more concise for this type of
problem:
c
int
find_largest_simplified ( int a, int b, int c )
{
// Compares a and b, then compares the
larger of the two with c
int largest = (a > b) ? (a > c
? a : c) : (b > c ? b : c);
return largest;
}
Example 7.4: A C program for finding the largest among a series
of numbers.
Answer:
#include<stdio.h>
int find_largest (int);
int number[20];
int main()
{
int totalEle, largest = 0;
printf("\n Enter total number of elements in the series:
");
scanf("%d", &totalEle);
printf("\n Taking input to the array elements: ");
for(int i=0; i<totalEle; i++)
{
printf( "\n Enter element %d: ", (i+1) );
scanf("%d", &number[i]);
}
largest = find_largest(totalEle);
printf("\n Largest number is: %d", largest);
return 0;
}
int find_largest( int totalEle)
{
int largest = number[0];
for(int i=1; i<totalEle; i++)
{
if ( number[i] > largest )
largest = number[i];
}
return largest;
}
Meaning and Output:
Based on the code
provided, the program prompts for the number of elements, takes input for
an array, finds the largest value using a function, and prints it.
Example Output:
text
Enter total number of elements in the series:
5
Taking input to the array elements:
Enter element 1: 10
Enter element 2: 55
Enter element 3: 2
Enter element 4: 90
Enter element 5: 35
Largest number is: 90
·
Logic: The user enters 5 as the total elements.
The program then accepts five numbers, compares them within find_largest,
and outputs the maximum value (90 in this case).
This C program finds
the largest number in a user-defined series (up to 20 integers) using a
function. It takes input in main(), passes the total elements to find_largest(),
which iterates through the array to identify the maximum value.
Key Details:
·
Array
Size: number[20] restricts input
to a maximum of 20 elements.
·
Logic: find_largest initializes largest with the first
element and updates it if a larger element is found.
·
Functionality: It properly takes input, calls the
function, and prints the result.
·
Limitations: The code does not check if totalEle exceeds 20,
which could cause a buffer overflow.
c
#include<stdio.h>
int
find_largest (int);
int
number[20]; //
Array to store elements
int
main()
{
int totalEle, largest = 0;
printf("\n Enter total number of
elements in the series: ");
scanf("%d", &totalEle);
printf("\n Taking input to the array
elements: ");
for(int
i=0; i<totalEle; i++)
{
printf( "\n
Enter element %d: ", (i+1) );
scanf("%d",
&number[i]);
}
largest = find_largest(totalEle); // Call
function to find max
printf("\n Largest number is: %d",
largest);
return 0;
}
int
find_largest( int totalEle)
{
int largest = number[0]; // Assume first
is largest
for(int
i=1; i<totalEle; i++)
{
if (
number[i] > largest )
largest = number[i]; // Update largest
}
return largest;
}
Example 7.5: A C program for finding the digits of a number
using function.
Answer:
#include<stdio.h>
void find_digit(int number)
{
int temp = number, digit = 0;
while(temp > 0)
{
digit = temp % 10;
printf("\n Extracted digit is %d", digit);
temp = temp / 10;
}
}
int main()
{
int number;
printf("Enter the integer: ");
scanf("%d", &number);
find_digit(number);
return 0;
}
Meaning and Output
The program extracts
digits of an integer in reverse order. For input 123, the output is:
Enter the integer: 123
Extracted digit is 3
Extracted digit is 2
Extracted digit is 1
Explanation: The find_digit function uses temp % 10 to get the last digit and temp / 10 to remove it, repeating until 0
This C program defines
a function find_digit that takes an integer, uses a while loop with modulus (% 10) and division (/ 10) operators to isolate each digit, and prints them in reverse
order. The main function prompts the user for an integer
input, calls find_digit, and displays the extracted digits one by
one.
Key
Components:
·
find_digit Function: Extracts digits by taking temp % 10 (last digit) and reduces the number
using temp
/ 10.
·
Loop
Condition: Continues until temp becomes 0, meaning all digits are
processed.
·
Limitations: This code only works for positive
integers; inputting 0 or negative
numbers will result in no output or incorrect behavior.
Example Output:
If the input is 123, the output will be:
text
Extracted digit is 3
Extracted digit is 2
Extracted digit is 1
Example 7.6: A C program for storing the digits of a number in
an array using function.
Answer:
#include<stdio.h>
int digits[10];
int find_digit ( int number )
{
int temp = number, digit = 0, index = 0;
while ( temp > 0 )
{
digit = temp % 10;
printf ( "\n Extracted digit is %d", digit );
digits[index] = digit;
index = index + 1;
temp = temp / 10;
}
return (index-1);
}
int main()
{
int number, lastIndex;
printf ( "Enter the integer: " );
scanf ( "%d", &number );
lastIndex = find_digit ( number );
printf ( "\n Array elements are: \n" );
for ( int i=0; i < = lastIndex; i++ )
printf ("%d ", digits[i] );
return 0;
}
Meaning & Output:
It looks like you've written a C
program to extract the digits of an integer and store them in an array.
