Goto statement overview in C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the goto statement in C?

The goto statement in C is a way to jump directly to another part of the program marked by a label. It helps to change the flow of execution.

beginner

How do you define a label for goto in C?

A label is defined by writing an identifier followed by a colon, like label_name:. The goto statement can jump to this label.

intermediate

Why should goto be used carefully?

Using goto too much can make code hard to read and follow, like a messy map. It can cause bugs and confusion, so it is usually better to use loops and functions.

beginner

Can goto jump outside a function in C?

No, goto can only jump to labels within the same function. It cannot jump between different functions.

beginner

Example: What does this code do?

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

The code jumps over x = 5; and prints 0 because the goto skip; moves execution directly to the label skip:.

What does the goto statement do in C?

A Starts a new function

B Ends the program

C Jumps to a labeled part of the code

D Declares a variable

The goto statement jumps to a label inside the same function.

How do you mark a place to jump to with goto?

A With a function name

B With a label followed by a colon

C With a comment

D With a variable

Labels are identifiers followed by a colon, like label:.

Can goto jump to a label in another function?

A No, only within the same function

B Yes, anywhere in the program

C Only if the functions are nested

D Only if the label is global

goto works only inside the same function.

What is a common problem with using goto too much?

A It causes syntax errors

B It makes the program run slower

C It uses too much memory

D Code becomes hard to read and maintain

Excessive use of goto can make code confusing and messy.

Which of these is a correct label for goto?

A start:

B int start;

C goto start;

D label start

Labels are written as an identifier followed by a colon, like start:.

Explain how the goto statement works and when it should be used.

Think about how <code>goto</code> changes program flow and why it can be risky.

Describe a simple example where goto skips a part of the code.

Imagine skipping a step in a recipe using a shortcut.

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