Type modifiers in C - Mini Project: Build & Apply

Understanding Type Modifiers in C

📖 Scenario: You are working on a simple program that stores and displays information about a product's quantity and price. You need to use type modifiers to make sure the variables use the right amount of memory and represent the values correctly.

🎯 Goal: Build a C program that declares variables using type modifiers unsigned and long, assigns values, and prints them correctly.

📋 What You'll Learn

Declare an unsigned int variable called quantity and assign it the value 150

Declare a long int variable called price and assign it the value 50000

Declare an unsigned long int variable called total_cost

Calculate total_cost as quantity multiplied by price

Print the values of quantity, price, and total_cost using printf

💡 Why This Matters

🌍 Real World

Type modifiers help programmers use memory efficiently and avoid errors when working with numbers that have different ranges, such as quantities that cannot be negative or very large prices.

💼 Career

Understanding type modifiers is important for writing safe and efficient C programs, especially in embedded systems, systems programming, and performance-critical applications.

1

Declare variables with type modifiers

Declare an unsigned int variable called quantity and assign it the value 150. Also declare a long int variable called price and assign it the value 50000.

C

#include 

int main() {

    // Declare unsigned int quantity = 150
    // Declare long int price = 50000

    return 0;
}

Hint

Use unsigned int quantity = 150; and long int price = 50000; inside main().

2

Declare total_cost variable

Declare an unsigned long int variable called total_cost inside main() to store the total cost.

C

#include 

int main() {
    unsigned int quantity = 150;
    long int price = 50000;

    // Declare unsigned long int total_cost

    return 0;
}

Hint

Use unsigned long int total_cost; to declare the variable.

3

Calculate total_cost

Calculate the total cost by multiplying quantity and price, and assign the result to total_cost.

C

#include 

int main() {
    unsigned int quantity = 150;
    long int price = 50000;
    unsigned long int total_cost;

    // Calculate total_cost = quantity * price

    return 0;
}

Hint

Use total_cost = quantity * price; to calculate the total cost.

4

Print the values

Use printf to print the values of quantity, price, and total_cost in this exact format:
Quantity: 150
Price: 50000
Total cost: 7500000

C

#include 

int main() {
    unsigned int quantity = 150;
    long int price = 50000;
    unsigned long int total_cost;

    total_cost = quantity * price;

    // Print quantity, price, and total_cost

    return 0;
}

Hint

Use printf("Quantity: %u\n", quantity);, printf("Price: %ld\n", price);, and printf("Total cost: %lu\n", total_cost);.

Practice

1. Which of the following type modifiers in C is used to store only non-negative values?

easy

A. short

B. signed

C. long

D. unsigned

Solution

1. Step 1: Understand the meaning of 'unsigned'

   The 'unsigned' modifier means the variable can only hold zero or positive values, no negatives.

2. Step 2: Compare with other modifiers

   'signed' allows negative and positive values, 'short' and 'long' change size but not sign.

3. Final Answer:

   unsigned -> Option D

4. Quick Check:

   unsigned = non-negative only [OK]

Hint: Unsigned means no negative numbers allowed [OK]

Common Mistakes:

• Confusing 'signed' with 'unsigned'
• Thinking 'short' affects sign
• Assuming 'long' means unsigned

2. Which of the following is the correct way to declare a variable as a long unsigned integer in C?

easy

A. unsigned long int var;

B. int long unsigned var;

C. int unsigned long var;

D. unsigned int long var;

Solution

1. Step 1: Recall correct order of type modifiers

   The standard order is 'unsigned long int' to declare a long unsigned integer.

2. Step 2: Check syntax correctness

   unsigned long int var; follows the correct order and syntax; others mix order incorrectly.

3. Final Answer:

   unsigned long int var; -> Option A

4. Quick Check:

   unsigned long int = correct order [OK]

Hint: Use 'unsigned long int' order for clarity [OK]

Common Mistakes:

• Mixing order of 'unsigned' and 'long'
• Placing 'int' before 'unsigned'
• Using invalid modifier order

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

unsigned short x = 65535;
unsigned short y = 1;
unsigned short z = x + y;
printf("%u", z);

medium

A. 0

B. 65536

C. 1

D. 65535

Solution

1. Step 1: Understand the range of unsigned short

   Unsigned short typically stores values from 0 to 65535 (16-bit).

2. Step 2: Calculate the sum and check overflow

   65535 + 1 = 65536, which exceeds max value, so it wraps around to 0.

3. Final Answer:

   0 -> Option A

4. Quick Check:

   Unsigned short overflow wraps to 0 [OK]

Hint: Unsigned short max is 65535; adding 1 wraps to 0 [OK]

Common Mistakes:

• Expecting 65536 as output (overflow ignored)
• Confusing signed and unsigned overflow
• Using wrong printf format specifier

4. Identify the error in this C declaration:

unsigned signed int num;

medium

A. Missing variable name

B. Should use 'long' instead of 'signed'

C. Cannot combine 'unsigned' and 'signed' modifiers

D. No error, valid declaration

Solution

1. Step 1: Understand modifier compatibility

   'unsigned' and 'signed' are opposite modifiers and cannot be combined together.

2. Step 2: Check declaration validity

   Combining both causes a syntax error; variable name is present, so no missing name error.

3. Final Answer:

   Cannot combine 'unsigned' and 'signed' modifiers -> Option C

4. Quick Check:

   unsigned + signed = invalid [OK]

Hint: Don't mix 'unsigned' and 'signed' together [OK]

Common Mistakes:

• Thinking both can be combined
• Ignoring opposite meanings
• Assuming 'signed' is default and can be added

5. You want to store a large positive number that fits in 64 bits but never needs to be negative. Which type modifier combination is best in C?

hard

A. short unsigned int

B. unsigned long long int

C. long int

D. signed long long int

Solution

1. Step 1: Identify size and sign requirements

   64 bits means 'long long' type; only positive means 'unsigned'.

2. Step 2: Match modifiers to requirements

   'unsigned long long int' fits large positive numbers without negatives.

3. Final Answer:

   unsigned long long int -> Option B

4. Quick Check:

   64-bit positive number = unsigned long long int [OK]

Hint: Use 'unsigned long long int' for large positive 64-bit numbers [OK]

Common Mistakes:

• Choosing signed type when negatives not needed
• Using 'short' which is too small
• Ignoring 'unsigned' for positive-only data