Volatile keyword and why it matters in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a volatile integer variable named flag.

Embedded C

volatile [1] flag;

Drag options to blanks, or click blank then click option'

Aint

Bfloat

Cchar

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using a floating-point type instead of an integer.

Forgetting to use the volatile keyword.

The volatile keyword tells the compiler that the variable flag can change unexpectedly, so it should not optimize access to it. Here, flag is an integer.

2fill in blank

medium

Complete the code to declare a pointer to a volatile unsigned char named ptr.

Embedded C

volatile [1] *ptr;

Drag options to blanks, or click blank then click option'

Aint

Bchar

Cunsigned char

Dfloat

Attempts:

3 left

💡 Hint

Common Mistakes

Placing volatile after the asterisk.

Using signed char instead of unsigned char.

The pointer ptr points to a volatile unsigned char. The volatile keyword applies to the data pointed to, not the pointer itself.

3fill in blank

hard

Fix the error in the code by completing the declaration of a pointer to a volatile int named p.

Embedded C

[1] int *p;

Drag options to blanks, or click blank then click option'

Aint volatile

Bvolatile int

Cint

Dvolatile

Attempts:

3 left

💡 Hint

Common Mistakes

Writing int volatile *p; which is valid but not the expected style here.

Omitting the volatile keyword.

The keyword volatile before int means the pointer points to a volatile int. Writing volatile int *p; is correct. Here, the blank is for the keyword volatile.

4fill in blank

hard

Fill both blanks to complete the code that declares a pointer to a volatile int named vp.

Embedded C

[1] [2] *vp;

Drag options to blanks, or click blank then click option'

Avolatile

Bint

Cvolatile int

Dint volatile

Attempts:

3 left

💡 Hint

Common Mistakes

Putting volatile int together in one blank (not allowed here).

Swapping the order of volatile and int.

The correct declaration is volatile int *vp; which means vp points to a volatile int. The first blank is the keyword volatile, the second blank is the type int.

5fill in blank

hard

Fill all three blanks to complete the code that declares a pointer to a volatile unsigned int named vup.

Embedded C

[1] [2] [3] *vup;

Drag options to blanks, or click blank then click option'

Avolatile

Bunsigned

Cint

Dsigned

Attempts:

3 left

💡 Hint

Common Mistakes

Using signed instead of unsigned.

Omitting the volatile keyword.

The declaration volatile unsigned int *vup; means vup points to a volatile unsigned int. The blanks are filled with volatile, unsigned, and int respectively.