PPS SEMII

Posted on Apr 6, 2026 in Computers

1. Short note on String

A String is a one-dimensional array of characters terminated by a null(‘\0’). Each character in the array occupies one byte of memory, and the last character
must always be null(‘\0’). The termination character (‘\0’) is important in a string to identify where the string
ends. 

Syntax:

charstring_name[size];

char name[10]; [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] 

 name[10           D A    R    S   H   A   N \0 

Declaration and Initialisation

You can declare and initialize a string in multiple ways:

Method 1:

char name[10] = {'D','A','R','S','H','A','N','\0'}; (Manual null termination Method 2:
char name[10] = "DARSHAN"; (The \0 is automatically inserted at the end)

Reading Strings from User 1scanf()

Used for simple strings. It terminates input at the first whitespace (space, tab, or newline). Example:

–

scanf("%s", name);

Gets() / fgets()

Used to read a complete string, including spaces. gets() reads until a newline is encountered.
    ex :
– char name[10] = “Dhruv”;    
             printf(“Name: %s”, name);

2. Explain different methods to read and print a string.        ——  Methods to Read Strings 1. Using scanf()

This is the most basic method for reading input.

Behavior:

It reads characters until it encounters the first whitespace (space, tab, or newline).

Key Detail:

You do not need the address-of (&) operator because the string name itself represents the base address.

Example:

scanf("%s", name);

2. Using gets() This function is specifically designed to read character strings

Behavior:

Unlike scanf(), it does not stop at whitespaces. It continues reading until a newline (\n) or End of File (EOF) is reached.

Advantage:

Useful for reading full names or sentences that include spaces.

Example:

gets(name);

3. Using fgets()

This is a more secure alternative to gets() as it allows you to specify the maximum number of characters to read.

Syntax:

fgets(str, size, stdin);

Behavior:

It reads a string including spaces and is preferred for preventing buffer overflows.

• Explain following :strlen, strcpy, strncpy, strcat, strncat, strcmp, strncmp, strstr, strchr,strrchr

Methods to Print Strings

1. Using printf() The standard formatted output function

Format Specifier:

Uses %s to print the character array.

Example:

printf("Name = %s", name);

2. Using puts()

A simpler function dedicated to outputting strings.

Behavior:

It prints the string and automatically adds a newline character at the end.

Example:

puts(name);

For the examples below, assume: char s1[20] = "Their"; and char s2[20] = "There";

1. Length and Copying

-strlen(s1)

Returns the length of the string as an integer (excluding the null character). Example: strlen("Hello") returns 5.

-strcpy(s1, s2)

Copies the entire second string (s2) into the first string (s1). The original content of s1 is overwritten. Example: After strcpy(s1, s2), s1 becomes "There".          – 

Strncpy(s1, s2, n)

Copies only the first n characters of s2 into s1. Example: strncpy(s1, "Apple", 2) makes s1 start with "Ap".

2. Concatenation (Joining)

-strcat(s1, s2)

Appends (joins) string s2 to the end of string s1. Example: –strcat("Their", "There") results in "TheirThere".

-strncat(s1, s2, n)

Appends only the first n characters of s2 to the end of s1. Example: –strncat("Their", "There", 2) results in "TheirTh".

3. Comparison strcmp(s1, s2) Compares two strings character by character

Returns 0 if strings are identical.
Returns a negative value if s1 < s2. Returns a positive value if s1 > s2.

-strncmp(s1, s2, n)

Compares only the first n characters of both strings.Example: strncmp("Their", "There", 3) returns 0 because “The” matches “The”.

4. Searching

Strstr(s1, s2)

Searches for the first occurrence 

Of the entire string s2 inside s1

It returns a pointer to the start of the match. Example: strstr("Hello World", "World") returns a pointer to "World". 

Strchr(s1, c)

Finds the first occurrence of a single character c in string s1. Example: strchr("Their", 'i') returns a pointer starting at "ir".

Strrchr(s1, c)

Finds the last occurrence (reverse search) of character c in string s1. Example: strrchr("There", 'e') returns a pointer to the very last 'e'

5 What is the function? Why it is important

A function is a group of statements that perform a specific task. It divides a large program into smaller parts. A function is something like hiring a person to do a specific job for you.  Every C program can be thought of as a collection of these functions. Program execution in C language starts from the main function.

Why function ?

Avoids rewriting the same code over and over. Using functions it becomes easier to write programs and keep track of what they
doing.

7 . What is Function? Explain type of User Defined Functions. Explain any two in detail

Types of User-Defined Functions

While built-in functions (like print() or sqrt()) come pre-installed, User-Defined Functions (UDFs)
are created by you to meet specific needs. They are generally categorized based on how they handle inputs (arguments)
And outputs (return values)
:

1. No Argument and No Return Value:

   
   The function does its job and prints the result itself.
2. 
   