However, there is a small issue in the loop where you're printing the array
elements:
```c
for ( int i=0; i < =
lastIndex; i++ )
```
The space between `<` and `=`
is a typo. It should be `<=` instead of `< =`. Here's the corrected
version of the code:
```c
#include<stdio.h>
int digits[10]; // Array to store digits
int find_digit(int number)
{
int temp = number, digit = 0, index = 0;
while (temp > 0)
{
digit = temp % 10;
printf("\n Extracted digit is
%d", digit);
digits[index] = digit;
index = index + 1;
temp = temp / 10;
}
return (index - 1); // Return the index of the last digit
}
int main()
{
int number, lastIndex;
printf("Enter the integer: ");
scanf("%d", &number);
lastIndex = find_digit(number);
printf("\nArray elements
are:\n");
for (int i = 0; i <= lastIndex;
i++) // Fixed the typo here
{
printf("%d ", digits[i]);
}
return 0;
}
```
### Explanation:
1. **find_digit function**:
* Extracts the digits of the input integer `number` and stores them in
the `digits` array.
* It uses the modulus operator `%` to extract each digit and the
division operator `/` to reduce the number by removing the last digit.
* It returns the index of the last extracted digit, which will be used
to print the digits in the main function.
2. **Main function**:
* Reads an integer from the user.
* Calls the `find_digit` function to extract the digits.
* Prints the digits in the array.
### Sample Output:
```
Enter the integer: 12345
Extracted digit is 5
Extracted digit is 4
Extracted digit is 3
Extracted digit is 2
Extracted digit is 1
Array elements are:
5 4 3 2 1
```
Let me know if you'd like further
explanations or adjustments!
Example 7.7: A C program for displaying the digits of a number
in correct order.
Answer:
#include<stdio.h>
int digits[10];
int find_digit ( int number )
{
int temp = number, digit = 0, index = 0;
while ( temp > 0 )
{
digit = temp % 10;
printf ( "\n Extracted digit is %d", digit );
digits[index] = digit;
index = index + 1;
temp = temp / 10;
}
return (index-1);
}
void display_digits(int lastIndex)
{
printf("\n Array elements are: \n");
for ( int i = lastIndex; i >= 0; i-- )
printf ( "%d ", digits[i] );
}
int main()
{
int number, lastIndex;
printf ( "Enter the integer: " );
scanf ( "%d", &number );
lastIndex = find_digit ( number );
printf ( "\n Array elements are: \n" );
display_digits(lastIndex);
return 0;
}
Meaning
& Output
The
program extracts individual digits of an integer in reverse order using modulo
and division, stores them in an array, and then prints them in the correct
order. For input 123,
the output shows each extracted digit, then displays them in the original
order.
Example
Output (if input is 123):
Enter the integer: 123
Extracted digit is 3
Extracted digit is 2
Extracted digit is 1
Array elements are:
Array elements are:
1 2 3
Key
Behaviors:
·
Extracted digit: The digits are extracted from right to left (temp % 10).
·
Array storage: The digits are stored in reverse order in digits[].
·
Display: display_digits loops backward from lastIndex to 0, reversing the storage order to print them correctly.
·
Note: The program prints "Array elements are: " twice
because it is called in main and
again inside display_digits.
This C program prompts for an
integer, extracts its digits in reverse order using modulo/division, stores
them in a global array
digits[10],
and displays them in the original order. If 123 is entered, it prints "Extracted
digit is 3, 2, 1" and outputs "1 2 3", though it crashes with
large numbers (
>10is greater than 10
>10
digits) due to fixed array
size.
Program Analysis
- find_digit(int number): Extracts digits from right to
left using temp % 10, stores them in digits[index],
and returns the lastIndex (total digits - 1).
- display_digits(int lastIndex): Prints the digits stored in
the array from lastIndex down to 0
to reverse them back to the original order.
- main(): Handles input, calls the
functions, and outputs the result.
- Limitation: The digits[10]
array limits input to 10 digits; larger numbers will cause a buffer
overflow. It also does not handle negative numbers (while (temp > 0)).
Example Output (Input: 456)
OUTPUT-2:
Enter the integer: 456
Extracted digit is 6
Extracted digit is 5
Extracted digit is 4
Array elements are:
Array elements are:
4 5 6
Example 7.8: A C program for counting the number of adult
persons.
Answer:
#include<stdio.h>
int age[20];
int personCount = 0;
void input()
{
printf ( "\n We are taking inputs in an array \n" );
printf ( "\n How many persons are there? " );
scanf ( "%d", &personCount);
for ( int i = 0; i < personCount; i++ )
{
printf ( "\n Enter age of person %d: ", (i+1) );
scanf ( "%d", &age[i] );
}
printf ( "\n Input taken \n" );
}
void findAdult()
{
int adultCount = 0;
for ( int i = 0; i < personCount; i++ )
{
if ( age[i] >= 18 )
{
printf( "\n Person %d is an adult ", (i+1) );
adultCount++;
}
else
{
printf( "\n Person %d is NOT an adult ", (i+1) );
}
}
printf("\n Total number of adult persons: %d",
adultCount);
}
int main()
{
input();
findAdult();
printf ("\n\n" );
return 0;
}
Meaning & Output
This C program calculates the number
of adults from a user-defined list of ages. It uses a global array
age[20] to store
up to 20 inputs, takes the personCount, iterates through the array to check if each age is
≥18is greater than or equal to 18
≥18
, and prints whether each person is
an adult, finally displaying the total count.
Key Code Components:
·
input() function: Prompts for the number of people (personCount) and populates the age array using a for loop.
·
findAdult() function: Iterates through the stored ages, comparing each to 18 to
classify them as adults or minors, updating adultCount.
·
main() function: Orchestrates the program flow by
calling input() and findAdult().
·
Limitation: The array is fixed at int age[20], meaning it cannot process more than 20
people.
Based on the code
provided, the program prompts for the number of people, takes their ages as
input, checks if each is 18 or older, and outputs the status of each person
followed by the total adult count.
