If a C program contains only one function, it must be __________.

Explanation:

Single Acting Steam Engine

Definition: A single acting steam engine is a type of steam engine where the steam acts on only one side of the piston during its operation, producing one working stroke per revolution of the crankshaft. This configuration contrasts with double-acting steam engines, where the steam alternately acts on both sides of the piston.

Working Principle: In a single acting steam engine, steam is introduced into the cylinder on one side of the piston. The pressure of the steam pushes the piston, converting thermal energy into mechanical work. After the steam has expanded, it is exhausted, and the piston is returned to its original position by a flywheel or another mechanism, ready for the next cycle.

Advantages:

• Simplicity in design and construction, making it easier to manufacture and maintain.
• Less mechanical complexity compared to double-acting engines, resulting in fewer parts and potential points of failure.

Disadvantages:

• Lower efficiency as only one side of the piston is used for performing work.
• Requires a more substantial flywheel to maintain smooth operation due to the intermittent power delivery.

Applications: Single acting steam engines are commonly used in smaller applications where simplicity and cost are critical factors, such as in some types of pumps and small locomotives.

Correct Option Analysis:

The correct option for a C program containing only one function is:

Option 4: main()

This is because in the C programming language, the main() function is the entry point of any C program. When a C program is executed, the execution starts from the main() function. This function is mandatory for every C program, and without it, the program will not run. The main() function can take arguments (usually for command-line inputs), but it must be present in every C program.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: primary()

This is not a valid function name in C that signifies the entry point of the program. While 'primary' might be used as a function name, it does not have the special significance or required presence that main() does.

Option 2: void()

This is incorrect. 'void' is a keyword in C that specifies that a function does not return a value. It cannot be used as a function name and certainly cannot replace main().

Option 3: major()

This is also incorrect. 'major' can be used as a function name, but like 'primary', it does not have any special significance in the C programming language. It is not the designated entry point of a C program.

Conclusion:

Understanding the role of the main() function is crucial for programming in C. It is the starting point of execution and is mandatory for every C program. Without the main() function, a C program cannot execute, which is why it is the correct option among the given choices.