   With Arguments and No Return Value:

   You give the function data, but it doesn’t “hand” anything back to the main program.
3. 
   

   No Argument and With Return Value:

   The function calculates something internally and sends the result back.

4. With Arguments and With Return Value:

The most common type; you provide data, and the function processes it and returns a result.

Detailed Look at Two Types

1. Function with Arguments and No Return Value :- In this model, the “calling” function sends data (arguments) to the “called” function. The called function uses that data to act but doesn’t send a result back to the logic that triggered it.

• How it works:

  
  Useful for tasks like printing a specific message or updating a global variable.
• 
  

  Example:

  A function that takes a name as an input and prints a personalized greeting.

2. Function with Arguments and a Return Value :- This is the most “complete” form of a function. It acts like a calculator: you put numbers in, it does the math, and it hands you the final answer to use elsewhere in your code.

• How it works:

  
  The return keyword is used to send a value back to the caller. This value can then be stored in a variable or used in further calculations.
• 
  

  Example:

  A function that takes two numbers ($x$ and $y$), adds them, and returns the sum $s$ where:
  s = x + y

9 Explain nesting of functions

1. Function Call Within a Function

While C does not support defining a function inside another function (unlike some other languages), it heavily relies on nesting calls.
This means main() can call Function A, and Function A can then call Function B.

2. Algorithm & Logic

Start:

The program begins execution in main().

Outer Call:

main() reaches a point where it needs a specific task done and calls the “Outer Function.”

Inner Call:

Inside the “Outer Function,” the code reaches a line that calls the “Inner Function.”

Return Path:

The “Inner Function” finishes and returns control to the “Outer Function.”     The “Outer Function” finishes and returns control back to main().

3. Code Example

#include <stdio.H>
#include <string.H>
// Inner-most logic (Standard Library Function): 
strlen()
// Outer Function: Calculates double
 the length
Int getDoubleLength(char str[]) {
    Int length = strlen(str); 
    Return length * 2;
}
Void main() {
    Char myStr[20] = "Darshan";
    Int result;
    Result = getDoubleLength(myStr);
    Printf("The double length of %s is: %d", myStr, result);
}

4. Key Rules to Remember   -No Nested Definitions:

You cannot write void functionA() { void functionB() { ... } }. This will result in a compilation error.

Scope:

A function called inside another must be either defined above it or declared (prototyped) at the top of the file.

Stack Memory:

Each time a function is called (nested), a new “frame” is added to the stack. If you nest too many calls (like in infinite recursion), you may hit a Stack Overflow.

Difference Between Local Variable and Global Variable

Example ;-

Demonstrate GoTo statement with an example. 

Syntax of goto

The syntax consists of two parts: the goto keyword and a unique label ending with a colon (:).

• Forward Jump:

  
  

  goto label;
  ...
  Label:
  

• Backward Jump (Looping):

  
  

  label:
  ...
  Goto label;
  

Code Example: Multiplication Table

#include <stdio.H>

Int main() {
    Int num, i = 1;
Printf("Enter the number whose table you want to
                                   print? ");
    Scanf("%d", &num);

    // Defining the label
    Table:
        Printf("%d x %d = %d\n", num, i, num * i);
        I++;

    // Conditional jump back to the label
    If(i <= 10)
        Goto table;

    Return 0;
}

What is an array? Briefly explain the array.

Definition

An array is a fixed-size, sequential collection of elements of the same data type grouped under a single variable name. Instead of declaring 100 separate variables for 100 students’ roll numbers, you can declare one array to hold them all.

Key Characteristics

• Fixed Size:
  Once declared, the size of the array (the number of elements it can hold) remains constant.
• Same Data Type:
  All elements in the array must be of the same type (e.G., all integers, all floats, or all characters).
• Sequential Memory:
  Elements are stored in contiguous memory locations and are accessed using an index.
• Zero-Indexed:
  In languages like C, the array index always starts at 0. If an array has a size of 5, the indices range from 0 to 4.

Basic Syntax (C Programming)

To declare an array, you specify the data type, the name, and the size in square brackets: data-type variable-name[size];

Example: int mark[5]; // Declares an integer array that can hold 5 values

Common Operations

1. Initialization:
   Assigning values at the time of declaration, e.G., int mark[5] = {85, 75, 65, 55, 45};.
2. Accessing:
   Retrieving a value using its index, such as mark[0] to get the first element.
3. Traversing:
   Using a for loop to read or print every element in the array sequentially.