Goto Statement in C

This article covers the “goto” statement in C programming. The article goes on to explain two approaches to using “goto” in C, one where the label is declared before the “goto” statement and the other where it is declared after. The article concludes by summarizing why “goto” statements are discouraged.

The “goto” statement in C is a type of jump statement that allows for a change in the normal flow of the program. The “goto” statement can skip over certain codes or repeat a block by returning to a previously labelled block.

In this article, we will understand the “goto” statement in C and discuss its syntax, usage, and applications through examples. 

Table of Content

• What is Goto Statement in C?
• Ways of Implementing Goto Statement in C
• Why must the Use of the Goto Statement be Avoided?

So, without further delay, let’s get started! 

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What is Goto Statement in C?

The “goto” statement in C is an example of a jump statement used to change the flow of execution from one block of code to another. It is referred to as an unconditional jump statement. While it can be used to create loops, its main purpose is to control the execution of a program. 

The “goto” statement can change the order in which instructions are executed, but it is generally discouraged due to its potential to decrease the readability and understandability of the code. Sometimes, it can also exit multiple loops instead of using multiple break conditions.

Syntax

The syntax for a “goto” statement in C is shown below

goto label;
...
...
label:
// Code to execute after the goto statement

The label is a unique identifier followed by a colon, and a statement is the code executed when the “goto” statement jumps to that label. 

The “goto” statement can be placed anywhere in the code and, when executed, will transfer control to the labelled statement.

Flowchart

As depicted in the flowchart, when the “goto” statement is encountered, the code’s control jumps to the specified label’s location.

If the label is defined below the “goto” statement, the statements between the “goto” statement and the label are skipped.

Alternatively, if the label is defined before the “goto” statement, the statements between the “goto” statement and the label are repeated instead of skipped.

This is illustrated in the image provided.

Ways of Implementing Goto Statement in C

There are two approaches to using “goto” statements in C. One is where the label is declared before the “goto” statement, and the other is where the label is declared after the “goto” statement.

In the first approach, flow control moves from a lower to an upper part of the code, while in the second approach, flow control moves from an upper to a lower part of the code, potentially skipping some lines in between.

Let’s examine both methods in more detail to gain a deeper understanding.

Approach 1: Transferring Control Down-to-top

In this approach, the label is declared above the call of the “goto” statement. We will demonstrate this more clearly through an example.

Here is a revised and well-defined syntax

#include <stdio.h>

int main() {
    // Example initial statement
    printf("Beginning of the program.\n");

    // Label definition
    label_name: 
        // Statements after the label
        printf("This is statement 2.\n");
        printf("This is statement 3.\n");

        // Example condition for the goto statement
        int condition = 1; // Example condition variable
        if (condition) {
            goto label_name;
        }

    return 0;
}

Let’s consider an example to demonstrate how this logic might be applied.

Output

1 2 3 4 5 6 7 8 9 10 

In this program, the label print_line is declared above the call of the “goto” statement. The program’s control is transferred from the lower to the upper part, thus repeating the statements between the “goto” statement and the label declaration.

Approach 2: Transferring Control Top-to-down

In this approach, the label is declared after the call of the “goto” statement. We will demonstrate this more clearly through an example.

Here is a revised and well-defined syntax

#include <stdio.h>

int main() {
    statement1;
    // ...

    if (condition)
        goto label_name;

    statement2;
    // ...

label_name:

    statement3;
    statement4;
    // ...

    return 0;
}

Let’s consider an example to demonstrate how this logic might be applied.

Output

3

In this program, we add one to the answer only if a is not divisible by b; else, we use the “goto” statement to go straight to the label print_line. Thus, in this way, the “goto” statement helps transfer the control from top to down in the code.

Why must the Use of the Goto Statement be Avoided?

The “goto” statement in C should be avoided because it can lead to unstructured and difficult-to-understand code. The flow of control in a program with “goto” statements can be confusing and hard to follow, making it difficult to maintain or modify the code in the future. 

Additionally, “goto” statements can lead to infinite loops, unexpected behaviour, and unexpected results. Using more structured control flow statements like for, while, or if-else instead of “goto” is recommended.

Thus, the “goto” statement in C is a jump statement that transfers control from one part of the code to another. It changes the normal flow of the program, allowing for greater control and customization of the execution sequence.

I hope this article helped you grasp “goto” statements in C. Explore our C articles to learn more about the language and consolidate your knowledge of the fundamentals.