Another common change to programming languages was the removal of the GOTO statement, which allowed the program execution to jump to an arbitrary point in the code (much like a choose-your-own adventure book will direct you to jump to a page). The GOTO came to be considered too primitive, and too easy for a programmer to misuse ¹.

While the GOTO statement is absent from most modern programming languages the actual functionality remains, abstracted into control-flow structures like conditionals, loops, and switch statements. This is the basis of structured programming, a paradigm adopted by all modern higher-order programming languages.

Each of these control-flow structures can be represented by careful use of GOTO statements (and, in fact the resulting assembly code from compiling these languages does just that). The benefit of using structured programming is it promotes “reliability, correctness, and organizational clarity” by clearly defining the circumstances and effects of code jumps ².

You probably aren’t very familiar with GOTO statements because the structured programming paradigm has become so dominant. Before we move on, let’s see how some familiar structured programming patterns were originally implemented using GOTOs:

Conditional (if statement)

In C#, you are probably used to writing if statements with a true branch:

int x = 4;
if(x < 5) 
{
  x = x * 2;
}
Console.WriteLine("The value is:" + x);

With GOTOs, it would look something like:

int x = 4;
if(x < 5) goto TrueBranch;

AfterElse:
  Console.WriteLine("The value is:" + x);
  Environment.Exit(0);

TrueBranch:
  x = x * 2;
  goto AfterElse

Conditional (if-else statement)

Similarly, a C# if statement with an else branch:

int x = 4;
if(x < 5) 
{
  x = x * 2;
}
else 
{
  x = 7;
}
Console.WriteLine("The value is:" + x);

And using GOTOs:

int x = 4;
if(x < 5) goto TrueBranch;
goto FalseBranch;

AfterElse:
  Console.WriteLine("The value is:" + x);
  Environment.Exit(0);

TrueBranch:
  x = x * 2;
  goto AfterElse;

FalseBranch: 
  x = 7;
  goto AfterElse;

Note that with the goto, we must tell the program to stop running explicitly with Environment.Exit(0) or it will continue on to execute the labeled code (we could also place the TrueBranch and FalseBranch before the main program, and use a goto to jump to the main program).

While Loop

Loops were also originally constructed entirely from GOTOs, so the familiar while loop:

int times = 5;
while(times > 0)
{
  Console.WriteLine("Counting Down: " + times);
  times = times - 1;
}

Can be written:

int times = 5;
Test:
  if(times > 0) goto Loop;
  Environment.Exit(0);

Loop: 
  Console.WriteLine("Counting Down: " + times);
  times = times - 1;
  goto Test;

The do while and for loops are implemented similarly. As you can probably imagine, as more control flow is added to a program, using GOTOs and corresponding labels to jump to becomes very hard to follow.