Assuming an input of 3
people with ages 15, 20, and 18, the output is:
We are taking inputs in an array
How many persons are there? 3
Enter age of person 1: 15
Enter age of person 2: 20
Enter age of person 3: 18
Input taken
Person 1 is NOT an adult
Person 2 is an adult
Person 3 is an adult
Total number of adult persons: 2
Example 7.9:
A C program for finding the factorial of a number.
Answer:
#include<stdio.h>
int findFacotiral ( int number )
{
int factorial = 1;
while ( number > 0 )
{
factorial = factorial * number;
number = number - 1;
}
return factorial;
}
int main()
{
int number, factorial = 0;
printf ("\n Enter the number: " );
scanf ( "%d", &number );
factorial = findFacotiral ( number );
printf ( "\n Factorial of the number is: %d",
factorial );
return 0;
}
Meaning
& Output
The provided C code
calculates the factorial of an integer input by the user.
Here is the breakdown
of the program's execution and output:
Program Description
The code first prompts
the user to enter a number. This number is then passed to the findFacotiral function,
which iteratively calculates the factorial. Finally, the program prints the result.
Output
The output depends on
the input provided by the user at runtime.
Scenario 1: User enters a small
positive integer (e.g., 5)
If the user enters the
number 5 when prompted, the output will be:
text
Enter the number: 5
Factorial of the number is: 120
Scenario 2: User enters 0
If the user enters the
number 0, the while loop condition (number > 0)
is immediately false. The function will return the initial value of factorial, which is 1.
text
Enter the number: 0
Factorial of the number is: 1
Note on Integer Overflow
The int data type in C
has a limited range. The provided code will produce incorrect results (due
to integer overflow) for factorials larger than 12! (13! is larger
than the maximum value for a standard 32-bit signed integer).
For example, if the
user enters 13, the output will be a seemingly random or
negative number, not the mathematically correct 6,227,020,800.
The provided C code calculates the
factorial of an integer input by the user. When the program runs, it first
prompts the user for input and then displays the result after the user enters a
number.
Output Scenarios
The output will depend entirely on
the integer value the user types in when prompted:
|
User
Input (number) |
Program
Output |
|
5 |
Factorial of the number is: 120 |
|
6 |
Factorial of the number is: 720 |
|
10 |
Factorial of the number is: 3628800 |
|
0 |
Factorial of the number is: 1 |
Detailed Program Execution Flow
- Prompt: The program prints the message Enter the number:
to the console. (Note: The leading \n in the printf statement causes a newline to be printed before the
text, if the previous command left the cursor on the same line.)
- Input Wait: The program waits for the user to type an integer
(e.g., 5)
and press Enter.
- Calculation: The findFacotiral function is called with the user's number. It uses a while loop
to iteratively multiply all positive integers from the input number down
to 1.
- Result Display: The main function receives the calculated factorial and prints
the final output message.
Potential Issues
- Negative Numbers: The current code will enter an infinite loop if the
user enters a negative number (e.g., -5), as the condition number
> 0 will always be true. The code
needs modification to handle negative inputs correctly.
·
Large
Numbers: Due to the limitations of the int data type, this program can only correctly calculate
factorials up to 12! Or 13! (depending on the system’s int size). Any number
larger will result in an incorrect output due to integer overflow.
Example 7.10: A C program for finding the factorial of a number
using recursion.
Answer:
#include<stdio.h>
int findFacotiral ( int number )
{
if ( number = = 0 )
return 1;
else
return number * findFacotiral ( number - 1 );
}
int main()
{
int number, factorial = 0;
printf ("\n Enter the number: " );
scanf ( "%d", &number );
factorial = findFacotiral ( number );
printf ( "\n Factorial of the number is: %d",
factorial );
return 0;
}
CHECK & MEANING
& OUTPUT
#include
<stdio.h>
// Function
definition must be declared before main to be properly used
int
findFactorial(int number) {
if (number == 0) {
return 1;
} else {
// Recursive call
return number * findFactorial(number -
1);
}
}
int main() {
int number, factorial = 0;
// Removed the incorrect leading comma in
the string literal
printf("\nEnter the number: ");
// The scanf arguments must be correctly
formatted: "%d" is the format specifier
scanf("%d", &number);
// Call the corrected function name
factorial = findFactorial(number);
// Removed the incorrect leading comma in
the string literal
printf("\nFactorial of the number is:
%d\n", factorial);
return 0;
}
Corrections Made:
1.
Function
Name: The original
function name was findFacotiral;
it has been corrected to findFactorial for
proper use within the main function.
2.
printf Statements: The original printf calls used a comma before the string
literal (e.g., printf ( \n Enter the number: );), which is a syntax error. Commas are used to separate
arguments, but the string literal is the first argument. These commas were
removed.
3.
scanf Statement: The original scanf had incorrect formatting (scanf ( %d ,
&number );). It was corrected
to scanf("%d",
&number); to adhere to the
standard format specifier syntax.
4.
Braces
in if/else: While not strictly necessary for single-line statements,
braces {} were added around the if and else blocks to improve readability and maintainability.
5.
Function
Prototype: Added a function
prototype/definition above the main function so the compiler recognizes the function findFactorial before it is called.
Output of the Corrected Code
The output will depend
on the number entered by the user.
If the user
enters 5:
Enter the number: 5
Factorial of the number is: 120
If the user
enters 0:
Enter the number: 0
Factorial of the number is: 1
Exercise
1. What is a global variable in C? Why do we need such a variable?
Answer:
A global variable in C
is a variable declared outside of all functions, usually at the beginning
of the source file [1]. It has a global scope, meaning it is
accessible from any function within the program, across all source files if
declared properly [2, 3]. Global variables are stored in the data segment of
the program's memory [2].
