Signed vs unsigned behavior on 8-bit MCU in Embedded C - Hands-On Comparison

Signed vs unsigned behavior on 8-bit MCU

📖 Scenario: You are working with an 8-bit microcontroller unit (MCU) that handles small numbers in registers. Understanding how signed and unsigned numbers behave is important for correct calculations and avoiding errors.

🎯 Goal: You will create two 8-bit variables: one signed and one unsigned. You will assign values to them, perform arithmetic, and observe how the MCU treats these numbers differently.

📋 What You'll Learn

Create an 8-bit signed variable called signed_val with the value -10.

Create an 8-bit unsigned variable called unsigned_val with the value 250.

Create a variable called result to store the sum of signed_val and unsigned_val.

Print the value of result as an integer.

💡 Why This Matters

🌍 Real World

Embedded systems often use 8-bit MCUs for small devices like sensors, toys, and simple controllers. Understanding signed vs unsigned helps avoid bugs in calculations.

💼 Career

Embedded software engineers must know how data types affect arithmetic and memory on MCUs to write reliable and efficient code.

1

Create signed and unsigned 8-bit variables

Create an 8-bit signed variable called signed_val and set it to -10. Also create an 8-bit unsigned variable called unsigned_val and set it to 250.

Embedded C

// Your code here

Need a hint?

Use int8_t for signed 8-bit and uint8_t for unsigned 8-bit variables.

2

Create a variable to store the sum

Create an int16_t variable called result to store the sum of signed_val and unsigned_val.

Embedded C

#include 
#include 

int main() {
    int8_t signed_val = -10;
    uint8_t unsigned_val = 250;
    // Create result variable here
    // Your code here
    return 0;
}

Need a hint?

Use int16_t to hold the sum because it can store values larger than 8 bits.

3

Calculate the sum of signed and unsigned values

Assign to result the sum of signed_val and unsigned_val using the expression signed_val + unsigned_val.

Embedded C

#include 
#include 

int main() {
    int8_t signed_val = -10;
    uint8_t unsigned_val = 250;
    int16_t result = 0;
    // Calculate sum here
    // Your code here
    return 0;
}

Need a hint?

Use the plus operator + to add the two variables and assign to result.

4

Print the result

Use printf to print the value of result as a signed integer with the format specifier %d.

Embedded C

#include 
#include 

int main() {
    int8_t signed_val = -10;
    uint8_t unsigned_val = 250;
    int16_t result = signed_val + unsigned_val;
    // Print result here
    // Your code here
    return 0;
}

Need a hint?

Use printf("%d\n", result); to print the integer value followed by a new line.