Goto statement overview in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple goto jump

What is the output of this C program?

C

#include <stdio.h>

int main() {
    int x = 0;
    goto skip;
    x = 5;
skip:
    printf("%d", x);
    return 0;
}

A 0

B 5

C Compilation error

D Undefined behavior

💡 Hint

The goto skips the assignment to x.

The goto jumps over the line 'x = 5;', so x remains 0. The program prints 0.

❓ Predict Output

intermediate

Effect of goto inside a loop

What is the output of this C code?

C

#include <stdio.h>

int main() {
    int i = 0;
start:
    if (i >= 3) goto end;
    printf("%d ", i);
    i++;
    goto start;
end:
    return 0;
}

A 0 1 2

B Infinite loop

C 0 1 2 3

D Compilation error

💡 Hint

The goto creates a loop until i reaches 3.

The code prints 0, 1, 2 with spaces, then exits when i is 3.

🔧 Debug

advanced

Identify the error caused by goto

What error does this C code produce when compiled or run?

C

#include <stdio.h>

int main() {
    int x = 10;
    goto label;
    x = x + 5;
label:
    printf("%d", x);
    goto label;
    return 0;
}

A No error, prints 10 once

B Compilation error: label redefined

C Runtime error: segmentation fault

D Infinite loop at runtime

💡 Hint

The goto jumps back to the same label without exit.

The code jumps to 'label' and then jumps back to 'label' again, causing an infinite loop printing 10 repeatedly.

📝 Syntax

advanced

Which option causes a syntax error?

Which of these goto usages causes a syntax error in C?

A goto start;

B goto 123label;

C end_label: printf("Hi");

D goto end_label;

💡 Hint

Labels must start with a letter or underscore.

Label names cannot start with a digit. '123label' is invalid syntax.

🚀 Application

expert

How many times is the word printed?

How many times will the word "Hello" be printed by this C program?

C

#include <stdio.h>

int main() {
    int count = 0;
start:
    if (count == 3) goto end;
    printf("Hello\n");
    count++;
    goto start;
end:
    return 0;
}

A Infinite times

B 4

C 3

D 0

💡 Hint

The loop stops when count reaches 3.

The program prints "Hello" three times before jumping to end and stopping.

Practice

1. What does the goto statement do in C programming?

easy

A. It jumps to a labeled part of the code within the same function.

B. It creates a new function.

C. It declares a variable.

D. It ends the program immediately.

Solution

1. Step 1: Understand the purpose of goto

   The goto statement is used to jump to a specific label inside the same function.

2. Step 2: Compare with other options

   Other options describe unrelated actions like creating functions or ending programs, which goto does not do.

3. Final Answer:

   It jumps to a labeled part of the code within the same function. -> Option A

4. Quick Check:

   goto jumps to label [OK]

Hint: Remember: goto jumps only inside the same function [OK]

Common Mistakes:

• Thinking goto can jump between functions
• Confusing goto with function calls
• Believing goto ends the program

2. Which of the following is the correct syntax to use goto in C?

easy

A. goto: label_name;

B. goto(label_name);

C. goto label_name;

D. goto = label_name;

Solution

1. Step 1: Recall correct goto syntax

   The correct syntax is simply goto label_name; without parentheses or equals sign.

2. Step 2: Check other options for syntax errors

   The other options use invalid syntax: one with a colon after goto, one with parentheses, and one with an equals sign.

3. Final Answer:

   goto label_name; -> Option C

4. Quick Check:

   Correct syntax is goto label; [OK]

Hint: Use 'goto label;' without parentheses or equals [OK]

Common Mistakes:

• Adding parentheses after goto
• Using equals sign with goto
• Writing colon after goto

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

int main() {
    int x = 0;
    start:
    x++;
    if (x < 3) goto start;
    printf("%d", x);
    return 0;
}

medium

A. 3

B. 0

C. 1

D. Infinite loop

Solution

1. Step 1: Trace the loop with goto

   The label start is before x++. The code increments x, then checks if x < 3. If yes, it jumps back to start.

2. Step 2: Count increments until condition fails

   x starts at 0, increments to 1, 2, then 3. When x is 3, condition x < 3 is false, so it stops looping and prints 3.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Loop increments x to 3 before printing [OK]

Hint: Count increments until condition fails [OK]

Common Mistakes:

• Thinking it prints 0 or 1
• Assuming infinite loop without checking condition
• Confusing label position

4. Identify the error in this C code using goto:

int main() {
    goto end;
    printf("Hello");
    end:
    return 0;
}

medium

A. Cannot jump over variable declarations.

B. No error; code runs and prints nothing.

C. Label 'end' is not defined.

D. Syntax error in goto statement.

Solution

1. Step 1: Check label definition and usage

   The label end is defined after the goto statement, so jumping to it is valid.

2. Step 2: Analyze program flow

   The program jumps to end, skipping the printf. So it prints nothing and returns 0 without error.

3. Final Answer:

   No error; code runs and prints nothing. -> Option B

4. Quick Check:

   Jumping to label after goto is allowed [OK]

Hint: Jumping forward to label is allowed; no error [OK]

Common Mistakes:

• Thinking label must be before goto
• Expecting output when skipped
• Assuming syntax error in goto

5. How can goto be used to break out of nested loops in C? Choose the best example.

hard

A. Use goto to jump to a label inside the inner loop.

B. Use goto to jump to a label after both loops finish.

C. Use goto to restart the inner loop from the beginning.

D. Use goto inside inner loop to jump to a label outside both loops.

Solution

1. Step 1: Understand nested loops and breaking out

   Normally, break exits only one loop. To exit multiple loops, goto can jump to a label after all loops.

2. Step 2: Identify correct usage of goto

   Using goto inside the inner loop to jump outside both loops immediately breaks out of all loops.

3. Final Answer:

   Use goto inside inner loop to jump to a label outside both loops. -> Option D

4. Quick Check:

   Goto jumps out of nested loops [OK]

Hint: Use goto to jump outside nested loops for quick exit [OK]

Common Mistakes:

• Using goto to restart loops instead of exit
• Jumping to label inside loops only
• Thinking break exits all loops