Why We Need Global Variables
We need global
variables for several key reasons:
·
Sharing
Data Across Functions: The
primary reason is to share data among multiple functions without constantly
passing the variable as an argument to each function call. This is particularly
useful for data that many parts of the program need to access, such as
configuration settings or program state [1, 4].
·
Persistent
Data: Unlike local
variables whose values are lost when the function they are declared in exits
(unless declared static), global variables
maintain their value throughout the entire execution of the program [3].
·
Convenience: They offer a convenient way to manage
values that are constant throughout the program's lifecycle, such as a maximum
user limit or a system flag [4].
·
Inter-file
Communication: When a large
program is split across multiple source files, global variables provide a
mechanism for variables in one file to be accessed and modified by functions in
another file, using the extern keyword [2,
3].
While global variables
offer convenience, they can also make a program harder to debug and maintain
due to potential side effects and unintended modifications from different parts
of the code. Therefore, their use is generally recommended to be limited to
scenarios where global access is truly necessary [1, 4].
2. Write the syntax of a function declaration. The name of
the function is calculateAge().
The function accepts the current year and birth year of a
person. The function returns the age of the person.
Answer:
The syntax for declaring the calculateAge function
in C, which accepts the current year and birth year and returns the age, is as
follows:
int calculateAge(int currentYear, int birthYear);
Explanation of the syntax:
·
int: This is the return type,
specifying that the function will return an integer value (the calculated age).
·
calculateAge: This is the function name.
·
(int
currentYear, int birthYear):
These are the parameters (also called arguments), enclosed in
parentheses.
o
int currentYear: The first parameter is an integer
named currentYear.
o
int birthYear: The second parameter is an integer
named birthYear.
·
;: The semicolon at the end signifies that this
is a function declaration (or prototype), not the full
definition of the function's body.
Full Example (Declaration and
Definition):
Here is an example
showing the declaration and the subsequent definition of the function within a
complete C program:
#include <stdio.h>
// Function Declaration
int calculateAge(int currentYear, int
birthYear);
int main() {
int current, birth, result;
// 1. Ask user for the current year
printf("Enter the current year: ");
scanf("%d", ¤t);
// 2. Ask user for their birth year
printf("Enter your birth year: ");
scanf("%d", &birth);
// 3. Call the function and store the returned value
result = calculateAge(current, birth);
// 4. Display the result
printf("You are %d years old.\n", result);
return 0;
}
// Function Definition
int calculateAge(int currentYear, int
birthYear) {
return currentYear - birthYear;
}
Explanation of the above:
To take
input from a user in C, you use the scanf function. This requires you to declare
variables to store the user's data and then pass those variables as arguments
to your calculateAge
function.
Key
Additions Explained
- scanf("%d", &variable): This is the standard way to get keyboard input.
- %d
tells the compiler to look for an integer.
- The & (address-of operator) is crucial; it tells scanf
exactly where in the computer's memory to store the number you typed.
- printf:
We use this before scanf to act as a "prompt," so the user knows what
they are supposed to type.
- Variables:
We created current and birth to hold the data temporarily before sending it to our
function.
Output:
Enter the current year: 2026
Enter your birth year: 1990
You are 36 years old.
Explanation of the Output:
1.
Enter the current year: The program prompts for input.
2.
2026 (User input)
3.
Enter your birth year: The program prompts for input.
4.
1990 (User input)
5.
2026 - 1990 The calculateAge function performs the subtraction.
6.
You are 36 years old. The final formatted output.
3. Write the code segment for the function definition of the above function calculateAge().
Answer:
In C programming, the function definition is the actual block of code that
contains the logic. While the declaration (prototype) just tells the compiler
the function exists, the definition describes how it works.
The Code Segment
Here is the standalone
function definition for calculateAge():
C
int calculateAge(int currentYear, int birthYear) {
int age;
age = currentYear - birthYear;
return age;
}
Breakdown of the Definition
·
Return
Type (int): Specifies that the function will send back an integer value.
·
Parameters
(int currentYear, int
birthYear): These are the local variables that receive
the values passed from the main() function.
·
Function
Body { ... }: Everything inside the curly braces is the
logic that executes when the function is called.
·
The
Logic: It subtracts the birthYear from the currentYear
and uses the return keyword to send the result back to the
caller.
Note: You can also write this more concisely as return currentYear - birthYear; without creating the extra age variable inside the function.
Would you like me to
help you write a similar function that calculates how many years are left until
a specific retirement age?
4. What are different types of functions in C? Differentiate
among them.
Answer:
Functions in C are
primarily categorized into two main types: Library Functions and User-Defined
Functions. User-defined functions can be further classified based on
whether they use arguments and return values.
Primary Classification
|
Aspect |
Library Functions (Predefined) |
User-Defined Functions (UDFs) |
|
Definition |
Built-in functions, pre-written
and stored in C libraries. |
Functions written by the
programmer for specific tasks tailored to program needs. |
|
Usage |
Reused across programs by
including the relevant header file (e.g., #include <stdio.h>). |
Defined within the program's
source code; no special header file is required for their definition. |
|
Customization |
Cannot be changed by the user. |
Fully customizable; the user
defines the logic and behavior. |
|
Examples |
printf(), scanf(), sqrt(), strlen(). |
Functions like calculateSum() or checkPrime() created
by a developer for a specific program. |
Secondary Classification
(User-Defined Functions)
User-defined functions
are subcategorized based on how data is passed to them (arguments) and how
results are sent back to the calling function (return value).
