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MODULE 6 · LESSON 6.2 · PRACTICE

Switch Case Interview Questions for Embedded C: Quiz and Code Challenges

57 questions: multiple choice, write-the-label blanks, a construct-matching table, true/false, 6 code challenges with real output and 12 detailed interview answers. Treat it as a model for switch case interview questions.

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Section 1: Multiple Choice Questions — switch, case, break and default

These switch case interview questions in multiple-choice form are typical of written screening tests. Click an answer; explanations always appear.

1. Which types may be used as the controlling expression of a switch?

A) float and doubleB) Integer types, including char and enumC) char arrays (strings)D) Any type

2. What must a case label be?

A) Any variableB) A string literalC) A unique integer constant expressionD) A function call

3. What happens when a case does not end with break?

A) Compile errorB) The switch repeatsC) Execution falls through into the next caseD) The default runs

4. What does break do inside a switch that is inside a for loop?

A) Ends the programB) Leaves the loopC) Skips one iterationD) Leaves the switch only

5. What does continue do inside a switch that is inside a for loop?

A) Falls to the next caseB) Leaves the switch and runs the code after itC) Compile errorD) Jumps to the next iteration of the loop

6. Where may the default label appear?

A) Only firstB) Only lastC) Not inside a switchD) Anywhere in the switch body

7. What happens if no case matches and there is no default?

A) Nothing in the switch runsB) Compile errorC) The first case runsD) Undefined behavior

8. Which flag makes GCC warn about unannotated fall-through?

A) -WunusedB) -Wall onlyC) -Wimplicit-fallthrough (in -Wextra)D) -O2

9. Why should a case body that declares a variable be in braces?

A) To limit the scope and avoid skipped initialisersB) Required by syntax alwaysC) To speed up the codeD) To allow break

10. Which case label is valid?

A) case 'A':B) case x: with int x = 3;C) case 1.5:D) case "A":

11. A dense switch with many cases is most likely compiled to:

A) A loopB) A chain of string comparesC) A function callD) A jump table (TBB/TBH on Cortex-M)

12. Which switch is best expressed with a lookup table instead?

A) Each case just returns a constant for the valueB) Each case calls different functionsC) Cases with fall-throughD) A state machine

13. Which MISRA C rule demands a default label?

A) Rule 8.1B) Rule 16.4C) Rule 1.1D) Rule 21.3

14. What is a case 1 ... 5: range?

A) C++ onlyB) Standard CC) A syntax error everywhereD) A GCC extension, not portable

15. Which statement about switch on an enum is true?

A) Enums cannot be usedB) GCC cannot check itC) With -Wall GCC warns about unhandled enumerators when there is no defaultD) Enums need casts

-Wswitch checks enumerator coverage.

Section 2: Write or Evaluate (Fill in the Blanks)

Type the exact C label or keyword for the first three items and a short value for the rest.

1. Write the label that matches the character A:

case 'A':

2. Write the statement that leaves a switch:

break;

3. Write the label that handles every unmatched value:

default:

4. switch (3) { case 3: x = 1; case 4: x += 2; break; case 5: x += 4; } gives x = (x starts at 0)

5. switch (9) { case 1: x = 5; break; } with x = 7 beforehand leaves x =

6. How many break statements are needed to stack labels case 1: case 2: case 3: over one body?

7. The number of default labels allowed in one switch is at most

8. The standard keyword to leave only the switch is

Section 3: Which Construct Fits?

Choose the best tool, as asked in switch case interview questions about design.

Task	Your answer	Result
Decode a one-byte UART command into twelve different actions	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case
Check whether a temperature is above 30 °C	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case
Map month numbers to day counts	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case
Map an index 0–4 to a port name string	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case
Protocol parser that remembers where it is between bytes	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case
Cases that build on each other (init levels)	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case
Choose the action by comparing two variables	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case
A case that needs a local variable	switchifswitch with grouped labelsconst lookup tableenum + switchdeliberate fall-throughif-elsebraces around the case

Section 4: True or False

Statements typical of switch case interview questions.

1. Every case in a switch must end with a break statement for the code to compile.

2. A switch can have the same case value twice if the bodies differ.

3. The expression in a switch is evaluated once.

4. switch (str) with case "ON": compares the string contents.

5. A return inside a case does the job of a break.

6. The order of case labels affects which one matches.

7. A switch can be used to implement a finite state machine.

8. const int k = 3; switch (x) { case k: ... } is valid C.

Section 5: Code Snippet Challenges

Trace each program on paper first; the real output follows. These challenges are the code-reading half of switch case interview questions.

Challenge 1 — Output?: Missing breaks

#include <stdio.h>
int main(void)
{
    int x = 2;
    switch (x)
    {
        case 1: printf(“one “);
        case 2: printf(“two “);
        case 3: printf(“three “);
        default: printf(“other “);
    }
    printf(“\n”);
    return 0;
}

What is printed for x = 2?

Output:

two three other

Execution enters at case 2 and falls through case 3 and default, printing all three words.

