goto Statement in C

The goto statement allows a program to jump directly to a labeled statement within the same function. It is mainly used for error handling or exiting deeply nested loops, but excessive use can make code difficult to read and maintain.

• Transfers program control to a specified label within the same function.
• Best used for error handling or breaking out of multiple nested loops; avoid unnecessary use.

#include <stdio.h>

int main() {
    int n = 0;  

    // If the number is zero, jump to
  	// jump_here label
    if (n == 0)
        goto jump_here;

    // This will be skipped
    printf("You entered: %d\n", n);

jump_here:
    printf("Exiting the program.\n");
    return 0;
}

Exiting the program.

Explanation

• If num is 0, the goto statement transfers control directly to the jump_here label, skipping the remaining statements.
• If num is non-zero, the program prints its value normally, demonstrating how goto changes the program's execution flow.

Syntax

goto label;

/* Statements */

label:

// Code to execute

Flowchart of goto

The goto statement allows for jumping to specific parts of a program and understanding its function is still valuable.

Examples of goto

Below are some examples of how to use a goto statement.

Check Even or Odd Number

#include <stdio.h>

int main() {
    int n = 26;
  
  	if (n % 2 == 0)
      
        // jump to even
        goto even;
    else
      
        // Jump to odd
        goto odd;

even:
    printf("%d is even", n);
  	return 0;
  	
odd:
    printf("%d is odd", n);
    return 0;
}

26 is even

Prints numbers from 1 to 10

#include <stdio.h>

int main(){
  
  	int n = 1;
  
// Label here
label:
    printf("%d ", n);
    n++;
    if (n <= 10)
      
      	// jumb back to the label
        goto label;
    return 0;
}

1 2 3 4 5 6 7 8 9 10

Explanation

• The program uses the goto statement to repeatedly jump back to the labeled statement, printing numbers from 1 to 10.
• After each iteration, n is incremented, and the loop continues until n becomes greater than 10, after which the program terminates.

Jumping Out of a Nested Loop

#include <stdio.h>

int main() {
    int i, j;

    for (i = 0; i < 5; i++) {
        for (j = 0; j < 5; j++) {
            if (i == 2 && j == 2) {
              
                // Break out of both loops
                goto exit_loops;  
            }
            printf("%d %d\n", i, j);
        }
    }

exit_loops:
    printf("Exited loop");
    return 0;
}

0 0
0 1
0 2
0 3
0 4
1 0
1 1
1 2
1 3
1 4
2 0
2 1
Exited loop

Explanation

• When i == 2 and j == 2, the goto statement immediately exits both the inner and outer loops by jumping to the specified label.
• This avoids using multiple break statements or extra flag variables, making it easier to exit nested loops.

Error Handling Using goto

#include <stdio.h>

int main() {
    int num = -1; 

    // Check if num is -1
    if (num == -1) {
      
        // Jump to error handling
        goto error;  
    }

    printf("Valid input: %d\n", num);
    return 0;

error:
    printf("Error: Invalid input detected.\n");
    return -1;
}

Error: Invalid input detected.

Explanation: goto is used to jump to the error label when an invalid input (e.g., -1) is entered. This allows for centralized error handling.