Fixed-width integers (uint8_t, uint16_t, uint32_t) in Embedded C - Step-by-Step Execution

Concept Flow - Fixed-width integers (uint8_t, uint16_t, uint32_t)

Start

↓

Choose integer type

↓

Assign value

↓

Check value fits in bits?

No→Overflow occurs

Yes↓

Use value in program

↓

End

This flow shows how fixed-width integers are chosen, assigned values, checked for size limits, and used safely in embedded C.

Execution Sample

Embedded C

uint8_t a = 255;
uint16_t b = 50000;
uint32_t c = 3000000000;

Assign maximum and large values to fixed-width unsigned integers of 8, 16, and 32 bits.

Execution Table

Step	Variable	Assigned Value	Fits in Bits?	Result
1	a (uint8_t)	255	Yes (0-255)	a = 255
2	b (uint16_t)	50000	Yes (0-65535)	b = 50000
3	c (uint32_t)	3000000000	Yes (0-4294967295)	c = 3000000000
4	a (uint8_t)	256	No (overflow)	Value wraps to 0
5	b (uint16_t)	70000	No (overflow)	Value wraps to 4464

💡 Execution stops after demonstrating valid assignments and overflow wrap-around behavior.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5
a	undefined	255	255	255	0	0
b	undefined	undefined	50000	50000	50000	4464
c	undefined	undefined	undefined	3000000000	3000000000	3000000000

Key Moments - 3 Insights

Why does assigning 256 to a uint8_t variable cause it to wrap to 0?

Because uint8_t can only hold values from 0 to 255 (8 bits). Assigning 256 exceeds this range, causing overflow and wrapping back to 0, as shown in step 4 of the execution_table.

How do we know if a value fits in a fixed-width integer type?

Check if the value is between 0 and the maximum for that type (e.g., 0-255 for uint8_t). Steps 1-3 show valid assignments where values fit within the bit limits.

What happens if a value is too large for uint16_t, like 70000?

It causes overflow and wraps around modulo 65536 (2^16). Step 5 shows 70000 wraps to 4464 because 70000 - 65536 = 4464.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'a' after step 4?

A 255

B 256

C 0

D Undefined

💡 Hint

Check the 'Result' column for step 4 where 'a' wraps due to overflow.

At which step does the variable 'b' first get assigned a value that does NOT fit in its type?

A Step 5

B Step 3

C Step 2

D Step 4

💡 Hint

Look for 'Fits in Bits?' column showing 'No' for 'b' in the execution_table.

If we assign 256 to a uint8_t variable, what would be the new value after wrapping?

A 1

B 0

C 255

D 256

💡 Hint

Refer to step 4 in execution_table where 256 assigned to uint8_t wraps to 0.

Concept Snapshot

Fixed-width integers store unsigned numbers with exact bit sizes.
uint8_t holds 0-255 (8 bits), uint16_t holds 0-65535 (16 bits), uint32_t holds 0-4294967295 (32 bits).
Assigning values outside these ranges causes overflow and wraps around modulo 2^bits.
Use these types in embedded C to control memory and ensure predictable behavior.

Full Transcript

This visual execution shows how fixed-width unsigned integers work in embedded C. We start by choosing the integer type (uint8_t, uint16_t, uint32_t) and assign values. Each type has a range based on its bit size. For example, uint8_t can hold values from 0 to 255. If we assign a value within this range, it stores correctly. If the value is too large, like 256 for uint8_t, it overflows and wraps around to 0. Similarly, uint16_t can hold up to 65535, but assigning 70000 causes wrap-around to 4464. This behavior is important to understand to avoid bugs in embedded programming. The execution table tracks each step, showing variable values and whether they fit in the type. The variable tracker summarizes how values change after each assignment. Key moments clarify common confusions about overflow and range checking. The quiz tests understanding of these concepts by referencing the execution steps. Remember, fixed-width integers help control memory and ensure your program behaves predictably on embedded devices.