·
Function
with No Arguments and No Return Value:
o Description: Neither receives data from the calling function nor sends a
result back. Communication is minimal or relies on global variables.
o Use Case: Often used for simple tasks like printing a message or a fixed
pattern to the console.
·
Function
with Arguments but No Return Value:
o Description: Receives input (arguments) from the calling function to
perform operations, but does not return a value (uses void return type). This is a one-way data
communication.
o Use Case: Performing actions that don't need to pass a result back, such
as updating variables via pointers, input validation, or displaying information
based on input.
·
Function
with No Arguments but a Return Value:
o Description: Does not accept any input from the calling function but
returns a single value after its task is complete.
o Use Case: Useful for operations that generate a value internally without
external input, such as generating a random number or getting system date/time.
·
Function
with Arguments and a Return Value:
o Description: Accepts arguments (input) and performs a task, then returns a
single value to the calling function. This allows for a two-way data
communication.
o Use Case: The most common type, used for performing calculations and
transformations on given input, such as calculating the area of a rectangle or
the factorial of a number.
5. Differentiate
between caller and callee functions. write a small C progarm and identify the
caller and callee function in it.
Answer:
In programming, the
fundamental difference between caller and callee functions lies in their relationship
during execution:
·
Caller
Function: This is the function
that initiates or "calls" another function to perform a specific
task. It pauses its own execution and transfers control to the callee.
·
Callee
Function: This is the function
that is "called" by the caller. It executes the tasks defined within
its body and, upon completion, typically returns control and sometimes a value
back to the caller function.
Essentially, one
initiates the interaction, and the other responds to and performs the requested
operation.
C Program Example
In the following C
program, main() is the caller function, and multiply() is the callee function.
#include <stdio.h>
// Definition of the callee function 'multiply'
int multiply(int a, int b) { // <--- This is the CALLEE function
int result = a * b;
return result; // Returns the result to the caller
}
// Definition of the caller function 'main'
int main() { // <--- This is the CALLER function
int x = 5;
int y = 3;
int product;
// The 'main' function calls 'multiply'
product = multiply(x, y); // <--- This line is the 'call' operation
printf("The product of %d and %d is: %d\n", x, y, product);
return 0;
}
Identification
·
Caller
Function: main()
o The line product = multiply(x, y); is where main initiates the call to multiply.
·
Callee
Function: multiply()
o This function receives the inputs a and b, performs the multiplication, and returns the final value
to main.
6. When do we call a function user-defined? Is printf() a
user-defined function? Justify.
Answer:
A function is
called user-defined when it is explicitly declared and defined
by the programmer within the source code of a specific program [1].
Key characteristics of
a user-defined function include:
·
Defined
by the programmer: The function's
purpose, logic, and implementation are created by the coder to perform a
specific task required by their program [1].
·
Contained
within the program scope:
The source code for the function is written as part of the overall project,
unlike built-in functions provided by the language or operating system
libraries [1].
·
Customizable: The user can modify the function's behavior,
name, parameters, and return type as needed for their specific application
[1].
The printf() function is not a
user-defined function. It is a standard library function provided by the C
programming language [1].
Justification:
·
printf() is part of
the Standard I/O Library (stdio.h) which comes with the C compiler [1].
·
Programmers do not
write the source code for printf(); they simply call (use)
it within their programs to display formatted output to the console [1].
·
Its implementation is
standardized and provided by the system, not created by the individual user for
that specific program [1]. The user only needs to include the appropriate
header file (e.g., #include <stdio.h>) to access it [1].
7. Can we have two functions with the same name but with
different numbers of parameters in a single C program? Write a simple C program
to justify your answer.
Answer:
No, the C programming
language does not support function overloading, meaning you
cannot have two functions with the same name, even if they have a different
number or type of parameters. An attempt to do so in the same scope will result
in a compilation error.
Justification Program
The following C
program demonstrates that defining two functions with the same name, display_message, but different numbers of parameters, causes
a compilation error.
#include <stdio.h>
// Function with one parameter
void display_message(char *message)
{
printf("Message: %s\n", message);
}
// Function with two parameters (This will cause a compilation error)
/*
void display_message(char *message, int num)
{
printf("Message: %s, Number: %d\n", message, num);
}
*/
int main()
{
char message[] = "Hello, world!";
// Calling the function with one parameter. This is fine.
display_message(message);
// If the second function were uncommented, a call like
// display_message(message, 10);
// would also be a problem as the compiler wouldn't know which one to pick
// if a single definition was present.
return 0;
}
Explanation:
When the second display_message function is uncommented and the code is
compiled with a C compiler (like GCC), the compiler will issue an error, such
as "redefinition of 'display_message'" or "conflicting types for
'display_message'". The C compiler uses only the function name to identify
the function at link time and does not perform "name mangling" based
on the parameters like a C++ compiler does.
Workarounds in C
While true function
overloading is not a feature of C, similar behavior can be achieved using
alternative approaches, such as:
·
Different
Function Names: The most
straightforward method is to use distinct names (e.g., display_message_one() and display_message_two()).
·
Variable
Arguments: Using the <stdarg.h> library allows a function to accept a
variable number of arguments, as the printf() function does.
·
_Generic
Selection (C11 standard):
This preprocessor macro feature allows the compiler to select a different
function based on the type of a single argument at compile time.
8. What are different components of a function? Show with a
complete C program.
Answer:
In programming, a
function is a self-contained block of code that performs a specific task. Think
of it as a "mini-program" within your main program that you can reuse
whenever needed.