Challenge 2 — Output?: default in the middle

#include <stdio.h>
int main(void)
{
    int x = 7;
    switch (x)
    {
        default: printf(“D “);
        case 1: printf(“one “);
            break;
        case 2: printf(“two “);
    }
    printf(“\n”);
    return 0;
}

What is printed for x = 7?

Output:

D one

No case matches, so control goes to default, which prints D and then falls into case 1 until the break. The position of default does not change that.

Challenge 3 — Output?: break and continue in a loop

#include <stdio.h>
int main(void)
{
    int n = 0;
    for (int i = 0; i < 4; i++)
    {
        switch (i)
        {
            case 1: continue;
            case 2: break;
            default: n += 10;
        }
        n++;
    }
    printf(“%d\n”, n);
    return 0;
}

What is n at the end?

Output:

i = 0: default adds 10, then n++ gives 11. i = 1: continue skips n++. i = 2: break leaves the switch, n++ gives 12. i = 3: default adds 10 giving 22, n++ gives 23.

Challenge 4 — Find the bug: Two labels with the same value

#include <stdio.h>
int main(void)
{
    char c = 5;
    switch (c)
    {
        case 5:
            printf(“five\n”);
            break;
        case 4 + 1:
            printf(“also five\n”);
            break;
    }
    return 0;
}

Does this compile?

Compiler result:dup.c: In function ‘main’: dup.c:10:9: error: duplicate case value 10 | case 4 + 1: | ^~~~ dup.c:7:9: note: previously used here 7 | case 5: | ^~~~The constant expression 4 + 1 equals 5, so the label duplicates the first one: a compile error.

Challenge 5 — Find the bug: Declaration right after a label

#include <stdio.h>
int main(void)
{
    int a = 1;
    switch (a)
    {
        case 1:
            int t = 5;
            printf(“%d\n”, t);
            break;
        case 2:
            printf(“two\n”);
            break;
    }
    return 0;
}

What does GCC say about this switch?

Compiler result:decl.c: In function ‘main’: decl.c:8:13: warning: a label can only be part of a statement and a declaration is not a statement [-Wpedantic] 8 | int t = 5; | ^~~Before C23 a label must be followed by a statement. GCC accepts it as an extension in its default mode and warns under -pedantic (C11 mode shown); the portable and safe form is to wrap the case body in braces.

Challenge 6 — Output?: A shift turns a range into a value

#include <stdio.h>
int main(void)
{
    unsigned v = 7;
    switch (v >> 2)
    {
        case 0:  printf(“0..3\n”); break;
        case 1:  printf(“4..7\n”); break;
        default: printf(“8+\n”);   break;
    }
    return 0;
}

What is printed for v = 7?

Output:

4..7

7 >> 2 is 1, so the second case runs. The shift maps 0–3 to 0, 4–7 to 1 and everything larger to other values.

Section 6: Switch Case Interview Questions for Embedded C (with Detailed Answers)

Switch case interview questions test your knowledge of fall-through, constants, compilation and state-machine design. Click a question for a model answer.

Q1. What is the difference between switch and if-else?Basic+

Q2. What does default do and is it mandatory?Basic+

Q3. What is fall-through? When is it acceptable?Intermediate+

Q4. How is a switch implemented by the compiler?Intermediate+

Q5. Can you use a string in a switch? What do you do instead?Intermediate+

Q6. Why put braces around a case that defines variables?Intermediate+

Q7. Write a state machine for a debounced button using a switch.Intermediate+

Q8. When would you replace a switch with a function-pointer table?Advanced+

Q9. A switch on a state variable occasionally does nothing in the field. What could be happening?Advanced+

Q10. Why can switch (c) misbehave for bytes above 127?Advanced+

Q11. What are the MISRA C rules about switch statements?Advanced+

Q12. What is Duff’s device and why is it banned in MISRA code?Advanced+

Study Plan: Using Your Score on These Switch Case Interview Questions

Score	Meaning	Next step
90–100%	Excellent	Continue to Module 7: loops, starting with the for loop.
70–89%	Good	Redo Examples 3, 5 and 8 of this lesson.
Below 70%	Revise	Re-read theory sections 3, 4 and 6, then retake the quiz.

Habit to build: Compile with -Wall -Wextra and treat every fall-through warning as a bug until you have annotated it.

Module 6 complete!

Next up: Module 7, loops: for, while, do-while, break and continue.

« Previous LectureLesson 6.2 Examples: Switch Case in Embedded C Next Lecture »Module 7 Lesson 7.1 Theory: The for Loop in Embedded C

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Questions about this free C programming course, embedded C training or career guidance? Get in touch.

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Quiz- Switch Case Interview Questions for Embedded C: Quiz and Code Challenges-Free Embedded C Course in Hyderabad

Switch Case Interview Questions for Embedded C: Quiz and Code Challenges

Section 1: Multiple Choice Questions — switch, case, break and default

Section 2: Write or Evaluate (Fill in the Blanks)

Section 3: Which Construct Fits?

Section 4: True or False

Section 5: Code Snippet Challenges

Section 6: Switch Case Interview Questions for Embedded C (with Detailed Answers)

Study Plan: Using Your Score on These Switch Case Interview Questions

Module 6 complete!

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