Question

5.6 - Discussion: Should Loops be Well-Disciplined, or...

...Should Programmers be able to use “GO TO” statements as they please?

Some programming languages require that a loop only have one way in, and one way out; there are no “GO TO” statements. Other languages (like BASIC and FORTRAN) allow for statements to have “labels”, or addresses, that another statement like a GO TO can explicitly transfer control.

Discussion: What do you see as the strengths and weaknesses of each of these approaches? Would you rather work in a strongly disciplined language, that only lets you exit your loops by “falling out the bottom of them” when their control variable or interaction conditions say “I’ve had enough?” Do GO TO statements appeal to you?

Additionally, what special hazards might the programmer find when starting to combine IF, CASE, or other conditional logic on top of or inside of their loops?

Answer 1

The benefits of GOTO were as follows:

• It is functionally identical to an instruction found in all CPUs (and their assembly languages) - sometimes called JUMP/JMP or BRANCH (BR) - or even GOTO. It’s an unconditional change in program flow. It is as easy to implement in a high level language (like Fortran or C) as it is in assembly language, and is easy for a programmer familiar with assembly language to understand.
• It allows manual code-folding (which is still useful), such as entering cleanup code at various different places - or entering common initialization code.
• With GOTO and a simple IF <condition> STATEMENT form, you can implement other flow-control possibilities, such as IF/THEN/ELSE, loop exiting statements (like “break” in C), loop repeating statements (like “continue” in C/C++), and iterative loops.