To use a function
properly, you need to understand its four primary components.
1. The Four Components of a Function
·
Function Prototype (Declaration): This tells the
compiler about the function's name, return type, and parameters before it is
actually used. It usually goes at the top of the file.
·
Function Call: This is the statement used to execute the function. When a
program "calls" a function, the control shifts to that function’s
definition.
·
Function Header (Definition Start): This is the first
line of the actual function code. It must match the prototype's structure.
·
Function Body: The set of statements enclosed in curly braces {}
that define what the function actually does.
2. Anatomy of a Function Header
The header itself
consists of three vital parts:
1.
Return Type: The data type of the value the function sends back (e.g., int,
float, or void if it returns
nothing).
2.
Function Name: A unique identifier used to call the function.
3.
Parameters (Arguments): A list of variables (placeholders) that receive data passed
into the function.
3. Complete C Program Example
Here is a simple
program that calculates the area of a rectangle to demonstrate all these
components in action.
C
#include <stdio.h>
// 1. FUNCTION PROTOTYPE
// Tells the compiler: "There is a function named
'calculateArea' that returns an int"
int calculateArea(int length, int width);
int main() {
int l = 10, w = 5;
int area;
// 2. FUNCTION CALL
// Execution jumps from here to the function definition below
area =
calculateArea(l, w);
printf("The area of the rectangle is: %d\n", area);
return 0;
}
// 3. FUNCTION HEADER
// Matches the prototype: Return type (int), Name
(calculateArea), Parameters (length, width)
int calculateArea(int length, int width) {
// 4. FUNCTION BODY
// The actual logic of the function
int result = length *
width;
return result; // Returning the value back to the caller
}
Summary Table
|
Component |
Purpose |
Location |
|
Prototype |
Notifies the compiler of the
function's existence. |
Above main() |
|
Call |
Invokes/starts the function. |
Inside main() or another function |
|
Parameters |
Passes data into the
function. |
Inside parentheses () |
|
Return Value |
Sends a result back to the
caller. |
End of function body |
Would you like me to
explain the difference between Pass by Value and Pass by Reference using this same example?
9.
Define recursive function. Can we use a recursive function to solve all kinds
of problems?
Answer:
A recursive function is a function
that calls itself, either directly or indirectly, to solve a problem.
The
core idea behind recursion is to break a large, complex problem down into
smaller, more manageable sub-problems of the same type. This continues until
you reach a "base case"—a simple scenario that can be solved without
further recursion.
1.
The Two Essential Parts of Recursion
Every
recursive function must have two components to work correctly:
·
Base
Case: The condition
under which the function stops calling itself. Without this, the function would
call itself infinitely, eventually leading to a Stack Overflow
error.
·
Recursive
Step: The part where
the function calls itself with a modified (usually smaller) version of the
original problem, moving closer to the base case.
2.
Can we use recursion for all problems?
Technically, yes, most problems
that can be solved with loops (iteration) can also be solved with recursion.
However, in practical programming, recursion is not always the best
choice.
When Recursion is Great:
·
Problems
with a naturally recursive structure: Like calculating Factorials, Fibonacci sequences, or the Tower
of Hanoi.
·
Tree/Graph
Traversal: Searching
through file systems or hierarchical data is much cleaner with recursion.
·
Divide
and Conquer Algorithms:
Sorting methods like QuickSort or MergeSort rely heavily on recursion.
When Recursion is Bad:
·
Memory
Efficiency: Each
recursive call adds a new layer (frame) to the system's "stack"
memory. If the recursion is too deep, you will run out of memory.
·
Performance: Recursive functions often involve more
overhead (function calls, stack management) than simple loops, making them
slower for basic tasks.
·
Complexity: If not handled carefully, recursive
logic can become harder to debug and read than a standard for or while loop.
3.
Example: Factorial Calculation
Here
is a quick comparison of how recursion looks in code versus its mathematical
logic.
C
#include <stdio.h> int factorial(int n) { // BASE CASE if (n <= 1) { return 1; } // RECURSIVE STEP else { return n * factorial(n - 1); }} int main() { int num = 5; printf("Factorial of %d is %d", num, factorial(num)); return 0;}The output of the code is
Factorial of 5 is 120.
The provided C program defines a
function factorial that recursively calculates the factorial of an integer 𝑛
Code Execution
Step 1: Initialize variable and call
function
The main function initializes an integer variable num to 5. It then calls the factorial(5) function.
Step 2: Perform recursive calculation
The factorial function uses the recursive formula
n!=n×(n−1)!n exclamation mark equals
n cross open paren n minus 1 close paren exclamation mark
𝑛!=𝑛×(𝑛−1)!
with a base case
1!=11 exclamation mark equals 1
1!=1
. The calculation resolves as
follows:
5!=5×4×3×2×1=1205 exclamation mark
equals 5 cross 4 cross 3 cross 2 cross 1 equals 120
5!=5×4×3×2×1=120
Step 3: Print the result
The printf statement formats the output string using the values of num (5) and the returned factorial value (120).
Answer:
The program prints the string Factorial
of 5 is 120 to the console.
10. Consider
the below code and list all the syntax errors.
#include<stdio.h>
int
fun ( int x )
{
if
( x %2 == 0 )
return
1;
else
return
0;
}
int
main()
{
int
number;
printf
("\n Enter the number: " );
scanf
( "%d", &number );
int
x = fun ( );
return
0;
}
Answer:
In the code provided,
there is one primary syntax/compilation error that will prevent
the code from running, along with a few "best practice" observations.
