What is C - Interactive Quiz & Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print "Hello, World!" in C.

C

#include <stdio.h>

int main() {
    [1]("Hello, World!\n");
    return 0;
}

Drag options to blanks, or click blank then click option'

Aecho

Bprint

Cprintf

Dcout

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'print' instead of 'printf'.

Using 'cout' which is from C++.

The printf function is used in C to print text to the screen.

2fill in blank

medium

Complete the code to declare an integer variable named 'age' in C.

C

[1] age = 25;

Drag options to blanks, or click blank then click option'

Avar

Bnum

Cinteger

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'var' which is not valid in C.

Using 'integer' which is not a C keyword.

In C, int is used to declare integer variables.

3fill in blank

hard

Fix the error in the code to correctly declare a character variable named 'letter'.

C

char [1] = 'A';

Drag options to blanks, or click blank then click option'

Aletter

B1letter

Cchar

Dlet

Attempts:

3 left

💡 Hint

Common Mistakes

Starting variable name with a digit.

Using reserved keywords as variable names.

Variable names cannot start with a number. 'letter' is a valid name.

4fill in blank

hard

Fill both blanks to create a for loop that counts from 0 to 4 in C.

C

for (int i = [1]; i [2] 5; i++) {
    printf("%d\n", i);
}

Drag options to blanks, or click blank then click option'

A0

B<

C<=

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<=' causes the loop to run one extra time.

Starting the loop at 1 instead of 0.

The loop starts at 0 and continues while i is less than 5.

5fill in blank

hard

Fill all three blanks to declare and initialize an array of 3 integers in C.

C

int [1][[2]] = [3];

Drag options to blanks, or click blank then click option'

Anumbers

B3

C{1, 2, 3}

Darray

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid variable names.

Not using curly braces to initialize the array.

This declares an integer array named 'numbers' with 3 elements initialized to 1, 2, and 3.

Practice

1. What is C primarily known as?

easy

A. An operating system

B. A type of database

C. A web design tool

D. A fast and basic programming language

Solution

1. Step 1: Understand the nature of C

   C is a programming language used to write software.

2. Step 2: Identify its key features

   C is known for being fast and basic, making it popular for many applications.

3. Final Answer:

   A fast and basic programming language -> Option D

4. Quick Check:

   C = fast, basic language [OK]

Hint: Remember C is a programming language, not a tool or system [OK]

Common Mistakes:

• Confusing C with a database
• Thinking C is for web design
• Mixing C with operating systems

2. Which of the following is the correct way to start a C program?

easy

A. void start() {}

B. int main() {}

C. function main() {}

D. begin() {}

Solution

1. Step 1: Recall C program entry point

   In C, the program starts execution from the main function.

2. Step 2: Identify correct syntax

   The correct syntax is int main() {} which returns an integer.

3. Final Answer:

   int main() {} -> Option B

4. Quick Check:

   Program starts at main() [OK]

Hint: Look for int main() as program start [OK]

Common Mistakes:

• Using void instead of int for main
• Using non-C syntax like function keyword
• Using undefined start or begin functions

3. What will be the output of this C program?

#include <stdio.h>
int main() {
    printf("Hello, C!\n");
    return 0;
}

medium

A. Hello, C!

B. Hello, C!\n

C. printf("Hello, C!\n");

D. Error: missing semicolon

Solution

1. Step 1: Understand printf output

   The printf function prints the string inside quotes to the screen.

2. Step 2: Interpret escape sequence

   The \n adds a new line but does not print literally.

3. Final Answer:

   Hello, C! -> Option A

4. Quick Check:

   printf prints string with newline [OK]

Hint: Remember \n means new line, not printed text [OK]

Common Mistakes:

• Thinking \n prints as text
• Confusing code with output
• Assuming syntax error without cause

4. Find the error in this C code:

#include <stdio.h>
int main() {
    printf("Welcome to C programming")
    return 0;
}

medium

A. main function should return void

B. Wrong header file included

C. Missing semicolon after printf statement

D. printf syntax is incorrect

Solution

1. Step 1: Check syntax of printf line

   The printf statement must end with a semicolon.

2. Step 2: Identify missing semicolon

   Here, the semicolon after printf(...) is missing causing a syntax error.

3. Final Answer:

   Missing semicolon after printf statement -> Option C

4. Quick Check:

   Semicolon missing after printf [OK]

Hint: Look for missing semicolons after statements [OK]

Common Mistakes:

• Thinking header file is wrong
• Assuming main returns void
• Believing printf syntax is wrong

5. You want to write a C program that prints numbers 1 to 3 using a for loop in main. Which code snippet correctly does this?

hard

A. #include <stdio.h>
int main() {
for(int i=1; i<=3; i++)
printf("%d ", i);
return 0;
}

B. #include <stdio.h>
int main() {
printf("1 2 3\n");
return 0;
}

C. #include <stdio.h>
void main() {
printf("1 2 3\n");
}

D. #include <stdio.h>
int main() {
print("1 2 3\n");
return 0;
}

Solution

1. Step 1: Check program structure and output

   #include <stdio.h> int main() { for(int i=1; i<=3; i++) printf("%d ", i); return 0; } uses a loop to print numbers 1 to 3 with correct syntax.

2. Step 2: Verify correctness of other options

   The hardcoded printf prints numbers but not using a loop; the void main version is not standard; the print instead of printf causes an error.

3. Final Answer:

   for(int i=1; i<=3; i++) printf("%d ", i); -> Option A

4. Quick Check:

   Loop with printf prints 1 2 3 [OK]

Hint: Use for loop with printf to print sequence [OK]

Common Mistakes:

• Using void main instead of int main
• Using print instead of printf
• Not using loop for multiple prints