UP Board Solutions Class 10 Computer Science Chapter 7 Introduction to C

Introduction To 'C' Long Answer Type Questions (8 Marks)

Question 1. Explain the structure of a 'C' program with example.
Answer: Structure of 'C' Program: Before understanding the structure of a 'C' program you must know these important points:
• 'C' is a case sensitive language, it means all the keywords must be written in lower case.
• Key-words can't be used as a variable or function name.
• Every instruction should end with (;) sign.
• Preprocessor directives (required) should be there in the beginning.
• Function main () is must for a program.
Now to write a program in 'C' we need to follow these steps: Define preprocessor directives (include header files according to prototype functions, standard I/O library functions to be used).
• Open function main ()
• Assign data types and variables.
• Define the body of the function
• End the function main ()
Example
/* harsh.c: first example for students */
# include
void main ()
{
int a = 10, b = 15, с;
printf ("Hellow students \n");
c = a + b;
printf ("The sum of % d and % dis %d", a, b, c);
}
In the above example the first line /*harsh.c: first example for students */ is a comment and non-executable. Comments in 'C' begins with (/*) and ends with (*/).
Second-line #include is a preprocessor directive. The preprocessor processes the ‘C’ program before the compiler. Here stdio.h is a header file consists of standard I/O functions. A header file related to the functions used in program should be included at the beginning. The line void main() indicates “the beginning of the program". The compilation of the program starts from main () function. {, the symbol indicates the beginning of the main () function
The line int a = 10, b = 15, C; is for declaration of variables and data types.
Lines printf ("Hellow students \n”); C = a + b. printf (“The sum of % d and % d is % d”, a, b, c); are the body of the program. and symbol ‘}' indicates end of main () function.
In simple words: A C program has a specific structure including preprocessor directives, a main function, variable declarations, and the program body. It starts with header files, followed by the main() function which encloses the executable code, ensuring a systematic execution flow.

🎯 Exam Tip: Clearly defining each structural component of a C program and providing a simple, well-commented example can earn full marks in this type of question.

Question 2. What is looping? Write about the different statements used to erect loop in 'C'?
Answer: Looping Statements: A computer program is a set of statements, which is normally executed sequentially. But in most of the cases, it is necessary to repeat certain steps to meet a specific condition. This repetitive operation is done through a loop control structure. A loop is basically the execution of the sequence of statements repeatedly until a particular condition is true or false. In 'C' language following looping statements are used:
while Statements: The while loop repeats a statement or a set of statements until a certain condition is true. Syntax
while (condition)
{
statements
}
Here, the condition may be any expression having a non-zero value. The loop continues until the condition is true. When the condition fails, the program body attached with loop (statements), will not be executed.
Example: To print the first 20 natural numbers.
#include<stdio.h>
#include<conio.h>
void main ()
{
int a = 1;
while (a <= 20)
{
printf ("%d", a);
a++;
}
getch();
}
do-while statement: Working of this statement is similar to the working of while statement but in this, at least one time the attached loop (statements) is executed, no matter whether the condition is true or false. Synax:
do
{
statements
}
while (condition);
Example: To print first 10 odd numbers.
#include<stdio.h>
#include<conio.h>
void main ()
{
int a = 1;
do
{
printf ("%d", a);
a+ = 2;
{while (a <=19)};
}
for loop statement: The for loop is an ideal looping statement when we know how many times the loop will be executed. Syntax:
for (initialization; condition; counter)
{
statements
}
Here,
• Initialization is generally an assignment which is used to set the loop control variable, e.g., a = 0.
• Condition always tells the limit of the loop or determines when to exit the loop. e.g., a < 10
• Counter defines how the loop control variable will change each time the loop is repeated. This may be incremented or decremented. e.g., a++, a-
Example: To print your name 10 times.
#include<stdio.h>
#include<conio.h>
void main ()
{
int i;
char name [20];
clrscr();
printf ("Enter your name");
gets(name);
for (i = 1; i <= 10; i++)
puts (name);
}
getch();
}
In simple words: Looping in C allows a block of code to be executed repeatedly until a specific condition is met. 'while', 'do-while', and 'for' are the main looping statements, each suited for different scenarios of repetition control.

🎯 Exam Tip: When explaining looping, define what a loop is, list the three types (while, do-while, for), describe their syntax and working, and provide a small code example for each for clarity and higher scores.