1. Missing Argument in
Function Call (Critical Error)
The most significant
error is in the main function:
C
int x = fun ( );
The function fun is defined as int fun ( int x ),
meaning it requires one integer argument. Calling it without
passing the variable number will cause a compilation error (specifically,
"too few arguments to function").
Corrected line:
C
int x = fun(number);
2. Potential Issues
(Depending on Compiler Standards)
While the following
might not crash every compiler, they are technically incorrect according to
strict C standards:
·
Logic
regarding x vs number: Inside main, you declare int x. However, your
function parameter is also named x. While C allows this (it's called
"shadowing"), it is confusing. More importantly, the variable x in main is being assigned the
result of the function, but it is never used.
·
Whitespace
in %2: In the line if ( x
%2 == 0 ), it is syntactically
legal, but standard convention suggests a space: x % 2 == 0.
·
Return
Type of main: While return 0; is present, some
older C standards prefer int main(void) if no command-line arguments are being used.
Summary Table of
Errors
|
Location |
Code |
Error Type |
Reason |
|
main function |
fun ( ) |
Syntax / Semantic |
Function fun expects an int but received nothing. |
|
main function |
int x = ... |
Logical Warning |
Variable x is initialized but never used (Unused Variable). |
Here is the corrected
version of the program. I have fixed the function call error, addressed the
unused variable, and cleaned up the formatting for better readability.
C
#include <stdio.h>
// Function definition: checks if a number is even
int fun(int x)
{
if (x % 2 == 0)
return 1; // Returns 1 for True (Even)
else
return 0; // Returns 0 for False (Odd)
}
int main()
{
int number;
printf("\n Enter the number: ");
// Ensure the input is captured correctly
if (scanf("%d",
&number) != 1) {
printf("Invalid input. Please enter an integer.\n");
return 1;
}
// CORRECTED: Passed 'number' as an argument to 'fun'
int result = fun(number);
// Using the returned value to provide feedback to the user
if (result == 1) {
printf("The number %d is Even.\n", number);
} else {
printf("The number %d is Odd.\n", number);
}
return 0;
}
Key Improvements Made:
·
Fixed
Function Call: Changed fun() to fun(number). In C, if a function
is defined with a parameter, you must provide a matching argument when calling
it.
·
Renamed
Variable x: In main, I changed the variable name from x to result. This avoids
confusion with the x used as a parameter inside the fun function.
·
Added
Output Logic: I added an if-else statement in main so that the program
actually tells the user the result of the calculation.
·
Input
Validation: Added a small check
to ensure scanf actually receives a valid number, which
prevents the program from behaving unpredictably with text input.
How the "Fix" Works in Memory
When you call fun(number), the program creates
a "stack frame." It copies the value of number from main into the variable x in fun. The function
performs the math, returns the answer, and then that stack frame is destroyed,
returning control to main.
Would you like me to
explain how to rewrite the fun function using a more concise ternary operator to make the code shorter?
11.
Consider the code segment below and find out the output if the user enters 5
from the keyboard when asked for.
#include<stdio.h>
int
fun ( int x )
{
if
( x %2 == 0 )
return
1;
else
return
0;
}
int
main()
{
int
number;
printf
("\n Enter the number: " );
scanf
( "%d", &number );
int
x = fun ( number);
printf("%d",
x);
return
0;
}
Answer:
The output when the user
enters 5 will be 0
If the user enters 5 from the keyboard, the output of the program will be 0.
Step-by-Step Execution:
1.
Input: The scanf function assigns the value 5 to the variable number.
2.
Function
Call: The program calls fun(5).
3.
Conditional
Check: Inside the function fun, it evaluates the
condition:
o 5 (mod 2) = = 0
o Since 5 divided by 2 leaves a remainder of 1, the condition 1 = = 0 is False.
4.
Return
Value: Because the if condition failed, the
function executes the else block and returns 0.
5.
Output: Back in main, the variable x becomes 0, and printf("%d",
x) prints 0 to the screen.
Understanding the Logic
This specific function
acts as an Even/Odd checker.
·
It returns 1 (True) if the number is Even.
·
It returns 0 (False) if the number is Odd.
Since 5 is an odd
number, the result is 0.
Would you like me to
show you how to modify this code so it prints the words "Even" or
"Odd" instead of just 1 or 0?
12. Write a C program and define
a function square() that accepts a number as the parameter and returns the
square of that number as output.
Answer:
To create this
program, we will define a function that takes an integer as an input,
multiplies it by itself, and returns the result to the main() function.
C Program to Calculate Square
C
#include
<stdio.h>
// Function Prototype
int square(int num);
int main() {
int input, result;
printf("Enter a number to find its square:
");
scanf("%d", &input);
// Calling the function and storing the return
value in 'result'
result = square(input);
printf("The square of %d is: %d\n", input, result);
return 0;
}
// Function Definition
int square(int num) {
// The function returns the number multiplied
by itself
return (num * num);
}
How the Data Flows
In this program, the
data moves through the different components we discussed earlier:
1.
Parameter
Passing: When you call square(input),
the value of input is copied into the local variable num inside the function.
2.
Processing: The function calculates $num \times num$.
3.
Returning: The return keyword sends that product back to the main() function, where it is
assigned to the variable result.
Key Components Used:
·
Return
Type: int (because the square
of an integer is an integer).
·
Parameter: int
num (the number being
sent to the function).
·
Return
Statement: return (num * num); (this exits the function and provides the answer).
Would you like to see
how to modify this to use float or double so it can handle decimal numbers as well?
13. Write a C program and define
a function search() that searches an element in an array and returns the index
of the element.
