Basic data types - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of integer and float operations

What is the output of this C code snippet?

C

#include <stdio.h>
int main() {
    int a = 5;
    float b = 2.0;
    printf("%f", a / b);
    return 0;
}

A 2

B 2.000000

C 2.500000

D 0.000000

💡 Hint

Remember that dividing an int by a float results in a float.

The integer 'a' is promoted to float during division, so 5 / 2.0 equals 2.5, printed as 2.500000.

❓ Predict Output

intermediate

Size of data types

What will this program print?

C

#include <stdio.h>
int main() {
    printf("%zu", sizeof(char) + sizeof(int));
    return 0;
}

A 4

B 6

C 8

D 5

💡 Hint

On most systems, char is 1 byte and int is 4 bytes.

sizeof(char) is 1 byte, sizeof(int) is usually 4 bytes, so total is 5 bytes. But on 64-bit systems, int is 4 bytes, so sum is 5 bytes. However, the output is 5, not 8. This means option D is incorrect. We must check carefully.

❓ Predict Output

advanced

Unsigned integer overflow behavior

What is the output of this code?

C

#include <stdio.h>
int main() {
    unsigned int x = 0;
    x = x - 1;
    printf("%u", x);
    return 0;
}

A Compilation error

B 4294967295

C -1

D 0

💡 Hint

Unsigned integers wrap around on underflow.

Subtracting 1 from 0 in unsigned int wraps to the maximum unsigned int value, which is 4294967295 on 32-bit systems.

❓ Predict Output

advanced

Character and integer conversion

What does this program print?

C

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

A B 66

B A 65

C C 67

D Compilation error

💡 Hint

Characters are stored as numbers internally.

'A' has ASCII code 65, adding 1 gives 66 which is 'B'. So it prints 'B 66'.

🧠 Conceptual

expert

Behavior of signed integer overflow

What happens when a signed int variable in C overflows?

A It causes undefined behavior according to the C standard.

B It clamps to the maximum or minimum int value.

C It wraps around like unsigned int, producing a defined value.

D It triggers a runtime error automatically.

💡 Hint

Signed integer overflow is not defined by the C standard.

Signed integer overflow in C is undefined behavior, meaning the program may behave unpredictably.

Practice

1. Which C data type is used to store whole numbers without decimals?

easy

A. int

B. float

C. char

D. bool

Solution

1. Step 1: Understand data types for numbers

   Whole numbers without decimals are stored using the int type in C.

2. Step 2: Identify correct type for whole numbers

   float stores decimals, char stores characters, and bool stores true/false values.

3. Final Answer:

   int -> Option A

4. Quick Check:

   Whole numbers = int [OK]

Hint: Whole numbers use int type in C [OK]

Common Mistakes:

• Confusing float with int for whole numbers
• Using char for numbers
• Thinking bool stores numbers

2. Which of the following is the correct way to declare a variable of type float in C?

easy

A. int number = 3.14;

B. char number = 3.14;

C. float number = 3.14;

D. bool number = 3.14;

Solution

1. Step 1: Check variable declaration syntax

   In C, to declare a float variable, use the keyword float followed by the variable name and value.

2. Step 2: Match type with value

   Assigning 3.14 (a decimal) to a float variable is correct. Other types like int, char, or bool cannot hold decimal values properly.

3. Final Answer:

   float number = 3.14; -> Option C

4. Quick Check:

   Decimal numbers use float type [OK]

Hint: Use float keyword for decimal numbers [OK]

Common Mistakes:

• Using int for decimal values
• Assigning decimal to char
• Using bool for numbers

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

char letter = 'A';
int number = 5;
float decimal = 3.5;
printf("%c %d %.1f", letter, number, decimal);

medium

A. A 5 3

B. 65 5 3.5

C. A 5 3.50

D. A 5 3.5

Solution

1. Step 1: Understand format specifiers

   %c prints a character, %d prints an integer, and %.1f prints a float with one decimal place.

2. Step 2: Match variables to specifiers

   letter = 'A' prints 'A', number = 5 prints 5, and decimal = 3.5 prints 3.5 with one decimal.

3. Final Answer:

   A 5 3.5 -> Option D

4. Quick Check:

   Format specifiers match output [OK]

Hint: Match %c, %d, %.1f to char, int, float [OK]

Common Mistakes:

• Printing char as int (shows ASCII code)
• Ignoring decimal precision
• Confusing format specifiers

4. Identify the error in this C code snippet:

bool flag = 1;
char letter = "B";
int count = 10;

medium

A. char should use single quotes for characters

B. bool cannot be assigned 1

C. int cannot be assigned 10

D. No errors, code is correct

Solution

1. Step 1: Check bool assignment

   Assigning 1 to bool is allowed since 1 means true in C.

2. Step 2: Check char assignment

   Characters must be in single quotes ('B'), not double quotes ("B") which are for strings.

3. Final Answer:

   char should use single quotes for characters -> Option A

4. Quick Check:

   char uses single quotes [OK]

Hint: Use single quotes for char, double for strings [OK]

Common Mistakes:

• Using double quotes for char
• Thinking bool can't be 1 or 0
• Confusing int assignments

5. You want to store a student's grade as a letter (A, B, C, etc.) and whether they passed (true/false). Which data types should you use in C?

hard

A. int for grade, float for pass status

B. char for grade, bool for pass status

C. float for grade, int for pass status

D. bool for grade, char for pass status

Solution

1. Step 1: Choose type for grade letter

   Grade letters like 'A' are single characters, so char is the right type.

2. Step 2: Choose type for pass status

   Pass/fail is a true/false value, so bool fits perfectly.

3. Final Answer:

   char for grade, bool for pass status -> Option B

4. Quick Check:

   Letter = char, true/false = bool [OK]

Hint: Use char for letters, bool for true/false [OK]

Common Mistakes:

• Using int or float for letter grades
• Using char for true/false values
• Mixing data types incorrectly