Introduction To 'C' Short Answer Type Questions (4 Marks)

Question 1. Explain the character set in 'C'.
Answer: Character Set in 'C'. The set of characters that may appear in a legal 'C' program is called the character set for ‘C’. These include some graphics as well as non-graphic characters. The 'C' character set consists of upper case and lower case alphabets, special characters, digits and white spaces. The alphabets and digits together are called the alphanumeric characters. Alphabets A, B, C, ........., Y, Z. a, b, c, ........., y, z. ‘C' is case sensitive language, it means lower and upper case are different.
Digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
Special Characters
• , → Comma
• % → Percent sign
• . → Period
• ? → Question mark
• ; → Semicolon
• & → Ampersand
• : → Colon
• ^ → Caret
• # → Number sign (Hash)
• * → Asterisk
• ‘ → Apostrophe
• - → Minus sign
• " → Quotation mark
• + → Plus sign
• ! → Exclamation mark
• / → Slash
• | → Vertical bar
• \ → Backslash
• ~ → Tilde
• < → Opening angle bracket
• > → Closing angle bracket
• _ → Underscore
• $ → Dollar sign
• (→ Left parenthesis
• ) → Right parenthesis
• [ → Left bracket
• ] → Right bracket
• { → left brace
• } → Right brace
In simple words: The C character set defines all the valid characters that can be used to write a C program, including letters, digits, and special symbols, recognizing that C is case-sensitive.

🎯 Exam Tip: Listing various types of characters (alphabets, digits, special characters) and providing several examples for each category ensures a complete answer.

Question 2. What is a variable?
Answer: Variable: A variable is an entity that has a value and is known to the program by a name. A variable definition associates a memory location with the variable name. A variable can have only one value assigned to it at any given time during the execution of the program. Its value may change during the execution of the program. Example: a = 20, 5; b = 10; here, a and b are variables.
Variable names are identifiers used to name variables. They are symbolic names given to memory locations. A variable name consists of a sequence of letters and digits, the first character being a letter. The rules that apply to identifiers also apply to variable names.
Examples of valid variable names are: a → Class abcl → employee Stu-data → 12 MAX
Examples of invalid variable names are: a's → illegal character (') Stu data → blank space not allowed 2Max → first character should be a letter Classmarks → comma not allowed
In simple words: A variable in C is a named storage location in memory that holds a value, which can change during program execution. It acts as an identifier for data, adhering to specific naming rules.

🎯 Exam Tip: Define variables clearly, state their mutable nature, and provide examples of both valid and invalid variable names, along with reasons for invalidity, to demonstrate full understanding.

Question 3. WAP to input 10 numbers and print its sum.
Answer:
#include<stdio.h>
#include<conio.h>
void main ()
{
int N, SUM = 0, i;
clrscr();
for (i=1; i <=10; i++)
{
printf ("Enter a number”);
scanf ("%d", & N);
SUM = SUM + N;
}
printf (“\n The sum often numbers is % d”, SUM);
getch();
}
In simple words: This C program calculates the sum of ten numbers provided by the user, using a loop to repeatedly input numbers and accumulate their total.

🎯 Exam Tip: Ensure correct header files are included, loop logic is sound for input and summation, and output displays the final sum clearly. Pay attention to syntax for maximum marks.

Question 4. WAP to find the sum of following series:
Answer: Sum = \[ \frac { 1 }{ 1 } +\frac { 1 }{ 2 } +\frac { 1 }{ 3 } +..........+\frac { 1 }{ n } \]
#include<stdio.h>
#include<conio.h>
void main ()
{
int n, i;
float sum;
printf ("Enter the number of terms\n");
scanf("%. d", & n);
i = 1;.
do
{
sum = sum + 1 /i;
i = i + 1;
}
while (i <= n);
printf ("% f\ sum);
getch();
}
In simple words: This C program calculates the sum of the series \(1/1 + 1/2 + \dots + 1/n\) by taking 'n' as input and iteratively adding the reciprocal of each integer to a running total.

🎯 Exam Tip: For series calculations, ensure the loop iterates correctly and that the division operation handles floating-point values properly if the sum is expected to be a float. Pay attention to variable types and format specifiers.

Question 5. WAP to calculate factorial or any given number.
Answer:
#include<stdio.h>
#include<conio.h>
void main()
{
int n, i;
long int fact = 1;
clrscr();
printf(“\n Enter any number”);
scanf("%d", & n);
for (i=1; i <= n; i++)
{
fact = fact *i;
}
printf ("The factorial of % d is % 1d”, n, fact);
getch();
}
In simple words: This C program computes the factorial of a user-provided number by multiplying all integers from 1 up to that number using a `for` loop.

🎯 Exam Tip: For factorial programs, ensure the `fact` variable is initialized to 1, use an appropriate data type (like `long int`) to handle larger factorials, and the loop iterates correctly from 1 to the input number.