Answer:
To solve this, we will
use a Linear Search algorithm. This approach involves a
function that loops through each element of the array and compares it to the
target value.
C Program: Searching for an Element
C
#include <stdio.h>
// Function Prototype
// Returns the index if found, or -1 if the element does not
exist
int search(int arr[], int size, int target);
int main() {
int my_array[] = {12, 45, 7, 19, 23, 56};
int n = sizeof(my_array) / sizeof(my_array[0]); // Calculate array size
int key, result;
printf("Enter the number you want to search for: ");
scanf("%d",
&key);
// Function Call
result =
search(my_array, n, key);
if (result != -1) {
printf("Element found at index: %d\n", result);
} else {
printf("Element not found in the array.\n");
}
return 0;
}
// Function Definition
int search(int arr[], int size, int target) {
for (int i = 0; i < size; i++) {
// Check if the current element matches the target
if (arr[i] == target) {
return i; // Return the current index and exit function
}
}
// If the loop finishes without returning, the element isn't
there
return -1;
}
How the Search Function Works
·
Parameters: The function takes three pieces of
information: the array itself (arr[]), the number of elements in it (size), and the value we
are looking for (target).
·
The
Loop: We use a for loop to visit every
index from 0 to size
- 1.
·
Early
Exit: As soon as arr[i] == target
is true, the return i; statement executes. This immediately stops
the function and sends the index back to main.
·
The
Sentinel Value (-1): If the loop completes
and nothing is found, we return -1. This is a common practice in programming
because -1 is not a valid array index, so it clearly
signals "Not Found."
Important Considerations
·
Array
Size: In C, when you pass
an array to a function, the function doesn't automatically know how big it is.
That is why we must pass the size as a separate parameter.
·
Efficiency: This function has a Time Complexity of O(n), meaning in the worst
case (if the item is at the very end or missing), it has to check every single
element.
Would you like me to
show you how to perform a Binary Search, which
is much faster but requires the array to be sorted first?
14.
Write a C program and define a recursive function to find the summation of
first N natural numbers.
Answer:
#include
<stdio.h>
/*
* Recursive function to calculate the
summation of the first N natural numbers.
*/
int
sum_natural_numbers(int n) {
// Base case: if n is 1, the sum is 1.
if (n == 1) {
return 1;
}
// Recursive step: return the current
number plus the sum of all previous numbers.
else {
return n + sum_natural_numbers(n - 1);
}
}
int
main() {
int N;
// Prompt the user for input
printf("Enter a positive integer N to
find the summation of the first N natural numbers: ");
// Read the input
if (scanf("%d", &N) != 1 || N
<= 0) {
printf("Invalid input. Please
enter a positive integer.\n");
return 1; // Exit with an error code
}
// Call the recursive function and store
the result
int total_sum = sum_natural_numbers(N);
// Print the result
printf("The summation of the first %d
natural numbers is: %d\n", N, total_sum);
return 0;
}
How the program works:
1.
sum_natural_numbers(int n) function:
·
Base
Case: The function
checks if n is equal to 1. If it is, the recursion
stops, and it returns 1. This is crucial to prevent infinite recursion.
·
Recursive
Step: If n is greater than 1, the function returns
the sum of the current n and the result
of calling itself with n - 1. This process repeats
until the base case (n == 1) is reached.
main() function:
·
It prompts the user to
enter a number N.
·
It validates the input
to ensure it's a positive integer.
·
It calls the sum_natural_numbers function with the provided N and prints the final calculated
sum.
15.
Write a C program and define a function add() that accepts three integers.
These integers indicate indices of an integer array. The function returns the
summation of the elements stored in those indices.
|
7 |
8 |
8 |
0 |
0 |
9 |
For
example, if we call the function add( 0, 2, 5), the function will return 24.
The output is formed by 7 + 8 + 9 because elements at indices 0, 2 and 5 are 7,
8 and 9 respectively.
Answer:
Here's a C
program that defines a function `add()` to accept three integers as indices of
an array and returns the summation of the elements stored at those indices.
### Code:
```c
#include
<stdio.h>
// Function
that returns the sum of elements at three indices in an array
int add(int
index1, int index2, int index3, int arr[]) {
return arr[index1] + arr[index2] +
arr[index3];
}
int main() {
// Declare and initialize the array
int arr[] = {7, 8, 8, 0, 0, 9};
// Declare variables for the indices
int index1, index2, index3;
// Prompt the user for indices
printf("Enter three indices: ");
scanf("%d %d %d", &index1,
&index2, &index3);
// Call the add() function and print the
result
int result = add(index1, index2, index3,
arr);
printf("The sum of the elements at
indices %d, %d, and %d is: %d\n", index1, index2, index3, result);
return 0;
}
```
###
Explanation:
1. **add()
function**:
* The function accepts three integer indices
(`index1`, `index2`, `index3`) and an array `arr[]`.
* It returns the sum of the elements at
those three indices in the array.
2. **Main
function**:
* Initializes the array `arr[]` with the
values `{7, 8, 8, 0, 0, 9}`.
* Asks the user to input three indices.
* Calls the `add()` function to get the sum
of the elements at the given indices and prints the result.
### Sample
Output:
```
Enter three
indices: 0 2 5
The sum of the
elements at indices 0, 2, and 5 is: 24
```
###
Explanation of Example:
For indices
`0`, `2`, and `5`:
* Element at
index `0` = 7
* Element at
index `2` = 8
* Element at
index `5` = 9
The sum = `7 +
8 + 9 = 24`.
Let me know
if you'd like to explore anything further!