What is C - Practice Questions & Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary use of the C programming language?

Which of the following best describes the main purpose of the C programming language?

A A scripting language used for automating tasks.

B A high-level language mainly used for web development.

C A low-level language used for system programming and embedded systems.

D A language designed exclusively for database management.

💡 Hint

Think about what kind of programs need direct hardware access and efficiency.

C is a low-level language that provides control over hardware and memory, making it ideal for system programming and embedded systems.

❓ Predict Output

intermediate

Output of a simple C program

What is the output of the following C program?

C

#include <stdio.h>

int main() {
    int a = 5, b = 3;
    printf("%d\n", a + b);
    return 0;
}

A 8

B 53

C 0

D Error: invalid syntax

💡 Hint

Remember that the + operator adds numbers, not concatenates them.

The program adds 5 and 3, printing 8.

❓ Predict Output

advanced

What is the output of pointer manipulation?

What will this C program print?

C

#include <stdio.h>

int main() {
    int x = 10;
    int *p = &x;
    *p = 20;
    printf("%d\n", x);
    return 0;
}

A Compilation error

B Address of x

C 10

D 20

💡 Hint

Changing the value pointed to by p changes x.

The pointer p points to x, so *p = 20 changes x to 20.

🔧 Debug

advanced

Identify the error in this C code snippet

What error will this C code produce?

C

#include <stdio.h>

int main() {
    int arr[3] = {1, 2, 3};
    printf("%d\n", arr[3]);
    return 0;
}

A Undefined behavior (accessing out of bounds)

B Compilation error

C Prints 3

D Prints 0

💡 Hint

Array indices start at 0 and go up to size-1.

Accessing arr[3] is out of bounds and causes undefined behavior.

🧠 Conceptual

expert

Why is C considered a 'portable' language?

Which reason best explains why C is called a portable programming language?

A Because C code can run without any changes on all hardware architectures.

B Because C compilers exist for many platforms, allowing code to be recompiled easily.

C Because C programs do not use any hardware-specific features.

D Because C automatically translates code to machine language for any device.

💡 Hint

Think about how code moves between different computers.

C is portable because many compilers exist for different systems, so source code can be recompiled on each platform.

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