Question 6. WAP to generate the following series: 1 2 233344445 5 5 5 5
Answer:
#include<stdio.h>
#include<conio.h>
void main()
{
int i, j;
clrscr();
for (i=1; i <= 5; i ++)
{
for (j=1; j <= i; j++)
{
printf ("%d\t", i);
}
}
printf ("\n");
getch();
}
In simple words: This C program generates a specific number series using nested `for` loops, where the outer loop controls the number printed and the inner loop controls how many times each number is repeated.

🎯 Exam Tip: Nested loops are key for generating patterns and series. Ensure the outer loop controls the primary iteration and the inner loop controls the repetition or secondary pattern, with correct loop conditions and print statements.

Introduction To 'C' Very Short Answer Type Questions (2 Marks)

Question 1. From where the compilation of the program starts?
Answer: from main () function.
In simple words: In a C program, the execution always begins from the `main()` function, serving as the entry point for the compiler.

🎯 Exam Tip: Remember that `main()` is the universal entry point for C programs, a fundamental concept for understanding program execution flow.

Question 2. % operator returns what?
Answer: Remainder.
In simple words: The `%` operator in C, known as the modulo operator, computes and returns the remainder of an integer division.

🎯 Exam Tip: The modulo operator `%` is crucial for tasks like checking even/odd numbers or cyclically accessing elements; know its function well.

Question 3. Who developed 'C' language?
Answer: Dennis Ritchie and Ken Thompson.
In simple words: The C programming language was primarily developed by Dennis Ritchie, with contributions from Ken Thompson, at Bell Labs.

🎯 Exam Tip: Knowing the pioneers like Dennis Ritchie is important as it reflects understanding of the language's history and foundation.

Question 4. A loop within a loop is known as ..........
Answer: Nested loop.
In simple words: A nested loop refers to a programming construct where one loop is placed inside another loop, allowing for complex iterative patterns.

🎯 Exam Tip: Understanding nested loops is vital for tasks requiring multi-dimensional iteration, such as processing matrices or generating patterns, and is a common exam topic.

Question 5. Which data type consists of fractional values?
Answer: float.
In simple words: The `float` data type in C is used to store numbers that have decimal points, also known as fractional or real numbers.

🎯 Exam Tip: Differentiate between integer (`int`) and floating-point (`float`, `double`) data types, as choosing the correct type is fundamental for accurate calculations and memory management.

Introduction To 'C' Objective Type Questions (1 Marks)

Question 1. A variable name must start with:
(a) A number
(b) An alphabet
(c) $ symbol
(d) # sign
Answer: (b) An alphabet
In simple words: According to C programming rules, a variable name must always begin with an alphabet or an underscore, never a digit or special character.

🎯 Exam Tip: Memorize the rules for valid identifiers (variable names) in C; starting with an alphabet or underscore is a basic yet crucial rule frequently tested.

Question 2. % s is used for:
(a) Character data type
(b) Numeric data type
(c) String data type
(d) Float data type
Answer: (c) String data type
In simple words: In C, `"%s"` is a format specifier used in functions like `printf()` and `scanf()` to handle and display string data.

🎯 Exam Tip: Familiarize yourself with common format specifiers like `%d`, `%f`, `%c`, and `%s` as they are essential for input/output operations and often appear in objective questions.

Question 3. '!=' is a/an:
(a) Arithmetical operator
(b) Relational operator
(c) Logical operator
(d) Assigning operator
Answer: (b) Relational operator
In simple words: The `!=` symbol in C is a relational operator, which checks if two operands are not equal, returning true or false.

🎯 Exam Tip: Distinguish between different types of operators (arithmetic, relational, logical, assignment) as their correct identification is fundamental for writing conditional statements and expressions.

Question 4. Which header file is used for scanf () and printf ()?
(a) conio.h
(b) stdio.h
(c) math.h
(d) Both (a) and (b)
Answer: (d) Both (a) and (b)
In simple words: The `stdio.h` header file is essential for standard input/output functions like `scanf()` and `printf()`, while `conio.h` provides console I/O functions often used alongside.

🎯 Exam Tip: Understand the purpose of common header files; `stdio.h` is fundamental for basic I/O, `conio.h` for console-specific functions, and `math.h` for mathematical operations.

Question 5. Which of them is not a looping statement?
(a) for
(b) while
(c) if
(d) do-while
Answer: (c) if
In simple words: `if` is a conditional statement used for decision-making, executing a block of code once if a condition is true, whereas `for`, `while`, and `do-while` are looping statements that repeatedly execute code.

🎯 Exam Tip: Differentiate clearly between control flow statements: `if`/`else` for selection (one-time execution) and `for`/`while`/`do-while` for iteration (repeated execution).