Structured Program Theorem

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http://zimmer.fresnostate.edu/~sasanr/Teaching-Material/SAD/Process-Specification/Pseudocode.doc
2-Structured Program Theorem
https://en.wikipedia.org/wiki/Structured_program_theorem
to fully grasp the six basic computer operations and the Structure Theorem. Then:
1. Explain what a control structure is. The assignment is NOT “explain the three control structures.” Do not make any reference to the three specific control structures. Explain the general concept. This is a difficult task requiring thinking. Therefore … think! Use an analogy if that helps.
2. Explain the Structure Theorem in your own language in such a way that an intelligent junior high student would comprehend it. Do not copy/paste.
3. Consider the software program that runs the operations of an ATM. From the workings of (i.e., your external interaction with) the ATM, you can logically deduce certain conclusions about the internal workings of this program. Give an example from this software program for each of the following control structures:
• a. sequence
• b. selection
• c. repetition

Sample Solution

Control Structure

A control structure is a programming construct that allows programmers to control the flow of execution of a program. Control structures are used to make decisions, repeat loops, and jump to different parts of the program.

Analogy

Imagine you are driving a car. You can control the direction and speed of the car by using the steering wheel, gas pedal, and brake pedal. These controls are analogous to control structures in programming.

Examples

Some common examples of control structures include:

  • If statements: If statements allow programmers to make decisions based on a condition. For example, an if statement could be used to decide whether or not to display a message to the user.
  • Loops: Loops allow programmers to repeat a block of code multiple times. For example, a loop could be used to print all of the numbers from 1 to 10 to the console.
  • Jumps: Jumps allow programmers to jump to a different part of the program. For example, a jump could be used to jump to the end of a loop if a certain condition is met.

Importance of Control Structures

Control structures are essential for programming. They allow programmers to write complex and powerful programs. Without control structures, programs would be very limited in what they could do.

Structure Theorem

The Structure Theorem is a theorem in theoretical computer science that states that any program can be written using only three control structures: sequence, selection, and repetition.

Explanation for Junior High School Students

Imagine you are building a LEGO house. You can build the house by following a set of instructions. The instructions tell you what steps to take in order to build the house.

Control structures in programming are similar to LEGO building instructions. They tell the program what steps to take in order to complete a task.

The Structure Theorem states that any program can be built using only three control structures: sequence, selection, and repetition.

  • Sequence: Sequence means that the steps of the program are executed in order. For example, if you are building a LEGO house, you might first build the foundation, then the walls, then the roof.
  • Selection: Selection means that the program chooses which step to execute based on a condition. For example, if you are building a LEGO house, you might choose to build a red roof or a blue roof.
  • Repetition: Repetition means that the program repeats a step multiple times. For example, if you are building a LEGO house, you might need to repeat the step of building a wall multiple times.

Example

Here is an example of how the three control structures can be used to write a simple program:

// Sequence

if (age >= 18) {

// Selection

vote();

} else {

// Selection

waitUntilYouAreEighteen();

}

This program first checks if the user is 18 years old or older. If the user is 18 years old or older, the program calls the vote() function. Otherwise, the program calls the waitUntilYouAreEighteen() function.

The vote() function and the waitUntilYouAreEighteen() function could be more complex programs, but they would still be built using the three control structures of sequence, selection, and repetition.

Conclusion

Control structures are an essential part of programming. They allow programmers to write complex and powerful programs. The Structure Theorem states that any program can be written using only three control structures: sequence, selection, and repetition.

 

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